The infamous obd1/high stall converter problem

big dave · 12-19-2001, 07:07 PM

If anyone on this board would have a solution to this problem, you guys will. Apparently there is a problem with the obd1 cars (94-94 fbodys) having a converter higher than 2800 stall speed. I was somehow hoping that this wouldn't affect me so while my tranny was out for repair, I decided to have my stall speed raised to 3200. I guess I wasn't immune. At the track, if the car hooked, the tranny wouldn't shift from 1-2. Then it would go into some kind of a limp home mode where the overdrive wouldn't work until the car was restarted. After sending the computer out to Ed Wright for reprogramming and having that not fix the problem, decided to have the converter destalled back to the original 2800 stall speed. Have you guys dealt with this problem and what do you think it is and what do you think might be a possible solution?

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94 Z28 auto.White with white wheels.A few mods. 12.13@113 N/A with a 1.71 60'on nittos

96 Comp T/A · 12-19-2001, 07:25 PM

Convert to an OBD2 PCM. This is a proven remedy. Look it up in the LT1edit archives from about 2 months ago. A lot of people tried a bunch of different things and this is what fixed it.

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96 Comp T/A #84 of 172
LS1 brakes, LT1_edit for OBDII.
TNT plate kit, a4 to M6 in progress!!!, Hooker LT's !anything not serving a go-fast purpose.

89ProchargedROC · 12-20-2001, 02:45 AM

i've never had a problem with people with cars around me

we dont even use the computer to supply the line pressure anymore, we use a transgo vacuum modulator kit and dont have problems

its better off for the tranny in the end too and less troublesome than converting to OBDII

Kraest · 12-20-2001, 09:33 AM

Quote:

Originally posted by 89ProchargedROC:
i've never had a problem with people with cars around me

we dont even use the computer to supply the line pressure anymore, we use a transgo vacuum modulator kit and dont have problems

its better off for the tranny in the end too and less troublesome than converting to OBDII

Do you have to shift it yourself? I was running a similar setup, but had to shift it myself.

Some of the bracket racers (the only reason to even THINK about going with an automatic, IMO) didn't want to shift it, so they did the OBDII.

Mike

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1994 Sunset Orange Metallic Camaro Z28 Convertible - The Gorgeous and Sadistic Bitch Who Mistreats You and Lets You Down, Yet You Still Keep Her

1989 Red Ford Mustang LX 5.0 Convertible - The Dependable Girl Who Treats You Right, Yet Your Mind Wanders Elsewhere

kevkop94TA · 12-20-2001, 12:21 PM

big dave- You told Ed that the stall was a 3200? I'm surprised cause what I heard on this board was that he could fix it by adjusting the trannt tables. I'm a little worried now as I planned on 3500 stall with my heads/cam.

big dave · 12-20-2001, 12:26 PM

Yes, I did tell him it was a 3200. Apparently he redid the programming to change the gears by reading rpms instead of reading speed. It has something to do with the vss. Another interesting note was when I was going to get the obd2 computer from him, I was told that I would have to not only change the knock sensor but also a couple other things. Apparently with the 95 computers, it is far easier to do the conversion. I always thought the 94s and 95s were the same but apparently not.

big dave · 12-20-2001, 12:29 PM

KRAEST, now I didn't have to shift it by myself. It wouldn't allow me to do that. When I attempted manual shifts the same problem occurred.

89ProchargedROC · 12-20-2001, 06:24 PM

Quote:

Originally posted by Kraest:

Do you have to shift it yourself? I was running a similar setup, but had to shift it myself.

Some of the bracket racers (the only reason to even THINK about going with an automatic, IMO) didn't want to shift it, so they did the OBDII.

Mike

No, you dont have to shift it yourself. The stock OBD I computer STILL shifts the transmission at whatever rpm it is programmed at

BUT

line pressure is now controlled by a vacuum modulator reading TRUE ENGINE VACUUM do give the proper line pressures.

Trans go sells the kits to convert to this style for about $110 from trans shops that are local to you and install isn't hard

a_z28_vance · 12-21-2001, 05:42 PM

Quote:

Originally posted by 89ProchargedROC:
No, you dont have to shift it yourself. The stock OBD I computer STILL shifts the transmission at whatever rpm it is programmed at

BUT

line pressure is now controlled by a vacuum modulator reading TRUE ENGINE VACUUM do give the proper line pressures.

Trans go sells the kits to convert to this style for about $110 from trans shops that are local to you and install isn't hard

Do you happen to have the part #?? What if you have a hotcam, will that effect the vacuum pressure much?? In my IROC, I had to install a vacuum canister for my brakes b/c of the cam.

Pro Stock John · 12-23-2001, 12:06 AM

I have read this before, and it makes no sense to me.

Also, Pureevil (pureevil79@aol.com), a moderators on this ubb, ran at least a 4000 stall in his 95 LT1 TA last year and had no problems.

Is it me or were most of the cars having problems using LT1 Edit?

ODDII is even more complicated IMHO.

John
11.1 na LS1

89ProchargedROC · 12-23-2001, 02:19 AM

Quote:

Originally posted by a_z28_vance:
Do you happen to have the part #?? What if you have a hotcam, will that effect the vacuum pressure much?? In my IROC, I had to install a vacuum canister for my brakes b/c of the cam.

doesn't matter what cam you run because in actuality, the lower the vacuum reading at idle the more line pressure there will be in the tranny anyway which is a GOOD thing

no i dont have a part #

call your local transshop

Z2FAST8 · 12-23-2001, 06:26 PM

When I hammer it from a slight roll it seems like the tranny is slipping. Then I let off the throttle and get back in it and its fine. Also the ABS light comes on and stays on till I turn off the car

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94 a4,3.23,K&Nfilter, 80 series Flowmaster, no cat, Jet 2 chip, Transgo shift kit, TT3000 w/2.5 str

87 GN ~106k
air bag pass side, pinion snubber, boxed trailing arms with polygraphite bushings, trans has Art Carr line pressure mods and shimmed servo, Precision 210/205 cam with new lifters, springs, and roller timing chain, and roller thrust button, blue top 36lb injectors, modified plenum, Red Armstrong ign wires, XP fuel pump, and 93 chip, K&N 12in intake breather, engine breathers (2), tiedown, alky injection

The only replacement for displacement is BOOST.

OneFlyn95z28 · 12-24-2001, 01:45 AM

PSJ if it were just LT1 Edit WHY would Ed Write be having the problem also

he Hex edits

OBD II is not as bad as many think and has some good advantages

Later

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89ProchargedROC · 12-24-2001, 02:36 AM

personally, i think you are all nutz

We never had a problem with trannies blowing up (high performance ones with big stalls) at my shop unless it made a lot of hp and it DIDN'T have the vacuum modulator

then YES

it would burn up in a few months or less

but with the modulator, we dont ever really have comebacks

a_z28_vance · 12-24-2001, 03:37 AM

Quote:

Originally posted by Z2FAST8:
When I hammer it from a slight roll it seems like the tranny is slipping. Then I let off the throttle and get back in it and its fine. Also the ABS light comes on and stays on till I turn off the car

That sounds exactly like my car last April. Eventually I lost OD, then D, followed by 2nd, and finally 1st. Turned out to be my TC and it had came apart and destroyed the tranny. Good thing the shop rebuilt it for free again b/c of their crappy TC.

PSJ, I have heard of a couple people NOT having problems with the 1-2 shift at WOT w/ a stall of 3200 or higher, but that has been few and far inbetween.