I'm getting ready to swap my 125 for a 4T60. I got the tranny out of a '94 Grand Prix, but it's got the pulse type speedo sensor.
I just wanted to make sure of this: Can I swap the TH125 governor assy into the 4T60?? The output is the same (3.33).

I REALLY lucked out on the tranny - Free and only 72,000 original miles on it!!

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Mick
1986 GT

If you got a 4T60 it should have a throttle pressure cable and a vacume modulator. If it doesnt, it isn"t right. I thought they stopped making the 4T60's in 1990. You might check this out good before you remove the TH125.
Joe Crawford
Texas

Might be some confusion between a 4L60 and a 4T60.

[This message has been edited by PineyCreek (edited 02-24-2008).]

Nope, she's good. Vacuum modulator (big one), kickdown cable and all.

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Mick
1986 GT

Well.............
Can I swap the guts from the 125 to the 4T60??
Oops, looked back over the 1st post. It's a '92 model.

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Mick
1986 GT

[This message has been edited by cropduster (edited 02-28-2008).]

Yes, you can put all the guts in but you will probably need to change the cover. That is what I did. I went to the junk yard and got the correct style cover from an earlier year 4T60.

Great! That's what I wanted to hear.
Thanks!

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Mick
1986 GT

There's some info on that at the bottom of page 1 in my build thread - you will need a taller cap than the TH125c came with.

"There are 3 variations of speedometer assemblies that I have seen on 4T60 transmissions. One type is almost exactly the same as the one used on the TH125C transmission and will plug directly into the Fiero speedometer connector. A 2nd type is almost the same as the first except the speed sensor (item 1) has been replaced with an assembly that screws into a mechanical speedometer cable. This type can be used if reassembled with speedometer sensor from your old transmission. Both the mechanical cable and sensor type speedometer assemblies are held in place by a 1-inch wire clip on the top of the governor cover. NOTE: The TH125C governor cover (item 3) is NOT interchangeable with the 4T60.

A 3rd type is an electronic pulse generator assembly that looks quite different from the original TH125C governor speedometer sensor. The electrical connector and more importantly the signal generated by this unit are not compatible with the Fiero. If your transmission has one of these units the entire assembly must be replaced with one of the previously mentioned types."



Cheers,
Ryan

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1986 Fiero2m8 (LT1 NX / 4T60 Roadster Build)
https://www.fiero.nl/forum/Forum2/HTML/071642.html

Thanks for the info Ryan, so just to make sure......
I swap the gears from the top of the governors (keeping the 4T60 governor with the 4T60 tranny), and get another cap from a 4T60 that doesn't have the pulse type VSS right??

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Mick
1986 GT

Im in the middle of the swap to but am having a heck of a time trying to find the right cover for the 4t60. What years and models did you guys find them on?

Thanks,
Jason

Sorry, can't help you with which car the cover comes off of. I just went to the pick a part and looked at the gear shifts for 4 speeds and then crawled underneath to look for which governor it had. Didn't pay much attention to the car. Also, you might need a new electical plug. I had to splice in a round plug that matched the socket on the 4T60.

quote Originally posted by cropduster: Thanks for the info Ryan, so just to make sure...... I swap the gears from the top of the governors (keeping the 4T60 governor with the 4T60 tranny), and get another cap from a 4T60 that doesn't have the pulse type VSS right??

Correct.
The weights on the lower part of the shaft are matched to the final drive ratio, so best remove the pulse type from the top and install the Fiero style.

Look for a 440T4 trans 1987-89 range for the correct cap (taller version of the Fiero one).
Pulse types are easily spotted by the larger electrical plug vs. the 2 wire plug you need.
I got my 4T60 trans from a 1990 Cadilliac Deville/Seville and I think the cap was from something like a 1988 Buick Century or Electra.

Ryan

Are the weights what control the shift points? Mine seems to shift into 3 and 4 too soon.

Yes, they play a part along with the Throttle valve cable and the vacuum modulator.

Well, just got back from the boneyard and got the brackets I needed, but I couldn't find the governor cap.
I must have crawled under 30 cars too. I just kept finding either the pulse type, the version after that or the 125's.
I remember crawling under an 88 Century too.
I think it would be easier for me to find a place that already has the trannys out then see if they will let me buy the cap.

Edit: Just to make sure I ain't passing up the right one, what does the right cap look like for the 4T60??
All the pictures I see are of the 125, then the pulse type, the kind you DON'T want............

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Mick
1986 GT

[This message has been edited by cropduster (edited 03-01-2008).]

It looks just like the TH125 cap only it is taller and a little larger diameter. Seems like the bolt pattern is a little different as well. I can try to get a picture but it might be difficult to see on the car.

Cropduster- I know how you feel, Ive looked at easily 100 cars by now looking for that stupid cap.

Jason

Well, this is the best I can do for you. I pulled the cap off the 4T60 that is in the car. I don't have the TH125 cap anymore so the below pictures show the cap you want on the left and the pulse type that won't work on the right. BTW this is my first time posting picts so forgive me if it doesn't come out right.

Dang ahawkman!! I didn't mean for you to take yours apart!!
But thanks, that's what I wanted to know. So I really DIDN'T find the right one today.
The one I need looks almost identical to the 125 except the mounting holes. Too bad tomorrow is Sunday or I would have the last piece of my puzzle.

Thanks again!!

BTW, pictures are perfect!!

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Mick
1986 GT

Thats the first time Ive actually ever seen the right cover! Thanks!

Jason

No problem.

Finally found a cover yesterday at the yard! Came off of a 1985 Olds Cierra.

Jason

Finally!! Looked through the whole yard till I found my cover on the last row of cars.
It came off a '88 Pontiac something with a 3800 engine. The trick to quickly finding
the right one is the mounting bolts. The wrong one is held on with 10mm bolts,
the right one is held with 13mm bolts.
Now to get the top gear off. There isn't a clip holding it so I assume it's just pressed on??

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Mick
1986 GT

[This message has been edited by cropduster (edited 03-19-2008).]