Tcc trouble (Page 2/2)
Gizmo0816 JUL 30, 08:41 PM
Could someone point me into the direction of a compatible torque converter for the th125c? I found one from rock auto, but i'm not sure it's correct and it's out of stock anyhow.

These are the two converters i've found that i think are compatible, " B21HZ2" and "B21FZPB". please correct me if I am wrong.

[This message has been edited by Gizmo0816 (edited 07-30-2025).]

Dennis LaGrua JUL 31, 09:11 AM

quote
Originally posted by Gizmo0816:

Could someone point me into the direction of a compatible torque converter for the th125c? I found one from rock auto, but i'm not sure it's correct and it's out of stock anyhow.

These are the two converters i've found that i think are compatible, " B21HZ2" and "B21FZPB". please correct me if I am wrong.




Don't have an exact part number to share but the TH125 transmission was used on dozens of GM car models of the 1980's and early 90's.
From wiki
1982–1996 A-body
1980–1985 X-body
1982–2001 J-body
1990-1993 W-body
1987–1996 L body
1990–1995 U-body vans (with LG6 engine)
1984-1988 Pontiac Fiero

While all these TC applications should bolt in, the difference would be the stall speed which is different from the 4 cyl and 6 cyl. applications. May have more info to share but it is at home. When I get back tomorrow will look it up but not sure that the TC is your problem.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Gizmo0816 JUL 31, 04:52 PM

quote
Originally posted by Dennis LaGrua:


While all these TC applications should bolt in, the difference would be the stall speed which is different from the 4 cyl and 6 cyl. applications. May have more info to share but it is at home. When I get back tomorrow will look it up but not sure that the TC is your problem.



Alright thanks for the information, and i would greatly appreciate to hear back when you get the time.

So the reason im thinking its the torque converter, which I'm not saying you are wrong as I don't know anything about the transmission apart from what its doing, but it shifts great, this transmission has given me less problems than the tranny in my 2012 corolla
Atf is cherry red, no burnt smell, I opened up the drain pan to see if there were metal shavings on the magnet and I discovered the magnet was missing, I put a new donut magnet back in, but that obviously means a previous owner dug around in there. However a few hundred miles later atf is still cherry red, still shifts really smooth. Just when the tc is supposed to disengage when lightly accelerating between 30 and 45 it's stuttering. Unplug the tc it goes away.

If there is something else that would cause this tho I am 100% willing to chase that down.

Oh yeah forgot to mention, I put 200 miles on her in one day one drive, no stops at all, just for the giggles to see if something would happen, it ran perfect the entire time. It was about an almost 4 hour drive.

[This message has been edited by Gizmo0816 (edited 07-31-2025).]

Dennis LaGrua JUL 31, 07:38 PM
1987 -1992 Chevolet Beretta Torque Converter should interchange with the Fiero unit. That would be part B21FZPB and its for the Iron Duke 4 Cyl

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 07-31-2025).]

Gizmo0816 JUL 31, 09:54 PM

quote
Originally posted by Dennis LaGrua:

1987 -1992 Chevolet Beretta Torque Converter should interchange with the Fiero unit. That would be part B21FZPB and its for the Iron Duke 4 Cyl



Thanks the b21fzpb was the one i was gonna go with, autozone said it was a direct fit, but its good to be certain.