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125C buildups and tech help

Trannyman95

Trannyman95

Transmission Expert
I have built plenty of these and they came in a lot of the mid 80s GM cars and were even used up to almost current date in a few of the smaller cars like the Cavilier and Sunfire. While they are very light, reliable, and inexpensive they also do not have overdrive which will hurt highway fuel economy. On the inside the appear pretty fragile but do handle their share of power. The most common problem on this transmission is the TCC solenoid failing which causes lockup to stick on once the transmission warms up. Unplugging the TCC plug on the trans case will be a quick fix to keep your car from dying while pulling up to a stop but replacing the solenoid is the correct fix as no TCC operation will cause the trans to run hot and hurt highway gas mileage.
 


I don't remember. We bought it new and had it in to the dealer 36 times for different issues. Two things that plagued me were the rough idle (2.8l) and a stumbling. I kept telling them that when I slowed down the car chugged like a manual would if you didn't push in the clutch. In 95 for the first time it actually died when I came to a stop. Took it to the Ford dealership a block away and they replaced the TCS.:rolleyes: No more problems with the chugging.
 


I've always said that if either the engine or tranny goes out of that car for whatever reason....it's getting a transplant of a whole different animal.
 
Reptile said:
I've always said that if either the engine or tranny goes out of that car for whatever reason....it's getting a transplant of a whole different animal.
Click to expand...

yesterday and today Al and I have been installing the 90 440t4 (from the rear of the 442, orig from a 90 toronado trofeo) into his 88 cuttlass Ciera with the 2.8/125

we may have to find an optical VSS sensor from an older 440t4 if the unit from the 125 isnt compatible, but al can drive it without a speedo till then.

we originally were gonna toss in the LN3 3800 with it till we found the PCM was fried thanks to rodents chewing on the rear harness and shorting out several leads.

it sux, the ciera would probably get better mpg witht he 3800/4spd vs the 2.8 batchfire/3spd

anything to keep the olds junk on the road :p
 
IM considering putting in a 125C into my TGP if the tranny blows. I have been hearing that the 125C, in non-computer controlled form, holds the power, and transfers it better than the 440T4. And since the TGP is mainly a track car until I get the body redone, I am not concerned about MPG.
 
I know these things are getting rare, but I did get a come back from one a few years back on a newer vehicle. It smoked the 2nd clutch within a couple hundred miles and I found the 1-2 accumulator piston worn to high hell. They have upgrades for this now, I missed it when i put it back together, but this is a something that defiently needs attention. It isn't related to killing the engine, I just thought it might give a little help to anyone running a 3speed Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts i think they have the info on the accumulator problem.
I didn't mean for this huge text to show up for the sonnax website. I just wanted to let you guys know where you could find some helpful info on tranny tips. Tell this site that sonnax owes them some bucks
 
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