2-3 Shift flare up in a 904...

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Cuda340

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Hello,
I have a question on why my 904 flares up about 700-800 RPM when I shift at WOT. Here's the combo: Motor 511HP-340, 5,000 Stall Converter,
904 Trans with reverse manual VB (turbo action), all MP clutches and bands, Low gear set, 5.0 lever, and deep pan. I have a trans oil temp gauge in the car as well and even on the street with the 8-inch converter it hardly breaks 140 degrees, not enough heat? At normal driving it feels fine, but then again I have a 5,000 Stall conv. and the stall kind of hides the shift. I am not sure what other info you need to make a diagnosis. There is only 500 miles on the complete rebuild and it has done this from the begining. All clearences where set according to the turbo action instruction manual. The 1-2 shift will snap you head off...
Any Help???
Thanks,
Jeff
 
I bet the 5.0 lever is causing it. Im sure Chris will chime in.
 
I use a 5.0 lever and don't have this problem. I've also seen it in stock trannys. The problem is either an early band release. You may be bleeding off pressure on the front band apply servo. I've seen some with sand holes in the bore or even excessive wear in the servo bore. Other things could be a late high clutch apply. Reasons could be a loss of pressure in or to the front drum. One of the most common causes I've seen for this is a front clutch drum that has the inner piston seal groove cut too deep so the seal lip doesn't stick out from the hub. In other words it's not sealing to the front clutch piston. You can check this when you pull it back apart, take out the front clutch drum and remove the clutches and steels. Take the spring and retainer out (you need a compressor, don't just try to pop the snap ring out). When you pull the piston out run your fingers across the inner hub on the drum and see if you catch the seal lip. If not there's your problem.
 
Cuda340 said:
Hello,
I have a question on why my 904 flares up about 700-800 RPM when I shift at WOT. Here's the combo: Motor 511HP-340, 5,000 Stall Converter,
904 Trans with reverse manual VB (turbo action), all MP clutches and bands, Low gear set, 5.0 lever, and deep pan. I have a trans oil temp gauge in the car as well and even on the street with the 8-inch converter it hardly breaks 140 degrees, not enough heat? At normal driving it feels fine, but then again I have a 5,000 Stall conv. and the stall kind of hides the shift. I am not sure what other info you need to make a diagnosis. There is only 500 miles on the complete rebuild and it has done this from the begining. All clearences where set according to the turbo action instruction manual. The 1-2 shift will snap you head off...
Any Help???
Thanks,
Jeff
Click to expand...

Hi Jeff,

The 5.0 lever would cause shift overlap from 2-3, as the band is slower to release with the 5.0 lever. This isn't causing your flare up between 2-3 however, I'd still recommend the 4.2 or 3.8 lever. Also, I'd recommend upgrading to a valve-body that applies the low-reverse band in first.

Do you know if the transmission had an orifice plug installed into the front clutch feed hole? This hole is located in the case (see arrow in pic), and is commonly installed with some shift kits. The smaller the orifice hole, the slower 3rd gear comes on. If this orifice plug is in your transmission, you can either remove it completely, which will allow 3rd gear to come on sooner, or you can remove it and drill the orifice hole larger.

Hope this helps .. keep us posted! :salut:

3rd_feed_plug.jpg


3rd_feed_plug.jpg
 
Thanks for all of the info. At least it will point me in the right direction. I am not pulling the trans out for another few months but I will let you guys know what was wrong.
Thanks again,
Jeff
 
Chris,
can I check for that plug and/or remove it with the trans in the car?? Just take off the VB?? Could this be an easy fix??
Jeff
 
Cuda340 said:
Chris,
can I check for that plug and/or remove it with the trans in the car?? Just take off the VB?? Could this be an easy fix??
Jeff
Click to expand...

I'm not Chris but yes you can do that in the car by pulling the valve body. You can also check the front band servo and servo bore with the trans in the car. You'll need to back off the band adjustment and remove the band strut.
 
Guitar Jones said:
I'm not Chris but yes you can do that in the car by pulling the valve body. You can also check the front band servo and servo bore with the trans in the car. You'll need to back off the band adjustment and remove the band strut.
Click to expand...


Hey Hey, Jones or Chris, might this ALSO be my problem with my 904 not wanting to upshift into drive until 40-45 mph? I have that restrictor plug in mine because it came with the TCI kit and said to put it there. I have posted regarding my trans not wanting to upshift to drive. Any help would be GREATLY apreciated.
 
Kraby, the way you described yours was a late shift, not a flair between them. I'd certainly look at that though if I were you.
 
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