1991 Burban V2500 6.2L Diesel

[Irish_Alley]

that ecm is only going to power the transmission, you wont have any worries about the ecm and engine like you did before. on top of all that the 4L80e is going to be a lot stronger and more reliable OD trans in my opinion. that being said if you want to swap out the trans youre going to need to find one with an electric speed sensor or your speedo wont work right. the transfer case you have now will be a 32 spline and its the only OD trans thats a 32 spline besides a later model manual trans. the 700r4/4l60 will be 27 splines. you might be able to find a 700r4 and transfer case out of 89??? (cant remember what year they started the electric speedo), but then you need a new front and rear driveshaft unless you find that setup in a burb. im going to add one last thing, i have that setup in my 91 v3500 crew cab with a cummins in front of it, and i abuse it. i did away with the ecm as the cummins was a first gen and i didnt have the right sensors to run the stock ECM. the "black box" i installed lets me manually shift the 4l80e at the cost of full line pressure. so this trans is really getting abused and used.

[fitz]

Your 87 suburban had an ECM unless someone removed it.
The 6.2 in your truck is a mechanical engine. All it needs is 12v to the injector pump to be happy.
Irish covered the 6.2/4L80 computer set up, I wont beat a dead horse. I will say I'd if you remove that 4L80 set up from your truck, sell it on Ebay. Lots of guys want that set up.

[Irish_Alley]

i know i would want it even if it just sat in the car port with my other cummins engine lol

[Deercreekfarm]

Thanks for the feedback. Let me weigh my options here and come up with a plan.

[ehjorten]

4L80e is pretty much bullet-proof!  I would keep it.  Plus you have overdrive which is key for these old trucks in making them much more enjoyable to drive!

[JohnnyPopper]

I feel your pain DeerCreeker!

Since it's been verified that a 700R came stock, I would go in that direction.

As far as the electronic control of that trans, there are aftermarket parts that accomplish that, and best of all, you control it.

The bonus of an overdrive is what I would find most interesting.

[Deercreekfarm]

Here’s a pic of the suburban. I removed the step rails / nerf bars and replaced the front bumper with a stock bumper. Have 3 or the original hub caps, just missing a front one.

I got it at what I thought was a great deal for a rust free 3/4 ton, diesel with barn doors (what I’ve always called m unicorn burban). I’ve owned a 1990 3/4 ton with barn doors but with a gas engine. An 1987 Diesel 1/2 ton with a tailgate but always wanted a 3/4 ton, diesel with barn doors.

As mentioned in another post I got the over heating problem worked out with new radiator, thermostat, water pump, fan clutch and new head gaskets. When I bought the truck the guy said it needed tranny work. The only problem with it is the OD is not working. Any ideas or am I looking at a tranny rebuild? She drives great and runs smooth just no OD.

Let’s see if I can get the tranny figured out then it’s on to some 1 ton or 5/4 ton axles, lift, wheels and tires then to the paint shop and onto the interior.

[Deercreekfarm]

Here is a pic of my old 1987 with a 6” lift running 36’s

[Deercreekfarm]

Here’s a pic of the 2003 3/4 ton barn doors gas engine I had gotten for my son.

[Deercreekfarm]

Question on the 4L80E no overdrive;

So as I mentioned the tranny has no OD. Called around and all the shops want to do a total rebuild and the cheapest quote I got was $1,200.

I found a married 6.2 engine J code in front of a HD TH400 Turbo with an NP208 out of a military CUCV in good running order all 3 for less than a rebuild on the 4L80E. I know the 400 doesn’t have OD either. It is the HD military version and I would have a spare J code NP208 (off my 91) and I guess my 4L80E.

Here are my questions;

How hard would it be to swap to the 400?

What would I need to do the swap?

Would it be better to rebuild the 4L80E?

[JohnnyPopper]

Better to rebuild the stock trans and keep the OD (that you don't enjoy now)

I'm not familiar with that trans- is the OD controlled by a processor? If so, have you checked out that angle? Is it as simple as 12v going to a valve/servo?

[Deercreekfarm]

Thanks for the input JonnyPopper. I may just go ahead and do the rebuild on the 4L80E like you suggested. Wife would be pooping kittens if I brought another engine, trans and t-case onto the farm.

[75gmck25]

Adding a 4L80E to an older truck is a common conversion, and there are quite a few articles out there about the conversion.  I assume in '91 it was controlled by the computer, but in many conversions they use an add-on controller.    I would read through a few of the conversion articles to figure out how the overdrive should be controlled, and you may find a simple fix to get it working.

Bruce

[Irish_Alley]

91 is computer controlled for the trans but the engine is another issue. its been a few years but i know gm used basically a tcm that was pretty much a standalone computer as it would only receive signal from a few sensors on the engine as the 6.2 and think the 1992 6.5 didnt need a computer to run.

[Deercreekfarm]

Adding a 4L80E to an older truck is a common conversion, and there are quite a few articles out there about the conversion.  I assume in '91 it was controlled by the computer, but in many conversions they use an add-on controller.    I would read through a few of the conversion articles to figure out how the overdrive should be controlled, and you may find a simple fix to get it working.

Bruce

Yeah it already has the 4L80E in it and I was considering stepping back down to a TH 400 Turbo but think I’m just going to rebuild the 4L80E