Whats the differences in 3t40/125c transaxles???

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Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Fri Apr 10, 2015 4:38 pm

I have my 94 Lumina mini van. There is a vinyl bar-code sticker on the side/front that has a big 4 CRC on it.
It says made in USA. The paint is off the metal sticker by the shift lever so I can't read that.
I think I have a transaxle that is 2.84 final drive ratio.
The RPO sticker says my final drive should be 3.06. Makes me think my trans was replaced
at some point. I have a problem with this trans slipping only in reverse under load.
I see 89 Berettas have a 3.18 final drive, 92 Beretta has a 2.84.
Car-Part.com shows I can use Buick Century, Olds Ciera trans but they don't show Beretta's.
won't a Beretta 3t40 fit? Are the axles different??
I'm amazed that they show a trans from a 3000 pound car with a 4 cylinder engine
and I'm supposed to put that in a 3500 pound mini van with a v-6??
It makes me think I have one of those and that's why it slips in reverse.



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Re: Whats the differences in 3t40/125c transaxles???

Postby Asylum » Fri Apr 10, 2015 8:43 pm

They are all interchangeable. A 3t40 is a 3t40, period.

However there are probably a dozen or more different 3T40 combinations when FDR and converters are concerned.

From mild 2:76 to 3:73 FDR units were used in all sorts of applications.

If you need one decoded e-mail Jeff at http://www.engineered.net with the three letter code on the blue tab attached to the top of the transaxle.

The axles are also of myriad lengths, but you can use what you have, They are all interchangeable.

Converter wise hold on to your hat.

Here is the list of what GM used.

FA 2795 RPM stall
FB 2560
FC 2385
FD 2095
FE 1860
FF 1720
FG 1630
FH 1514
FJ 2061
FK 2760
FL 1897
FM 1525
FN 2538
FY 1420
FZ 2363

Now most of these are very specific for certain option combinations. The FA's and FK's being the most desirable for performance applications, but choose your poison.

They mainly were used in 4 cylinder applications.

FWIW


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Re: Whats the differences in 3t40/125c transaxles???

Postby 88*Beretta » Fri Apr 10, 2015 9:58 pm

Asylum wrote:They are all interchangeable. A 3t40 is a 3t40, period.


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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Sat Apr 11, 2015 9:39 am

Thanks to both you guys for helping out with very useful information.



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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Thu Apr 16, 2015 12:21 pm

I have a chance to buy a very low millage, 1987 th125c out of a Pontiac Fiero.
I'll use my torque convertor and swap the chain sprockets so I'll have the same
drive ratio I have now and I think I need to swap in my speed sensor.
I know GM did a TSB in early 90s about the reverse clutch pack adding a wavy plate or something.
But should work OK eh?



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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Wed May 27, 2015 11:18 am

Update
The guy with the above trans sold it to someone else the morning I was to pick it up.
Jeff at "engineered" didn't reply to my email questions.
I wasn't sure if my trans is original because it is just so clean inside.
I got a JY trans which was supposed to be good. They are supposed to take out the filter
so I'd have to put in a new one. They left the filter in, so I cut it apart to see how it looked inside.
HPIM1052.JPG

Those are flakes of what looks like friction discs. So much for getting a good trans from a jy.
So back it went but they then told me they have no other matches for me.
I think they just wanted more money. So then, I read a thermo element
can cause a reverse slip condition. The cure is an older style manual valve.
From the jy trans, I learned I can pull the manual valve
while the trans is in the vehicle.
I got one off Ebay. I go to put it in and I discover I already have an older one!!
So I'm thinking maybe I have an older, not original trans in my van.
I have the old style shift valve. Mine is made in USA and the one from the jy was made in Canada.
Thinking they moved production to Canada, again I thought my trans was older.
I need to know so I can order the right rebuild kit. I have the 96 Beretta service manual.
It says USA built 3t40 serial number starts with the two digit year, Canada has one digit for the year.
So mine has two digits so it looks like mine is a 1996 trans but it has been worked on because it
has the old style manual shift valve in it. I bought the ATSG books on my trans and they say two
other things can cause the slippage. Cracked direct drum and a bearing shifting and wearing through
the driven support hub. So now I plan on pulling the trans. On a Lumina van, they say you need to drop
the whole engine cradle. I'm going to see if I can get it out without dropping the whole cradle.
I will have to pull the axles. Is it faster to disconnect at the lower ball joint or disconnect the control arm?



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Re: Whats the differences in 3t40/125c transaxles???

Postby 3X00-Modified » Wed May 27, 2015 3:04 pm

a 1996 3t40... WHAT? A 96 Beretta only came with a 4t60e no questions asked so I don't know how your 96 manual states how a 3t40 code would be written.



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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Wed May 27, 2015 4:06 pm

Sorry, "94" transmission in my 94 Lumina mini van, I got info about the serial numbers and that fact
trans-axles were built in Canada and Michigan from the 96 Beretta service manual.
I don't know why 3t40 info is in the 96 service manual except maybe the 4 cyl came attached to a 3t40?
(page 7A-80) Anyway, I typo-ed 96 instead of 94.
This has been like solving a mystery and getting one clue at a time every few weeks.



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Re: Whats the differences in 3t40/125c transaxles???

Postby Cliff8928 » Thu May 28, 2015 3:45 am

Yes, the 2.2 did have the 3T40 as the sole automatic transmission.


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Re: Whats the differences in 3t40/125c transaxles???

Postby Rettax3 » Tue Jun 02, 2015 11:13 pm

Pop the ball-joints. It is a toss-up on ease between the joints and the arms (depending on what tools you have), but the arms are much more frustrating to realign than the ball-joints, IMO. At this point, you could probably teach a class on these trannys to most of us. :)

I would try supporting the engine from the top, dropping the subframe (as listed in the manual), then lower the engine at an angle (tranny-side down, obviously) and separate them to slide the tranny out. That is how I do the GTU's six-speed, it is the easiest way (and with that car -smaller bay than your Lumina, and longer engine and wider tranny too- it is the only way, other than dropping the whole drivetrain out) to separate them.

Good luck, you are due for some! :good:


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Re: Whats the differences in 3t40/125c transaxles???

Postby Cliff8928 » Wed Jun 03, 2015 2:43 am

I do the same. I have one of these to do the supporting and lowering...

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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Wed Jun 03, 2015 9:57 am

HPIM1055.JPG
I wish I had one of those to support the engine! I will probably make something with a 2x4.
I did that when I replaced the rusted engine cradle on out Saturn SW2.
On the Lumina van, the valve body cover stuck out too far.
I removed it and made a cover plate of wood to protect the mating surface.
I think with it removed, I have plenty of room to drop it out the bottom.



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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Wed Jun 03, 2015 1:24 pm

HPIM1057.JPG
Got the stabilizer bar off, uh oh I wonder if a weld would hold?
I never noticed any excessive sway but then it's a mini van I didn't expect
it to handle very well. When I bought it, the passenger side ball joint had been
replaced and I got the impression somebody hit a pothole so maybe it's been broke
all this time.



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Re: Whats the differences in 3t40/125c transaxles???

Postby 3X00-Modified » Wed Jun 03, 2015 1:39 pm

No you can not weld spring steel, or at least if you do it will break almost instantly at the same spot when torsion is put against the swaybar.



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Re: Whats the differences in 3t40/125c transaxles???

Postby ifixalot » Wed Jun 03, 2015 3:31 pm

Yeah, I agree, after posting that, I read up on the subject and I found a used one on Evilbay and ordered it.
$55 shipped.




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