th400 slow 2-3 shift - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-05-2003, 11:58 AM
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th400 slow 2-3 shift

I researched the archives and I learned a tremendous amount about GM transmissions (this is a GREAT forum!) but I still need some specific help on my shift problem.

I have been running a th400 on the street/strip for 3 years. It has seen very limited miles. It was overhauled (TCI)and shift-kitted before I installed it in the car. It has an auxillary cooler, deep pan, electric kickdown not attached and I use Mobil 1 transmission fluid which has been changed once and is very clean. I run a trans temperature guage and the trans has never been hot.

The trans performed flawlessly for three years then at the last 2 races this season, I began noticing a "lazy" 2-3 shift. The 1-2 shift is still solid and my ET's were not affected but I am sure it will not cure itself and will get worse unless I do something. Am I faced with another overhaul or is there something that I can try without overhaulling it?

Thanks for any suggestions.

John

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Old 11-06-2003, 05:59 PM
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th400-Any help out there?

No response to my 2-3 shift question so far. Do any transmission folks want to venture an opinion?
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Old 11-08-2003, 11:45 PM
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I will stick my neck out here. Not sure I will be any help but you could try dropping the VB and making sure your center support bolt, (the 3/8 12 point bolt under the VB) is tight. Then round up a couple of rubber backed steel cup plugs from a 200 trans, (the one that goes against the center support in a 200 to seal it) and drive them in the two feed passages, one on either side of that bolt. Those are the feeds for the hi clutch. Other than that, I haven't got any answers. If it was working good and now it isn't, the support may have shifted in the case to the point that flow is restricted. There is case savers to remedy this problem, but the unit needs to come out and apart.
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Old 11-09-2003, 08:40 AM
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Cool

A developing weak 2-3 shift can be many things. As mentioned the center support is the area of concern.

Loose fit in the case, sealing rings wear grooves into the drum area.

Mis-matching the center support is a probelm too. GM changed the width of the center support area that meets the case. They installed a .045 thick wear ring in there to help a problem of wear into the aluminum .

If this is wear ring is left OUT the support will move around and even break the support bolt that was mentioned above.

You do not mention if the direct clutch is dual feed or if a shift kit is installed

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Old 11-13-2003, 03:19 PM
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Thanks KRP and Crosley. Looks like I will take a peek under the VB and hope I find something obvious. Otherwise, I guess we'll tear it down.
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