The 125c KIT

[TurboGTU]

The instructions are straight forward. The tv cable should have no slack when the throttle is wide open. Other thing you can do is reuse your gov springs or just look for a quad 4 3t40 at the u-pull it and get the whole gov. Did you bend the tab at the bell crank?

[3400-95-Modified]

No the guy I know is running all Raybestos performance clutches, and I think his builder does some other things to it as well but I'm not sure. They are a pretty tough unit when built properly, but you can do the same with a 60e if you correct the flaws it has.

[16vconversion]

Yet I hear from the guys running a built TH125, that the 60e is a lost cause... LOL

What would be "Built" eagle clutches/steels redline oils ? . it's been going quite nicely with "the 125 Kit" crisp shifts but 2nd feels kinda short . and I need a new Lockup solinoid

[3400-95-Modified]

Not many people on here are running a TH125... Ask a question on a 4T60E and you'll get a lot better response. Not saying there aren't people on here that know about them, just not as many as I think you are hoping.

Yet I hear from the guys running a built TH125, that the 60e is a lost cause... LOL

[16vconversion]

exactly, the 125 is kind of a bastard child. It's rare to see anyone put any money into them.


From what i've seen over the years, the people who have just put in a kit reported mixed results. They probaby did it on trannies that were trashed to begin with. with a total rebuild they can be built rather strong but expect to spend 2-3K.

The trans only has 55k on it , I originally just wanted to do the lockup solenoid and be done with it , but for 34$ shipped I went with the kit. It fixed the trans slip on first start-up of the day ( converter was draining back in to the pan , fixed with a check valve in the upper trans cooler line) and made 3rd feel way firmer , now its not a tire chirping th250 but it definitely feels a lot tighter

[Superdave]

Not many people on here are running a TH125... Ask a question on a 4T60E and you'll get a lot better response. Not saying there aren't people on here that know about them, just not as many as I think you are hoping.

exactly, the 125 is kind of a bastard child. It's rare to see anyone put any money into them.


From what i've seen over the years, the people who have just put in a kit reported mixed results. They probaby did it on trannies that were trashed to begin with. with a total rebuild they can be built rather strong but expect to spend 2-3K.

[gpse3400]

If the TV cable is at the right adjustment, the only thing you could do is pull out on the cable itself some more(alittle hard to pull, listen for the clicks), which in turn would make the transmission shift even earlier; not what you want. You might want to check your governor again.

[bszopi]

I did the TV cable detent adjustment , seems it was adjusted properly. I thought this was the place for trans professionals ? . Anyone else install a shiftkit into a 125 ?

Not many people on here are running a TH125... Ask a question on a 4T60E and you'll get a lot better response. Not saying there aren't people on here that know about them, just not as many as I think you are hoping.

[Honest Don]

I would put the old governor spring back in and see what that does.


checking the TV cable again wouldn't hurt. With the throttle 100% open, the TV cable should be 100% pulled as well.

[16vconversion]

I did the TV cable detent adjustment , seems it was adjusted properly. I thought this was the place for trans professionals ? . Anyone else install a shiftkit into a 125 ?

[86FieroSEv6]

As far as I am aware of, GM used an auto adjust mechanism for the TV cable. You depress the ratchet lock and allow the cable to reset. Then you firmly plant the throttle on the floor and you should hear the adjuster ratchet into place. This is supposed to be the default adjustment. Of course, the best adjustment is with a line pressure gauge and the advice of a transmission expert.

[16vconversion]

Just got finished rebuilding my valve body and WOW ! , What a Job ! I drop the frame , drop the trans, pull steel Halo off , pull the cover and pull the valve body . !! I highly recommend to anyone who pulls the valve body to mess with it will need the separator plate gaskets Period ! !! I ground a pair of flats in the pressure regulator as per instructions , replaced a few springs a per also , and drilled the plate where indicated.
I also replaced the spring in the governor , not that bad 2 10mm's and a PITA getting the new spring in without disassembling the governor.
Dropped the pan and removed the servo cover and replaced the spring as per the instructions , removing the old accumulator and replacing it with the supplied "Ben Law" part. and replaced the lockup solenoid as well .

Okay , so now with the questions . can I adjust the tv cable tighter to move my shift points higher ? or should I put the old governor spring in ? has anyone ever had any experience with the 125 kit ?

Btw the trans is shifting fine but awfully quick. 3rd gear by 35mph medium throttle.

I think I need to pull the side cover again as the TCC has started acting up , staying engaged.