3t40 Rebuild

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ifixalot
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3t40 Rebuild

Postby ifixalot » Fri Jun 05, 2015 11:41 am

HPIM1066.JPG

HPIM1065.JPG

HPIM1064.JPG


I thought I'd start a new thread for the rebuild.
It seems the weak link with this trans is reverse.
My band and direct clutches look to have a lot of life left.
But when I got down to the low/reverse clutches they are really bad.
I'm surprised I had no slippage in low, just reverse. Low has a lower
ratio so I guess that helped keep it from slipping.



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3X00-Modified
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Re: 3t40 Rebuild

Postby 3X00-Modified » Fri Jun 05, 2015 1:44 pm

Correct me if I'm wrong but I didnt think there was a "reverse" specific clutch... just a band that would reverse the direction of the output rotation... I know it a 4t60e there is an Input pack, a 2nd clutch, a 3rd clutch and a 4th clutch... When in reverse the only clutch enabled is the input, it's using the same clutch as 1st gear would but the band being engaged is what causes the output to spin in reverse.

I haven't cracked open a 3t40 yet so I am unfamiliar with how they orientated clutches. I have the book though.



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ifixalot
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Re: 3t40 Rebuild

Postby ifixalot » Fri Jun 05, 2015 5:27 pm

It's not reverse specific.
Low/reverse is used in forward low as well as reverse.
There is also a pipe which is called the low/reverse pipe which directs
pressure to the low/reverse clutch pack.
In reverse, the low/reverse clutch pack is used along with the direct clutch pack.
The band in the transmission is used for second gear, I think.



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ifixalot
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Re: 3t40 Rebuild

Postby ifixalot » Fri Jun 26, 2015 11:27 am

So I finally finished up yesterday, the transmission shifts fine so I guess I done good.
I had an issue with the new seals in my kit, one was defective out of the bag.
Then the replacement they sent didn't match what I had but it turns out it was
in spec with GM's standards.
Then I discovered Raybestes only gave me 4 steels for one of my clutches but an extra
friction so I went over everything to make sure I didn't screw up and I didn't. So I re-used one of
my original steels.
From my pic at the beginning of this post, I believe the wavy plates cause excess wear
to the lo-reverse friction discs. You can see how the friction against the wavy is the worst and the center discs are thick but chipped. What happened is, with the friction material gone, the piston reached it's maximum travel and would
not compress the clutch with enough force for it to hold. I could see the marks from the return spring bottoming out.
I decided to eliminate one wavy and put a used steel in-between the wavy and the friction. This would make the pack too thick so I used a surface grinder to grind about .007 off each steel so the over all pack will be thin enough. Now my lo-reverse frictions are up against a flat steel plate instead of the high points of the wavy plate. I'll probably be worm food before it wears out again.
My other clutch packs looked great, very little wear but my seals were a bit stiff.
During this project, I found things that give me the impression somebody did this before. Some bolts/nuts tight as hell
and some loose as a goose. My axle bolts for example, passenger side needed heat to loosen but the driver's side was actually loose. Trans to engine bolts, some tight, some not so tight.
The trans pan on the JY trans was kind of rusty but mine is like new. I think this trans was repaired
but not completely rebuilt at some point.
I also replaced my oil pan gasket, rear main seal, wheel bearing hubs, POR-15'ed my frame and control arms.
I also have a used swaybar since mine was busted.
This mini van should be around for years to come.



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Rettax3
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Re: 3t40 Rebuild

Postby Rettax3 » Thu Jul 02, 2015 9:27 pm

Nice work. Glad you have it all together again. It is sad for me to think that vehicles like ours are considered so disposable that an undertaking like yours (impressive for sure) is considered so out-of-the-ordinary, with the thought of 'why didn't you just junk it and got something newer?' probably whispered by most people -those who will never understand why we do these things ourselves. Again, glad it is done. :good:


1989 Super Charged 3800 Series II (First)Six-Speed Conversion GTU
1990 Turbo 3.4 Five-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 Five-Speed Indy GTi (Rebuild Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 3400 Top-End Auto OD Z-26


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