My 1990 Chevy K1500

[vargsmetal]

This will be the build thread for our overlander. I got the truck a couple years ago from a friend that managed to crash it into a parked car. The fender, bumper, and core support were pretzeled and he sheared the tierod. I picked up a cheap parts truck for those things did some maintenance items like the rear brake line, brakes all around, ball joints, etc... For tires I started with stock size 265/75R16 Cooper AT3. The truck had a TBI 5.7, 700R4, NP241 and having rpo code F44 it came from the factory with the 14 bolt semi-float rear axle.

We drove it in this configuration for quite awhile racking up 30k as my daily driver and we went on some trips to New Hampshire and Maine. Only real failure we encountered was mainly driver error using too much throttle in a mud hole in Maine. I grenaded one of the original CV axles, and damaged the other. We pulled both axles out, disassembled them and drove home to CT with just the stubs holding the unit bearings together.

With new CV axles and unit bearings we went on Northeast Overland's 2018 Fall Foilage tour and had an absolute blast. We learned a ton about picking the correct line and using the trucks wheelbase to get over obstacles. Ground clearance was always a problem but it made it through the trip with no issues.

Sent from my SM-G965U using Tapatalk

 

[vargsmetal]

After FFT 2018 I upgraded to 285/75R16 Cooper STT pros. This took some trimming of the bumper and the back lip of the fender. With the new tires I went on Northeast Adventure Company's Turkey Trek which was a day trip in NH. The trails were super rocky creek beds and they pushed the limits of the basically stock truck. I ended up with some extra character to the rockers, and one of the bed sides. The torsion bar crossmember has a nice wrinkle in it as well.

The water crossings were epic, and amazingly the only electrical issue I had was the wipers would stick on for a few minutes after each dunking. The major wake up call this trip gave me was the 700R4 overheated. It barely would shift out of 2nd and I lost OD completely. After it cooled down it worked ok and I drove it until this past December. The automatic transmission is definitely the weakest part of any 88-07 half ton chevy. 2008 and up you can get the 6L80 with the 5.3 in a 1500 which is a much better trans than the 700R4 or 4L60e. While I give the old trans props that I was able to finish the trip and drive it home, it needed to be upgraded.

Sent from my SM-G965U using Tapatalk

 

[vargsmetal]

That brings us up to the "build".

I really didnt have any problem with the TBI 350. It had plenty of power to spin the 285 mud tires with the 3.73s, and it got great gas mileage. With the 265s I was able to get a consistent 18mpg doing 75. It dropped some with the 285s but I never corrected the speedo so I never got an accurate mileage on them. The engine did have 172k on it, and it had the classic sbc piston slap at start up when it was cold out.

The 700R4 was the problem. It leaked from every seal and needed to be rebuilt after I overheated it. I could have got it rebuilt, installed a cooler and a temp guage and moved on but I wanted to upgrade. For 93+ trucks it's easier since they came with the electronically controlled 4L60e or 4L80e. All of the wiring is there and the computers can be swapped to control whichever trans you want to run. For my 90 I would've had to swap the computer and the complete engine harness to upgrade to the 4L80e and keep the 350. The other option was an expensive standalone computer for just the 4L80e. Theres also drive shaft issues. The 4L80e is longer so I would've needed a rear driveshaft from a 2500 and a custom front driveshaft. With all this I decided if I was going to go through the work of the transmission swap I wanted a fresh engine too.

I already had a complete 2000 5.3 cleaned up and ready to go for another project so I decided to go that route. The benefit here, besides an extra 100hp, modern sequential EFI, and tons of aftermarket support, is that sliding engine mounts are available. That allows me to place the engine farther forward in the bay so I can use stock driveshafts. I also had a core 4L80e I was going to rebuild myself, but I found out the bellhousing was cracked when I was moving it to the bench. I was out of time to mess around so I ordered a remanufactured unit from rockauto.

To bolt the original NP241 up to the 4L80e I had to swap the input shaft from 27 to 32 spline. I did a basic rebuild at the same time.

A huge part of this project is the wiring. I went through the stock 5.3 harness to make the changes necessary to run the 4L80e, and I removed the evap, egr, AC and rear O2 connectors. I used LT1swap.com for all of the wiring info and I also sent him the PCM to get the security functions disabled, emissions removed, 4L80e programming, and setup for standalone operation.

Normally people mate the original TBI harness in with the new engine harness but I wanted my setup to be cleaner than that. The TBI harness enters the cab at both sides of the firewall and uses tons of fusible links. I want all of my wiring on the drivers side and I'm going to use MIDI fuses instead of the links.

Sent from my SM-G965U using Tapatalk

 

[lilkia]

I thought it relevant.

 

[vargsmetal]

There's nothing wrong with the 4L60e, I just wanted the heavier duty trans. If this truck was just a daily driver I would've happily put another 700R4 in it. Ideally, I would've started this build with a 8 lug 2500, because that's what this will turn into anyway. Plan for next winter is to put a AAM 10.5 axle in the back and do a solid front axle conversion. I haven't decided on the front axle but the Chevy dana 60 is top of the list. I'll keeping the lift as low as possible and running 35-37in tires.

Sent from my SM-G965U using Tapatalk

 

[Buddha.]

After that many miles the stock in-radiator trans cooler probably isn't/wasn't doing much for you. On my '02 chevy I installed a trans temp gauge, I was seeing 220F in city traffic, unloaded on a 75F day. If I had tried to tow like that I would have burned the trans right out of it.

Interested in how you think the power compares to the 5.7.

 

[vargsmetal]

After that many miles the stock in-radiator trans cooler probably isn't/wasn't doing much for you. On my '02 chevy I installed a trans temp gauge, I was seeing 220F in city traffic, unloaded on a 75F day. If I had tried to tow like that I would have burned the trans right out of it.

Interested in how you think the power compares to the 5.7.

Yes, and it had the original radiator. I'm upgrading to the 34in radiator and adding a 40k Trucool trans cooler with a temp guage.

Sent from my SM-G965U using Tapatalk

 

[lilkia]

There's nothing wrong with the 4L60e, I just wanted the heavier duty trans. If this truck was just a daily driver I would've happily put another 700R4 in it. Ideally, I would've started this build with a 8 lug 2500, because that's what this will turn into anyway. Plan for next winter is to put a AAM 10.5 axle in the back and do a solid front axle conversion. I haven't decided on the front axle but the Chevy dana 60 is top of the list. I'll keeping the lift as low as possible and running 35-37in tires.
Sent from my SM-G965U using Tapatalk

I understand if I had a project like that I wouldnt even consider a 4l60. Theyre fine for a grocery getter, maybe a fire road blaster or even a peformance car thats going to see brief high power demands. If its going to see any kind of real offroad, or towing its got to be a th400, 4l80-5e, or allison. I wouldnt even go with the newer 6lxx theyre just as piss poor under heavy loads as the 4l60 or 700rs.

 

[Buddha.]

I understand if I had a project like that I wouldnt even consider a 4l60. Theyre fine for a grocery getter, maybe a fire road blaster or even a peformance car thats going to see brief high power demands. If its going to see any kind of real offroad, or towing its got to be a th400, 4l80-5e, or allison. I wouldnt even go with the newer 6lxx theyre just as piss poor under heavy loads as the 4l60 or 700rs.

I towed all over Colorado this summer pulling 10,000lbs. I was going just fast enough on the grades to pass semi trucks. My trans temp never went over 185F. How is the 6lXX piss poor?

 

[vargsmetal]

The 6L80/6L90 are solid transmissions. The 4L60e is solid too if used within its limits. It's all about keeping them cool and not driving like it's a medium duty. This thread isn't really about bashing transmissions. I chose the 4L80e because it's the economical option that's correct for what I'm doing with the truck.

Sent from my SM-G965U using Tapatalk

 

[Watt maker]

Interested to see where this build goes. I had a '92 Z71 extended cab years ago that I loved. It had a 350 with the TBI but I added a ProCharger on it and it would scoot. Mine had the 5-speed manual so I didn't worry too much about the transmission. I always wanted to LS swap it but sold it before I had the chance to.

 

[chilliwak]

Good looking truck you have there Mr Varg. Interesting that you went with a 4l80e. In my 94 Yukon with the 4l80e i will probably go with a complete complete computer delete and a manual push button overdrive with shift kit. I just hate the idea of having a computer in my truck. I guess I am just totally old school. Anyways thanks for posting pics of your build and welcome to the site. We all look forward to seeing what you do with you rig so keep us updated with lots of pics. Cheers, chilli...

 

[vargsmetal]

Good looking truck you have there Mr Varg. Interesting that you went with a 4l80e. In my 94 Yukon with the 4l80e i will probably go with a complete complete computer delete and a manual push button overdrive with shift kit. I just hate the idea of having a computer in my truck. I guess I am just totally old school. Anyways thanks for posting pics of your build and welcome to the site. We all look forward to seeing what you do with you rig so keep us updated with lots of pics. Cheers, chilli...

I can't really disagree with you. If everything I owned could be a mechanical pumped diesel with a 5spd manual I'd be a happy man. But on the other hand I'm good with wiring and electronics so I don't have a problem running a modern EFI engine and electronic trans, especially with this build because I can control how it goes together and make it easy to work on for me.

Sent from my SM-G965U using Tapatalk

 

[vargsmetal]

Haven't made much progress on the truck because I was fighting with AN fuel hoses. The first batch of fittings and hose I got from siliconintakes.com turned out to be an immense pain to assemble. After fighting with the first one for way too long I decided to go a different route. I ended up going with Earl's Vapor guard fittings/hose and they go together very easily.

The vapor guard hose isnt as rugged becuase it does not have steel braid over it but I've only got short runs to make at the tank and at the engine for flex. The bulk of the fuel line is steel tubing running down the frame. I'm going to use the same stuff for the transmission cooler hoses at the trans connecting to hard line up the frame to the radiator and cooler.

We did get the core support back on and I was able to test fit the radiator and cooling fans. The rad is a stock 34in for this body style; it would've came in a big block or diesel suburban or 3/4-1 ton truck. The fans are for a 2011ish F150 and fit the rad very well. I'll need to make some brackets to secure everything top and bottom but itll go together nicely. The power steering lines will need to be tweaked a bit so they're not rubbing against the fans.

Sent from my SM-G965U using Tapatalk

 

[Buddha.]

Fans look like they were made for that rad.