4L80E or GV Overdrive for my '90 Suburban?

90Saburban

Junior Member
Joined
Feb 11, 2021
Posts
8
Reaction score
58
Location
Idaho
First Name
James
Truck Year
1990
Truck Model
R2500 Suburban
Engine Size
350 TBI
Hello all - me and my 1990 R2500 Sub are new to the forum. 5.7 liter TBI, 2WD, 4.10 gears, 170,000 miles. I'd like to add overdrive to the Sub at some point in the near future. Maybe this summer if I can source all the right parts. Love the TH400 for it's rock solid dependability but I really would like to go the speed limit on the freeway (80 MPH here) without spinning over 3,400 RPM. I usually try to stay right at 70 MPH which is still 3,000 RPM and after a while feels like I'm flying in a jet. I'd take any MPG gains of course but the primary goal here is modern drivability.

I've narrowed it down to two choices:

1. Add a 4L80E and EZ-TCU transmission controller - find shifter linkage that will work for the 4L80E (does the linkage from a 700r4 swap right over?), move cross member, shorten the driveshaft, etc.

2. Find a Gear Vendors overdrive unit and use that with the TH400. I believe the biggest alteration here will be to shorten the driveshaft to accommodate the GV unit.

For any of you that have done similar swaps, which would you choose? I don't currently tow anything, but I do see towing a car trailer with 3-4 four wheelers with it one day. I would like for whichever setup I go with to be AUTOMATIC - I'd prefer not to have to switch OD on or off. I'd like to spend $3,000 or less for the whole thing. Any more than that and I think I'll just keep driving 70 MPH and take the 2-3 MPG hit on economy. Maybe put in earbuds.

Thanks in advance for any advice or words of wisdom on this swap! Here she is for those that haven't seen her yet.

You must be registered for see images attach
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
1,675
Reaction score
2,189
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
If you have no plans to add more power, a properly built 700 is pretty cheap and easy swap. The 4L80 is expensive and way overkill.
 

PrairieDrifter

Full Access Member
Joined
Dec 28, 2014
Posts
2,315
Reaction score
1,711
Location
North Dakota
First Name
Mason
Truck Year
84,79,77,70,48
Truck Model
Suburban k10, bonanza k10, c30 C&C, c10, gmc 1/2ton
Engine Size
350, 350, 350, 350, 350
Blah... I would personally never swap to a 700. I think I would go gearvendors myself.

But you have to think about maintenance as well, like parts availability and whatnot, just for the long run. Other than the trans controller and maybe a shifter linkage the 4l80 is all gm and available pretty much anywhere. The gearvendors is a "one off" in a way so you'll have to source things from them, just something to consider.

But the gearvendors would be less work in my opinion. For something like your application would be perfect.
 

Curt

Full Access Member
Joined
Sep 11, 2017
Posts
631
Reaction score
1,054
Location
Carlsbad
First Name
Curtis
Truck Year
1984
Truck Model
K-30
Engine Size
383
I looked at gear vendors myself.After seeing a 4x4 squarebody truck with one installed,I decided against it.The angle of the drivetrain makes the gear vendor hang low,especially on the back of a transfercase.It’s expensive and I would think you’d wanna add a second cross member.

But,if you’re just looking for better mileage and lower hwy rpms,it would be the easiest option and way higher rated than a 700R4 on horsepower,towing.It’s good for 25000 gwvr
 

Frankenchevy

Lying Dog-Faced Pony Soldier
Joined
Jan 3, 2018
Posts
5,278
Reaction score
5,799
Location
USA
First Name
Jeremy
Truck Year
Square
Truck Model
CUCV
Engine Size
Small
A gear vendors would probably end up being more expensive than a 4l80. A rebuilt 2wd 4l80 is only $1400-1800 out here. A controller is $400 and your rear driveshaft may work.
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
2,856
Reaction score
2,785
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
I
A gear vendors would probably end up being more expensive than a 4l80. A rebuilt 2wd 4l80 is only $1400-1800 out here. A controller is $400 and your rear driveshaft may work.
I agree with this. It’s only about 1-1/2” longer than the TH400 and the shaft should work exactly the same. Just put a couple inches of lift on it and you won’t even have to mess with the driveshaft:33:
 

PrairieDrifter

Full Access Member
Joined
Dec 28, 2014
Posts
2,315
Reaction score
1,711
Location
North Dakota
First Name
Mason
Truck Year
84,79,77,70,48
Truck Model
Suburban k10, bonanza k10, c30 C&C, c10, gmc 1/2ton
Engine Size
350, 350, 350, 350, 350
I looked at gear vendors myself.After seeing a 4x4 squarebody truck with one installed,I decided against it.The angle of the drivetrain makes the gear vendor hang low,especially on the back of a transfercase.It’s expensive and I would think you’d wanna add a second cross member.

But,if you’re just looking for better mileage and lower hwy rpms,it would be the easiest option and way higher rated than a 700R4 on horsepower,towing.It’s good for 25000 gwvr
I agree on the 4x4 option, at least another crossmember, no blazers or short boxes. I would do a 4x4 crew cab or a cab and chassis truck with a gearvendors.

But OP's burb is 2wd and it wouldn't add much if any length, more than a transfer case on a 4wd
 

90Saburban

Junior Member
Joined
Feb 11, 2021
Posts
8
Reaction score
58
Location
Idaho
First Name
James
Truck Year
1990
Truck Model
R2500 Suburban
Engine Size
350 TBI
It probably all depends on what I can find for a good price, but right now I’m leaning toward a 4L80E/700R4 over the GV unit. This is largely because I think it will end up being quite a bit cheaper unless I find a good used GV unit for a good price. New GV unit is already $3,000 plus cost to modify driveshaft. It’s pretty common to find a used “working” 4L80E around here for $400-$600 but of course it’s condition will be largely unknown. Finding a rebuilt 4L80E for around $1500-$1800 may be the best option.

I checked the throttle cable bracket and there is an empty provision for a 700R4 TV cable and the TBI unit has the appropriate connector as well, so that could be an option too. I always have the option of building a 700 and that may suit my needs as I don’t plan to tow much. Seems like if going to the effort to do the swap the 4L80E makes the most sense.
 

BigDaddy72

Full Access Member
Joined
Jul 26, 2020
Posts
434
Reaction score
867
Location
Bentonville Arkansas
First Name
Travis
Truck Year
1974
Truck Model
C30 Chassis Cab
Engine Size
496
With your combination 700r will be more than adequate.

I’ve had 2 behind sbc’s Making 400 ft. Lbs. +

Neither one ever slipped or had any issues. Both of mine were good transmissions and just simple upgrades from stock.

One I had in a square and towed with it all the time. Never skipped a beat.

The other I still have in my 55 Chevy. I have tortured that one. It’s been in the car for 10 years.

I have a 4l60 (electronically shifted version of a 700r) in my 96 suburban that I have towed a 30’ enclosed trailer with many times 500 miles at a time. No issues.

They are not indestructible but they are not the junk people who never had a decent built one make them out to be.

If you did moderate towing and stuck with an engine that didn’t make more than 400 ish torque it would be a great “much cheaper option”

That being said anybody can break anything. All depends on how you use/abuse it and take care of and maintain it.

A 700 is cheap compared to a 4l80 or a gear vendor. Plus it has a deeper od than the gear vendor.

With your combo anything else as mentioned is overkill.

Do your research on how to properly set up the tv cable and you will get many years of good service from one.

No electronics needed to put one in if you run a manual lock up converter. Waaaayy cheaper than the other 2 options.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
25,597
Reaction score
13,919
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
Yes, the GV is going to have the highest initial cost, but that's all it is. Spend an additional 70 bucks to have your shaft shortened and balanced. It will be more expensive though if you ditch the carrier bearing setup and install a single shaft.

A trans swap will obviously be cheaper... potentially. But there's also a good chance to get nickel and dimed all the way past the expense of a GV and then still have the additional work of a trans swap. Especially if you get a used 80e and have to pull it back out and get it rebuilt shortly after. Or if you go the 700r4 route and have to pay to have it rebuilt 2 or 3 times because very few people can build one to be reliable.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
1,675
Reaction score
2,189
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
The 700/4L60 has been around long enough that any shop worth a dime should be familiar with them.

The 700 is pretty reliable up to 400-450ish torque, properly built. Put in a good wide band, upgraded 3-4 clutch pack, shift kit and some minor hard part upgrades, it will be fine. Put a cooler on it just to be safe.
 

1984dually

Full Access Member
Joined
Aug 31, 2013
Posts
208
Reaction score
31
Location
Malin OR
First Name
Danny
Truck Year
1984
Truck Model
C30
Engine Size
8.1L
My two cents. Current truck is a dually with a 4l80e. 3.73 rear gear and it pokes along at about 2000 at 75. Th400 with a gv would be higher as there is no converter lockup. One option is to find a Doug Nash overdrive unit. Usually you can find them in the 2-500 dollar range. Tough as nails(35000 gvw). Parts can be hard to find but bearing look to be off the shelf items. 700r4 would not be a good choice. Yes they can be built to handle a lot of abuse but every trans builder I’ve talked to will start backing up if you tell them you want to put it in a 6000 pound truck(especially pulling a trailer). If you never pull anything a 700r4 would probably work with a 350 engine. Me, I’m pulling my 4l80e and installing a sm465 with a Doug Nash overdrive unit. I do a lot of pulling and like the idea of splitting gears.
 

idahovette

Full Access Member
Joined
Aug 7, 2016
Posts
4,170
Reaction score
7,154
Location
Weiser Idaho
First Name
Perry
Truck Year
1975-1979
Truck Model
K20-K10
Engine Size
350
@90Saburban , don't know where you are located, if in the Boise area the guys at Ultimate Transmission in Garden City are great trans experts. They can give you any kind of build and guide you as to what you need. Have a 2004R they did for my Nova, 700R4 for my Nomad and a 700R4 for my Grandson
 

BigDaddy72

Full Access Member
Joined
Jul 26, 2020
Posts
434
Reaction score
867
Location
Bentonville Arkansas
First Name
Travis
Truck Year
1974
Truck Model
C30 Chassis Cab
Engine Size
496
I wouldn’t put a 700 in a dually pulling heavy loads.

Then again a sbc wouldn’t be the right choice for a dually pulling heavy loads either.

Best factory manual od is the nv4500. They are in the k3500 dually (later model of course) and in a dually a gv with a th400 is a grate choice so is a 4l80.

I currently have all three. Have used all 3 and have and have used 700r.

A 700 (built correctly) will be more than adequate in a sbc 2wd Suburban.

My suburban is a vortec 350 with 4l60. Very well matched combination.

Are they the strongest no
Would I put one in either one of my duallys no.

My duallys have nv4500 and th400 in my other dually that I will put a gv in.

I like them all and in my experience with each one they all have their application.

No one has given bad advise.

You have to remember one thing too.

700 has lower first gear and robs less power to run than th400 or 4l80.

The suburban will get better fuel economy and have/feel like it has more power behind a sbc.

Let’s face it if he’s towing a bunch he needs a different tow vehicle anyway. Like a 1 ton bbc equipped tow rig. A dually or diesel.

But the op didn’t ask about a 700 he asked 4l80 or gearvendors.

The answer is either will work absolutely fine in your application.

They both have pros and cons one compared to another but are very equal in strength and reliability and cost. Personal choice my opinion... now my book is finished lol!!!
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
25,597
Reaction score
13,919
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
I wouldn’t put a 700 in a dually pulling heavy loads.

Then again a sbc wouldn’t be the right choice for a dually pulling heavy loads either.

Best factory manual od is the nv4500. They are in the k3500 dually (later model of course) and in a dually a gv with a th400 is a grate choice so is a 4l80.

I currently have all three. Have used all 3 and have and have used 700r.

A 700 (built correctly) will be more than adequate in a sbc 2wd Suburban.

My suburban is a vortec 350 with 4l60. Very well matched combination.

Are they the strongest no
Would I put one in either one of my duallys no.

My duallys have nv4500 and th400 in my other dually that I will put a gv in.

I like them all and in my experience with each one they all have their application.

No one has given bad advise.

You have to remember one thing too.

700 has lower first gear and robs less power to run than th400 or 4l80.

The suburban will get better fuel economy and have/feel like it has more power behind a sbc.

Let’s face it if he’s towing a bunch he needs a different tow vehicle anyway. Like a 1 ton bbc equipped tow rig. A dually or diesel.

But the op didn’t ask about a 700 he asked 4l80 or gearvendors.

The answer is either will work absolutely fine in your application.

They both have pros and cons one compared to another but are very equal in strength and reliability and cost. Personal choice my opinion... now my book is finished lol!!!

But we have come to no conclusion, lol. Other than they are all potentially good options for what we are assuming is the intended use.
 

Forum statistics

Threads
35,534
Posts
747,415
Members
24,453
Latest member
jbengfort
Top