1991 Burban V2500 6.2L Diesel

[Deercreekfarm]

It’s been a while since I’ve posted but I have a new toy;

I bought a 1991 Suburban V2500 4X4 with a 6.2L Diesel with Barn Doors on the back. Everything is factory and I call it my unicorn find. Here’s my question, what all is needed to remove the Gen 1 EDM (PCM) from the truck?  I know I will need to ditch the 460LE transmission for an older non electronic TH350 or TH400.  Has or does anyone know what all I will need to change, swap, add and or delete to do this?

Thanks

[VileZambonie]

91 Suburban did not come with a 4L60E and why do you want to remove ECM?

[Deercreekfarm]

Well it might not have come with a 460LE but that’s what it’s got in it. I thought they come with 700r4’s and I want to get rid of the ECM and put everything back to mechanical. I’ve owned numerous 85-87 models and never had a problem. Had a 1990 with ECM and had nothing but problems the entire time I owned it. I found this one rust free not abused and owned by Duke Energy so it was well maintained and cared for close to the level as the government used CUCV’s. I’m no spring chicken so I would like to get this thing set up to last me the rest of my life.

So has anyone had experience doing this before? Just looking for a little guidance.

Thanks,

[fitz]

91 Suburban did not come with a 4L60E and why do you want to remove ECM?

What overdrive trans did they use in the 3/4 ton trucks in 1991?

[Deercreekfarm]

I thought they used TH700r4’s but it has a 4L60E in it.

I’m thinking get rid of the intake and replace it with an 85 or earlier and drop a 350Turbo in it and that should eliminate everything connected to the ECM, I think?

[fitz]

As far as I know the 6.2 never came with a turbo 350, so you would be on your own with the kick down linkage. 

[Deercreekfarm]

Well I’m not sure of anything that’s why I’m on here trying to get some answers but instead all I’m being told is what I don’t no which is admittedly nothing about how to even attempt this.

Just looking for any help, advice from someone who’s done this.

[fitz]

Any chance it's actually a 4L80 in your truck?

[Deercreekfarm]

Could be. I will have to crawl under it and look at the bolt pattern of the pan. When I bought it I was told it has the 4L60E in it. Knowing I want to ditch the ECM I wasn’t to worried about it because I figured it was coming out anyway.

It’s been years since I’ve messed with these trucks but if I remember correctly every trans from the TH350?to the 4L80E all have the same bolt pattern to mate up to the motor correct?

[fitz]

Yes.

[VileZambonie]

91 Suburban did not come with a 4L60E and why do you want to remove ECM?

What overdrive trans did they use in the 3/4 ton trucks in 1991?

700R4/4L60 or 4L80E

[Stewart G Griffin]

If it's a 3/4 ton, then i think a 4L80 E.

Does the computer/ECM even control anything on a 6.2 diesel?

[Deercreekfarm]

I crawled under it and it is a 4L80E transmission in it. The guy I bought it from obviously didn’t know what he was talking about.

My understanding is that the ECM controls throttle and shift points. Maybe someone anyone knows more than me and will chime in here.

As I mentioned before I want to delete the ECM and put everything back to mechanical. Just wanted to see if anyone had done that?

[Irish_Alley]

you need a computer to shift that trans, doesnt have to be the ecu but it needs something. you can get a standalone box for it but they do cost $500+. its been some time but i thought the ecm on those is pretty much a stand alone computer and only reads inputs from the tps and rpms. i picked one up (ecu and wire harness for a 6.2 and 4l80E) a few years ago but never got around to messing with it. so why do you want to get rid of that trans besides the bad luck in the past?

[Deercreekfarm]

I’ve had 85-87 year suburbans and the things last forever. I had a 90 suburban with the ECM and literally spent more time under the hood than behind the wheel and it always led back to the ECM. I found this 91 (last year of the square body) rust free, 4x4, 3/4 ton, diesel with barn doors and plan on keeping it but don’t want to fight with the stupid computer. I would like to delete it and do whatever it is I have to do to the engine and swap out the trans for an older mechanical model.