eBay drop out L8T mated to 6L90E thoughts and/or drivetrain suggestions.

[KnockingDiesel]

Hello,

Anyone have any experience with these drop out drivetrains?

$10k for an engine/trans/ecu/harness seems pretty reasonable considering most have under 50mi on them and lots with single digit odometer numbers.

I have 1985 3+3 dually 2wd Silverado I’m building no rust on the cab anywhere. 454 rebuild $4k and th400 $1500 but still no OD, so 4l80e rebuild and swap is closer to $3500 and GV overdrive is about the same. So to make it highway worthy I’m looking at $7.5k to $8.5k running a carbed BBC.

I understand that $10k doesn’t include mounts, modifications, driven accessories, electrical, etc. But it still seems reasonable since 100k + l96/6l90 combos are $7k to $8k.

My goal for this truck is to be able to reliably drive anywhere I want in the country at 75 mph while getting over 10 mpg. I would also like to be able to pull larger trailers (10k lbs) within 150-500 mi and lighter trailers (3-7k lbs) longer distances I accept poor towing economy. I am open to suggestions if I can achieve this with a 6.0/6.2/L8T. I’d like any real world experience with this.

The only experience I have with this is a Penske 18’ box truck L8T and 6l90 pulled a house full of furniture and rcsb truck on Penske flatbed like nothing. I did the drive (Phoenix to Albuquerque 450mi) with my 7.3 powestroke (cclb drw 4.10) and a large car (s430 MB) the Penske truck did better everywhere except fuel economy but the offset of diesel cost made fuel expenses a wash. Not to mention the Penske truck unloaded was peeling out in az from a stop.

I’m not really interested in diesel swap or manual trans. I am serious about this build to the point where I sold all other projects/not buy new ones, to focus on this. I’d like to go into it as well informed as I can. I like the idea of a 6 speed and 3.73 or 4.10 gears.

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[bucket]

You'll have to forgive folks like myself that can't keep track of all the newer variations... but what is an L8T? Is that the newer 6.2 used in the heavier trucks and vans?

 

[Nasty-LSX]

10k is high

 

[KnockingDiesel]

You'll have to forgive folks like myself that can't keep track of all the newer variations... but what is an L8T? Is that the newer 6.2 used in the heavier trucks and vans?

It is the 6.6L gas engine based on the new LT platform, replacing the L96 6.0 in HD trucks. Around 400hp and 450tq, mated to the 6l90E 6 speed auto.

 

[KnockingDiesel]

10k is high

$10k is a lot l but GM connect and drive LT1/8l90 is twice that with a 2yr/50k warranty. And it doesn’t include accessories like brackets for alt/power steering/water pump/fan/etc.

Factor in that a rebuild locally with cam and domed pistons to bump compression is $4k and 6 months waiting and $3500 for 4l80E. So I figured mounts are $300, harness mods $600 other miscellaneous stuff $1k and $8900 for engine/trans l, that’s $3200 more for a reliable modern drive train designed for heavy duty use, seems reasonable to me.

Also the 454 build with shop I spoke to is about 310hp 400tq the L8T is 401hp and 460tq of which 400 is available at 2k rpm

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[TotalyHucked]

That's not a bad price at all, I'd jump at that. I know a good bit about LS's and swapping them in but I know almost nothing about the LT engines. Check out Tejas Steelworks, that's where I got my engine mounts/trans mount/fan shroud from for my LS swap. Then check out both PSI Conversions and BP Harness, either makes good harnesses for swapping these trucks and that way you can keep the GM computers. Hopefully you can use the OE accessory drive as well.

 

[KnockingDiesel]

That's not a bad price at all, I'd jump at that. I know a good bit about LS's and swapping them in but I know almost nothing about the LT engines. Check out Tejas Steelworks, that's where I got my engine mounts/trans mount/fan shroud from for my LS swap. Then check out both PSI Conversions and BP Harness, either makes good harnesses for swapping these trucks and that way you can keep the GM computers. Hopefully you can use the OE accessory drive as well.

Yeah it’s a decent deal. 6.0 was my initial thought but it’s not much cheaper than the LT and it’s down almost 100tq to the L8T. I’m still considering the 6.0 since LS swap stuff is cheaper, readily available and all the bugs are worked out. I considered the 6.2 but since I will be towing I’m not sure it’s the best option. But even then 50k-100k mile 6.0/6.2 6 speed are $7k-$8k.

The way that 6.6 moved an unloaded penske truck was unreal, light up the tires or slide at will, in AZ. Even in Albuquerque at 5500ft I humiliated my cousins 5.3 crew cab.

 

[TotalyHucked]

Yeah that's wild. I haven't driven an L8T truck yet but would certainly like to. It's all relative, really. Knowing what I know now, I would've gone a different route. I paid a little more for a low mile 5.3/4L65 pullout and it's been fantastic but for what I ended up having in the whole thing, I could've put together my own 6.0 stroker for about the same. For factory reliability, that L8T package is going to be hard to beat and will last for many, many years.

 

[bucket]

310 hp on a 454 build is basically just a stock engine. 450+ hp is pretty dang easy on a mild build that suits a truck well.

With that said, as long as the newer drive train can be swapped in without hackery and proper tuning is done, it should be fantastic. It's hard to beat factory engineering.

 

[KnockingDiesel]

310 hp on a 454 build is basically just a stock engine. 450+ hp is pretty dang easy on a mild build that suits a truck well.

With that said, as long as the newer drive train can be swapped in without hackery and proper tuning is done, it should be fantastic. It's hard to beat factory engineering.

Install seems pretty straightforward, I found a bracket kit for engine, trans and power steering mounts. From what I see it’s a bit close to the master cylinder but not an issue for me since I’ll retain the hydro boost.

I’d love to keep the 454 but I want fuel injection, I’m not interested in TBI and I don’t see good reliability with the aftermarket stuff. So that leaves finding a vortex 7400 donor. All said and done I’m looking at $10k-$12k no matter what I do. So the L8T keeps coming out on top.

My truck is a camper special so 10,000lb gvwr and has 17,000lb gcwr and I’d like to have a drive train that’s built for that, the 6.0/6l90e with 4.10 was rated at that but L8T is over that with 3.42 gears.

So I’ll be switching the rear end to 3.73 maybe even go down to 3.54 (Dana 70).

Squarebody Gen V (L83/L86) Conversion Kit – Tejas SteelWorks, Inc.

tejassteelworks.com

 

[wuznme]

The ECU from that purchase will not work (no tuning options without high cost to unlock ECM) you will have to get a E38 ECM. That E38 may or may not work with the 6L90e, matching those up is not impossible just tricky. If moving forward with the L8T, try to get one from a truck not a van it saves cost on replacing the van specific items ie.. dipsticks & fill tubes.

 

[KnockingDiesel]

The ECU from that purchase will not work (no tuning options without high cost to unlock ECM) you will have to get a E38 ECM. That E38 may or may not work with the 6L90e, matching those up is not impossible just tricky. If moving forward with the L8T, try to get one from a truck not a van it saves cost on replacing the van specific items ie.. dipsticks & fill tubes.

Thank you for the info. There are lots of L8T Silverado/sierra. The tuning I was figuring on paying to unlock the exam $700 but if I can do it with an E38 would be great.

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[KnockingDiesel]

The extra cost and complications are leaning me away from this set up. Spear tech wants $4k for computer and harness mods to retain cruise control, tow/haul and manual shift.

All in $16k-$17k for the L8T/6L90E.

Currently exploring the L96/6L90E 360hp/380tq, lower mileage combos are $5-$6k range. I can get the the cruise control, tow/haul and manual shift, installed in the truck with mounts, crossmembers and exhaust for under $10k.

The Vortec 7400/4L80 290hp/410tq is not out of the question either. I can get a whole runner truck for $2500 and rebuild the 454 $3500 and the 4l80 $1500 and it’s all drop in. The vortec 7.4 is 4 bolt and full roller too.

I’d like the L8T 401hp/460tq but I don’t know enough about it to pull the trigger on a price tag that steep.

I think I’m gonna try to drive all 3 setups in heavy trucks, I got few months to decide.

 

[Bextreme04]

The extra cost and complications are leaning me away from this set up. Spear tech wants $4k for computer and harness mods to retain cruise control, tow/haul and manual shift.

All in $16k-$17k for the L8T/6L90E.

Currently exploring the L96/6L90E 360hp/380tq, lower mileage combos are $5-$6k range. I can get the the cruise control, tow/haul and manual shift, installed in the truck with mounts, crossmembers and exhaust for under $10k.

The Vortec 7400/4L80 290hp/410tq is not out of the question either. I can get a whole runner truck for $2500 and rebuild the 454 $3500 and the 4l80 $1500 and it’s all drop in. The vortec 7.4 is 4 bolt and full roller too.

I’d like the L8T 401hp/460tq but I don’t know enough about it to pull the trigger on a price tag that steep.

I think I’m gonna try to drive all 3 setups in heavy trucks, I got few months to decide.

I got my donor 97 K2500 Suburban for $500. Running and driving. The interior was completely shot and the suspension was falling apart, but I drove it home and parked it to strip it for the swap. I probably made ~$1000 in selling the parts I didn't need back on it. Rebuild prices for engine/trans is pretty accurate. You can do an 0411 swap to run the L29 and can basically tune it for free if you have a tool that can communicate. I use the OBDxPro VT, but there are others for cheaper. Its $100 for the HP Tuners credits, or ~$60 for a wireless/BTE tool, or like ~$15-20 for a wired tool to communicate. Tuning tools are free at that point. You can read/write with PCM Hammer or LS Droid and tune with TunerPro RT or Universal Patcher.

I also got an L9H and matching 6L80 with the E38 ECU and harness about 6 weeks ago locally for $1500. Trans is toast(that's why it was being sold), but engine was in great shape. I pulled it down anyways for the cam/valvetrain upgrade and decided to have it cleaned up at the machine shop and checked out with the heads getting a full rebuild and once over. I'll be in the L9H for about 5k when all is said and done, but as the dyno sheet shows that I attached in your other thread, its good for about 550hp and 505ft-lbs of torque, with more than 400ft-lbs being made everywhere from 2k RPM up. Tuning for the E38 is just the standard 2 credits on HP tuners.

 

[Craig Nedrow]

I have the combo in our 2018 GMC, great combo, hwy steady 13.5 towing around 8-9.5 mpg. Also have a lq4 W/ 4l80e, 115000 miles, runs good 1500 in Portland Or. my 454 with a 4l80e is a great combo as well, $3000 bucks. My other 4l80e trans from a box van, 500 bucks Seattle area. I think you are paying way to much.