4L80E Information Thread

[NickTransmissions]

Starting a 4L80E information thread for those that want to learn more about this transmission (the best GM ever produced in my humble opinion), considering it for a resto-swap into a Squarebody truck or K5 Blazer (or anything for that matter) and/or considering taking on a rebuild of this transmission.

The information contained within this thread has been collected from a variety of sources, including the 4L80E Automatic Transmission Service Group manual, How to Build and Modify 4L80E Transmissions for Performance, various internet forum posts by validated subject matter experts in the industry as well as my own first hand experience and knowledge. A complete ‘works cited’ can be found at the end. I am hoping this can be an easy 'one-stop shop' for information, guidance and advice as it relates to these transmissions.

I'll update with more information as I collect it and revise any inaccuracies that others raise and that I can verify.

Family Production Run: 1991-2014
Variants: 4L80E, 4L85E
Gas Applications: GM Trucks, SUVs and some HiPerf passenger cars (Corvette, Camaro)
Diesel Applications: Some Duramax-equipped vans (4L85E)
Predecessor Transmission: TH400, TH475
Follow-on Transmission: 6L90

4L80E Gear Ratios

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Fluid Capacities

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4L80E Application Chart
An application chart is intended to inform what mechanical elements are working or not working inside a transmission while it’s in a given range and gear. Range is what is selected on the column shifter and includes Park, Neutral, Drive, etc while gear is what specific gear as defined by engine revolution to output shaft revolution ratio. Examples include 1st gear, 2nd gear, 3rd gear and so forth.

You can narrow down and in some cases, pin-point the source of drivability symptoms by simply looking at a range chart and comparing what the chart is telling you to your symptoms in terms of when/where in the shifting cycle they are happening.

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Identifying Year of Production
Identifying the year of production is important for a variety of reasons including fitment and compatibility for swaps, internal hard part replacement, computer calibration and programming and others. GM provides two methods for determining what year and application a given 4L80E was manufactured. The first is the large date stamp sticker on the raised rectangular embossment on the passenger side of the case, below the cooler line area. It contains a 4-character alpha-numeric code that informs the year and application of the vehicle. The second method is using the metal ID tag secured to the rear passenger side of the case via a rivet. It will have a three-character code along with other information that provides year and application.

ID tag and sticker - 1995 unit (left) and ID tag and sticker - 2006 unit (right)

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Number = Year of production (distinguish between 1990s and 2000s via the presence or absence of a bell housing bolt hole location at the 12-o’clock position.
Alpha-3 Digit Code = Application (model, sub-model)
GM Goodwrench Remanufactured Units: These units replaced the OEM factory tag and stamp with a GM Goodwrench green ID tag and sticker which is typically placed onto the bell housing

Electrical and Electronics Testing

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Rebuilding the 4L80E - Video Instruction
Stock-Mild Performance Rebuild

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High Performance Street/Strip Rebuild

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Valve Body Assembly and Testing

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Teardown and Inspection

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Generations, Engineering Changes and Interchange Information
4L80Es come in two distinct generations, First and Second generation. Each of those consists of a few vintages so knowing the specific year of production for your 4L80E will be very helpful if / when you need to either overhaul the unit or look for a compatible replacement on the used market. The table below summarizes the important changes, interchange guidance as well as relevant links if available.

Table is not 100% exhaustive; it’s intended to convey the most important and notable changes that would be material when it comes to making decisions on swaps, acquiring replacement parts or procedural direction.

Gen	Vintage	Defining Characteristics	Interchange Information	Notes	Link to More Info (If Applicable)
1st	1991-1993	First generation electronic pressure control solenoid (vented), produced by Bosch, valve body, accumulator body, torque compensator valve (accumulator body), separator plate and case are specific to this vintage of 4L80E 4WD Units - used three speed sensors to facilitate transmission control: input speed, output speed and vehicle speed (transfer case); these units had the reluctor gear pressed onto the output carrier assembly like 2WD units.	Any 1991-1993 4L80E will interchange with any of those years w/in the vintage as long as it has the torque compensator valve and corresponding valve body and spacer plate. You can adapt these units to accept a L93-03 Borg Warner EPC by drilling an EPC vent hole in the applicable location in the valve body (see Transgo's instructions, linked at right). The wiring harness also changed in 1993 however Rostra’s harness will service all years 1991-2003	Traditional rear gear train lubrication design; transmission cooler line fittings for supply and return located behind the bell housing on passenger side EPC operates at 292.5 Hz WARNING - DO NOT install Transgo's pressure relief valve mechanism as it can stick open/jam and result in massive hydraulic pressure losses inside the transmission!!! Mitigate high line pressure risk by replacing the boost and pressure regulator valves with Sonnax equivalents. If installing Sonnax's line-to-lube pressure regulator valve, DO NOT DRILL the .055" line-to-lube hole in the pump cover as Transgo instructs in their literature.	Transgo SK4L80E Instructions
1st	1994	Stand-alone year; first year of new EPC design (Borg Warner); valve body, separator plate, case, wiring harness and EPC all changed. Accumulator housing redesigned to eliminate torque signal compensator (TSC) valve; TSC port in spacer plate eliminated. 4WD Units - eliminated the rear speed sensor reluctor gear on the on the output carrier assembly; 95-96 may or may not have speed sensors installed but if so, they are non-functional	Technically, this year will not interchange with any other year without modification/adaptation. Cannot be prospectively installed into any 1995+ application as it lacks mounting locations for the manual lever position sensor (MLPS) on the case by the gear selector.	Traditional rear gear train lubrication design; transmission cooler line fittings for supply and return located behind the bell housing on passenger side. EPC operates at 614 Hz - all years 1994+	NA
1st	1995-1996	First year for manual lever position sensor (MLPS) on selector shaft Last years of first generation valve body w/front-to-back lubrication transfer pipe	Will retro to earlier years as a complete transmission, except for 4WD units in 1991-1993 vehicles/applications as those units will require the reluctor gear to be pressed onto the output carrier to ensure proper function. First generation valve body assemblies will not prospectively install onto 2nd generation cases (1997+)	Traditional rear gear train lubrication design; transmission cooler line fittings for supply and return located behind the bell housing on passenger side	NA
2nd	1997-1998	First year of rear-gear train lube redesign; return cooler line fitting relocated to center support to lube gear train 'first' First year of 2nd generation valve body assembly; front-to-back lube transfer pipe replaced with shorter, narrower transfer pipe from rear valve body/AFL to case rear bushing. Low-reverse servo assembly and servo cover changed; previous design had a flat top while 2nd gen design had a hump; pin lengths changed as well Pump body redesigned; pump cover aka stator support redesigned Bonded steel/rubber pistons (National Seal) introduced into forward, direct drums Heavy duty 34-element sprag assembly introduced to replace first design int. roller assembly (16-element); spiral-lock snap ring for int. sprag introduced	Will retro to earlier years as a complete transmission provided that compatible cooler lines are installed 2nd generation valve bodies and spacer plates will not retro to 1991-1996 4L80Es 2nd generation pump body casting will retro to earlier years however first design pump body casting (1991-1996) will not prospectively mate to a 2nd generation pump cover/stator assembly. Pump covers must remain with their respective generations of 4L80E. 1st gen pump cover will not prospectively install onto 97+ units; 1997+ pump covers will not retro to earlier units. 1997+ direct drum assembly, including bonded piston/return spring assembly and 34-element intermediate sprag/race will retro to all previous years as well as all years TH400/TH375B/TH475 Spiral-lock snap ring will retro to earlier years 4L80E individually as well as all TH400 variants	Updated rear gear train lube design to align with new 'center lube' strategy which feeds return oil directly to the center support and gear train to mitigate heat or lube-related failures (and warranty costs). CAUTION: GM developed a replacement stator/pump cover assembly for use in 1991-1996 4L80Es that looks very similar to the 97+ stator/pump cover in the lube area however this replacement cover is not drilled in that location like the 97+ covers thus makes it incompatible with any 4L80E manufactured in 1997+	ATRA Webinar Handout see pgs 14-39 ATRA Webinar Handout, page 24 (Replacement pump, 91-96)
2nd	1999+	Gear train redesigned to accommodate a design change which increased pinion gear height for both planetary carrier assemblies by 10% over previous years' design; .041 shim added to sun-gear-to-rear planetary assembly thrust bearing stack Bell housing bolt pattern updated to incorporate a transmission-engine block bolt hole location at the 12-o'clock position for mounting to Generation 3/4 small block engines (LSx) Manual 2nd gear band widened to 2.730" from previous design width of 2.530"; servo apply pin lengthened to accommodate band design change.	Gear train will interchange with 1997-1998 transmissions as a service pack (service pack = entire gear set from the center support to the output shaft and everything in between) Individual components (sun gear, planetary carrier assemblies, shaft, etc) WILL NOT interchange! 1999+ 4L80E complete transmissions will interchange back to 1997 and 1998.	1999+ gear components are a lighter shade of brown to distinguish them from 1997-1998 gear components. Additionally, gear train components have identification grooves machined into the splines/teeth for identification.	ATRA Webinar Handout see pgs 14-39
2nd	2001+	Overdrive roller clutch design change to smaller, narrower rollers; OD roller assembly outer race inner diameter reduced to accommodate roller OWC design change. Inner cam ramp angle on coast clutch drum as well as return spring assembly and return spring assembly snap ring also updated per new design. Input shaft redesigned to have forward clutch feeds on both sides of input shaft instead of just one side in the first design.	You can swap all parts mentioned at left as a matched set into earlier units but individual components will not retro.	Many builders, including me, prefer the earlier design with the larger rollers for high performance applications hence making 1997-2000 cores a little bit more preferable over 2001+	ATRA Webinar Handout
2nd	1997-2007	Two distinct case castings were placed into production during these years: Type Two and Type Three. The 'Type' is differentiated by the design features on the pump assembly-to-case mating surface on the case by the transmission cooler supply line. A 'Type One' case is considered any case manufactured between 1991-96 for a first gen 4L80E.	In 2004, cooler line return port in the pump was eliminated and corresponding location on pump-case mating deck surface was recast to mate flush with the pump whereas in 1997-2003 cases, this area on the deck surface contains a step (1991-1996 cases contain cooler lube port locations for supply and return fluid). To characterize this change, three different case types are described: > Type One case (1991-96; has both port locations) > Type Two case (1997-07; has only one port location, features flush deck surface) > Type Three case (2004-2007; has only one port location, features stepped deck surface) Interchange rules: * 1991-1996 pump assy onto a Type One case: will work as is; DO NOT install a 91-96 pump assy onto a Type Two or Three case (97+) * 1997-2003 pump assy onto a Type Two case: will work as is * 2004-2007 pump assy onto a Type Two or Three case: will work as is * 1997-2003 pump assy onto a Type Three case: plug return cooler line port in the pump cover - this is the cooler line port that is closest to clutch feed ports on the pump cover	As noted above, a 1997+ pump body will retrospectively mate to a 1991-1996 pump cover and function normally in those first gen transmissions.	Transgo Publication 06-177-4L80E
2nd	2004+	Wiring Harness and EPC changed to a cube-shaped connector on each component; manufacturer changed from Borg Warner to Bosch	Will retro as a matched set
2nd	2004+	2WD Units Only - extension housing bushing outer diameter increased, resulting in ext housing inner diameter increase	Will retro to earlier units with the matching bushing	Bushing is available OTC everywhere trans parts are sold

4L80E Overhaul Components and Parts (Minimum Viable Rebuild)

• Cal Kit (Filter, paper/rubber, bonded pistons, front band, pump body bushing, extension housing bushing (2004+ require a different bushing, sold separately by Durabond/AC Delco)

4L80E Updates and Upgrades for Performance

Update / Upgrade	Rationale	Additional Information
Borg Warner EPC retro to 1991-1993 vehicles	Early Bosch vented EPC for 91-93 units is no longer available	Valve body will need to be drilled .125" to vent as early VBs were not ported like 1994+ valve bodies.
AFL valve - upgrade to either Sonnax or Central Valve Bodies drop in	AFL valve and bore wear is common on higher-mileage units and results in poor performance, premature applied element failure, especially in heavy duty and high perf applications.	The Sonnax AFL valve replacement kit requires the bore to be reamed via the Sonnax bore and reamer kit for the 4L80E AFL (also requires the jig and holding fixture, sold separately) Central Valve Bodies valves are drop-in; no machining or reaming required
Sonnax 1-2 and 2-3 shift valve spring kit	These springs can be worn in higher mileage units and provide insufficient spring tension to stroke the valves as needed.	No machining required
1-2 accumulator valve spring	This spring regulates how much accumulator fluid is allowed to enter the accumulation side of the 1-2 accumulator piston and changing the spring to a performance spring will reduce accumulator fluid flow, enabling a slightly quicker 1-2 shift, all other things equal.	To my knowledge, these springs are only available in shift kits sold by Transgo, Superior Technologies, Fairbanks and others.
Sonnax TCC Regulator Valve replacement	Worn TCC Regulator valves result in converter clutch slippage and burn-up; DTC P1870 (earlier OBD2) and P0894 (later OBD2) will set	These DTCs are more commonly associated with converter failure and will usually not set until the TCC Reg valve bore has worn to the extent it's affecting the converter clutch
2-3 and 3-4 accumulator block off plate	Block the 2-3 and 3-4 accumulators when running a very high stall converter and dual-feeding the direct clutch as too much accumulation will slow shift time to dangerous levels, resulting in clutch slippage and burn-up under WOT shifts in high power applications.	Block plates can be purchased from CK Performance or other speciality transmission retailers.
Transbrake	Trans Brakes are used in drag racing applications and require numerous modifications and changes to be made elsewhere in the transmission to support their integration into the unit. Each transbrake manufacturer will provide a detailed set of instructions for the builder to follow when installing a transbrake onto the transmission. These instructions will vary based on manufacturer and transbrake design.	There are many trans brake manufacturers on the market
Separator plate feed hole sizes	Drill out the separator plate feed hole sizes for 1-2, 2-3 and 3-4 shifts per your vehicle's application, weight, rear gearing, converter stall and engine power as needed.	Specific guidance upon request but generally, I go .080, .095, .085 for 2nd, 3rd and 4th respectively for converters with stalls between 2400-2900 and incrementally larger based on margin of stall speed increase of those figures
Case check balls	Leave the following check balls out for firmer shifts: 1. 2-3 accumulator check ball (not needed if dual feeding and blocking 2-3/3-4 accumulators) 2. Reverse check ball	Keep 2-3 acc check ball if 2-3 accumulator is active and direct clutch is not dual fed (i.e a stock direct clutch circuit set up)
Lube modifications (pump, direct drum, center support, coast clutch drum)	Promotes and enables better oiling to gears, sprags, shafts and other vital areas	See my 4L80E lub mods on Youtube for details and step by step instructions
Sonnax LB-4L80E Boost Valve and spring kit + Sonnax Line-to-Lube Pressure Regulator Valve	High line pressure can occur when either the Boost or PR valves wear to the extent they begin to stick wide open (particularly the boost valve) and should always be replaced on overhaul with Sonnax components	Transgo also makes boost valves that come in their shift kits but I prefer the Sonnax parts as they can be purchased individually from any other parts. The Sonnax pressure regulator spring provides approximately 10% more pressure linearly over the stock spring, which is still safe for otherwise stock or mild performance applications. Other steps have to be taken to mitigate high-line pressure damage if a more powerful spring is used.
Pump reconditioning	4L80E pumps are generally in good shape however pump gear-to-body deck surfaces must be checked to validate everything is good to go as-is. If clearance is excessive or uneven, but crescent is not worn, mill pump body as required and install new gears. Re-surface pump cover at this time to ensure all working surfaces are in good shape.	If crescent is worn, pump will not generate pressure and volume flow nearly as efficiently and a replacement pump assembly should be sought See my 4L80E Pump Gear Clearances video for instructions
Pump Drainback	Drill all 4L80E drain back ports to .250 to facilitate better drain back and prevent front seal blow out	Front seal blow-out seems to be more common in the first gen 4L80Es (91-96) compared to 2nd gen, 97+
Clutch Module	The TH400 and 4L80Es aren't too fussy when it comes to clutch material. Stock frictions will work up to about 600 HP then you will want to swap to a better clutch disc, such as Alto Reds, Raybestos GPZ, Stage One or Alto Kevlar-impregnated high energy. Kolene flat steels are also recommended in very heavy duty applications, regardless of what clutch is selected.	Alto Reds and Raybestos Blue Plates are designed primarily for drag racing, meaning they are optimized to hold super well for very short periods of working time. High energy and other similar materials are more optimal for heavy duty where lots of working, shifting, idle time and other strenuous use is anticipated. Raybestos Blues and Alto Reds do not absorb as much fluid as BW and other high energy clutches in my observations.
Oversized bushing (Omega Machine, Sacramento, CA)	An oversized bushing for the forward drum provides more contact surface area for the OD planet's journal thus more stability and reduces bushing wear due to 'rocking' between journal and bushing	Omega Machine - Forward Drum Bushing
Billet Input Shaft (early or late designs)	Recommended for applications in excess of 800 HP or 6500 RPM to prevent catastrophic failure and break up of OEM shafts.
Billet rollerized forward clutch hub	Recommended when horsepower levels exceed 500 and/or RPMs regularly exceed 5500.	Numerous manufacturers of these hubs exist, some are rollerized, others are not.
Sleeved Forward Drum	Many forward drums come in for overhaul with deep grooves cut into the inner diameter by the sealing rings on the rear of the input shaft. If the wear is pronounced enough, delayed engagements and slipping in forward/1st gear will result. Ream and sleeve the bore with a ductile iron insert to repair or proactively strengthen this area of the factory drum.	Requires drill press or mill w/reamer and hydraulic shop press to install the sleeve; sleeves are available from a variety of places.
Billet Forward Drum	Recommended for applications in excess of 800 HP/6000 RPMs to reduce likelihood of structural failure in OEM drum under extreme RPMs or high horsepower applications.
Direct Drum - Internal Dual Feed	More than doubles appy surface area for increased holding power in 3rd gear for higher power street strip or racing applications	Procedure 1. Leave drum lip seal out 2. Delete 2nd from top sealing ring on center support 3. Plug high-reverse passage in case using 3/8" cup plug - use loctite on outer diameter of plug 4. Block off 2-3 and 3-4 accumulator via block-off plate 5. Drill feed passage to .090-.095 for 2800-3200 stall applications, drill it larger if stall is higher
Direct Drum - High Rate Return springs	Prevents centrifugal apply in moderate to serious power applications	Full race applications should also receive a .050-.065 bleed hole in the drum to further mitigate centrifugal apply in 1st and 2nd gear
Direct Drum - Kolene coated backing plate	Reduces likelihood of slippage and burn up at WOT under very high horsepower	Available from CK Performance
Direct Drum - BIllet aluminum piston and return spring kit	Recommended for applications in excess of 800 HP/6000 RPMs to reduce likelihood of structural failure in OEM piston
Direct Drum - Billet Super Drum w/36 element intermediate sprag one-way clutch	Recommended for applications in excess of 1000 HP and/or 6500 RPMs reduce likelihood of catastrophic failure/break up of OEM drum under extreme RPMs
Intermediate Clutch snap ring	Replace the stock snap ring with one from a Chrysler 727 or A518 (46RH/RE/47-48RE) forward or direct clutch drum. There are five or six different thicknesses available but I use .088-.110 most often in TH400s and 4L80Es. The Chrysler snap ring is beefier and will last longer, not pop out under high power or load.	Keep clearance between .030-.050 in this clutch Transgo includes a thicker snap ring in its HD2 kit (I avoid that kit like the plague due to issues w/their separator plates and pressure relief mechanism)
Intermediate Clutch high rate return springs	Use these in high performance applications when RPMs are expected to exceed 5000 on a regular basis to prevent centrifugal apply in 1st gear and for a better 2-1 downshift	Can be sourced from CK Performance
Billet intermediate apply piston	Use when power levels exceed 800 horsepower and/or 6000 RPMs and avoid catastrophic failure of the factory piston.	Can be sourced from CK Performance
Sonnax Case Saver	Used in very high horsepower applications when line pressure has been increased significantly over factory levels; protects case lugs from blow out and prevents intermediate clutch snap ring failure	Sonnax case saver design retains the use of the breaking band (front band). There are two different designs, one for early 4L80Es (91-98) and all TH400s and a second version for 99+ 4L80Es
Cryogenically treated gears and shafts	It is a good idea to install cryogenically treated gear sets and shafts in units that may see 1000+ horsepower and/or 7000+ RPMs in a street strip or full race application.
Rollerize rear case	Eliminates a static thrust surface, keeps fluid cooler and reduces horsepower loss (a bit very slightly). Parts needed: 1991-1996 4L80E Pump Body Bushing TH350 pump body bearing and shim pack	Procedure 1. Measure the combined thickness of the three-tab steel selective washer in the rear of the case and 4-tab babbit washer that goes on the base of the output ring gear - write that number down 2. Acquire a later TH350 pump bearing and a set of end play shims for the same and measure the combined thickness of one shim and the bearing - compare to the above measurement 3. Swap shims until you get a similar measurement 4. Install the early 4L80E pump body bushing into the rear of the case so that appx one-sixteenth to one eighth of an inch protrudes into the case - this will enable the bearing to locate and center itself 5. Install shim then bearing into the case (black side of bearing faces down) then install the entire gear train (leave both thrust washers out of the case) and center support snap ring - do not install center support bolts 6. Measure gear train end play - result should be between .006-.012 (book spec is .003-.017) but I keep to a narrower range 7. Swap shims until you get a figure that is at least within book spec

Works Cited
- Automatic Transmission Rebuilders Association. “2000 Technical Seminar.” Automatic Transmission Rebuilders Association, 2000.
- Automatic Transmission Service Group Manual. ATSG 4L80E. 2nd ed., vol. 1, Cutler Bay, Florida, Automatic Transmission Service Group, 1991. 1 vols.
- Transgo. “06-177 4L80E Pump to Case matching– wrong match burns down unit “lack of lube.”” Transgo.com, Transgo, 30 October 2023, https://www.transgo.org/demo/06-177-4L80E Pump to Case matching.pdf. Accessed 30 December 2023.

 

[dragstews]

Starting a 4L80E information thread for those that want to learn more about this transmission (The best GM ever produced in my humble opinion), considering it for a resto-swap into a Squarebody truck or K5 Blazer (or anything for that matter) and/or considering taking on a rebuild of this transmission.

!! THM 400 on steroids !!

... Like a rock ...

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Or a tank ..