had a buddy hook this truck up to his snap on diagnostic computer to try and figure out the problem and this is what its doing, reverse worls fine, when placed into drive, the transmission starts out in second gear(you can tell and the computer also verified that it was starting out in second, regardless of speed, it will not shift out of second into third... when placed into manual 1st, it starts out in 1st, then you can manually shift into second, but again regardless of speed,( i took it to 55) it will not shift out of second into third. he asssumed it may be in limp mode but i know pulling the fuse for the tranny will put it in limp mode so i did that to check and the transmission acted totally different , it was taking off in third gear then. put fuse back in and it went back to what it was doing before... this is a rebuilt transmission by a pretty reputable guy around here so im having a hard time doubting his work, however, is it possible that the wires in the pan that go to the solenoids where crossed and hooked up to the wrong solenoids? any help is greatly appreciated

 

No warranty from the reputable guy?

 

Any codes?

 

Well the guy gave me a 120 day warranty on it butfor
some reason or another, I had speedometer problems as Soon as I put the trans in, turned out to be a bad conection where my gauge cluster plugged in, we found that our after the warranty had already expired. I will have to get the truck hooked back up to that computer to see what codes were thrown and il post back tomorrow hopefully

 

Just got off te phone with the guy that hooked it up to the computer for me and he said it didn't have any trouble codes at all

 

No, it would have had this problem when you drove it home from the trans shop if the wires where crossed up. It would have done this on the first drive.

 

That's the thing, this is the " first drive". I bought the transmission as a core, took it to the builder, then took it home and put it in the truck....

 

That's an important piece of information.


Old trans worked fine but wore out, new trans doesn't work fine. No changes except for the transmission?

It's in the transmission.

 

Looks like a year long problem, interesting stuff. Good luck.

Posted a year ago VVVV

 

i have since then replaced every bit of wiring in the truck and the problem before was with a different transmission that i junked, turns out that transmission was a 95' model with the PWM type pump. This transmission is definatley not PWM

 

Whats the 4 letter code on the PROM?
It's possible you have the right serv# with the PROM for a different application.

 

PROM? im not sure what that is.. also, the problem doesnt change when i switch the computers out

 

Theres a plate on the PCM held on with two screws. Take that off and you see the PROM, it has a blue plastic cover on it. The chip is in this part.

The code is removed from this one.

 

Serv.# 16168626
prom# in one computer is" 4298 BHAR"
On second computer that I have for the truck, the prom # is "BCFZ 1808"

 

The numbers I gave you were the numers on the blue plastic covers . There are two sets of 4 digit delco #s on a silver sticker inside that read "4895,3177" on the first one, th second is hard to read but I believe they are "1478,3056"

 

I can't find anything on the BHAR.
The BCFZ is for a 4.3 liter with a 4L60E, it goes with the service number of the pcm.

So I guess it's back to the wiring and transmission.

 

Oubt it matters but the truck has a 5.7....could a bad or missing ground cause this?

 

, is there anyway you could tell me which PROM #s will work for my truck? Because apparently I've got the wrong one

 

I can't find it. I have a 1992 3500 with a big block and have had my own list for a while. There are links all over the internet but not many people are burning chips for these trucks these days. There are reference sites like diy-efi.org but it's hard to find the list of BIN files. I have seen one before.
And another problem is, even if you bought a new pcm they expect you to use your old PROM.

If I were you, and I've done this myself, I'd find a pick your part junkyard and pull the pcm out of a truck of the same year with the same engine and transmission, and the same service number. The pinouts are not the same between certain different pcm service numbers. This could be the problem when you pulled a wiring harness out of a different truck, you might have the right pcm for your truck with the wiring harness thats pinned different.

Reading the 30+ posts you've put up in the past year about this same problem, I'd start with another wiring harness with it's matching pcm out of a truck exactly like yours.

I've learned that you can't trust organized, paranoid warehoused auto salvage companies, they'll hand you whatever they can get to easiest and argue with you that it will work. It's best to pull your own stuff.

 

Thanks for all your input, it's greatly appreciated.. I pulled the wiring harness tata in the truck now out of a truck in a junkyard, I believe the truck was a 94 gmc 1/2 ton 4x4 with the same engine, is it still possible that the wiring harness is pinned differently? At this point I'm loading te truck up and taking it to a transmission shop that said " they could diagnose it for free" ad going from there