A4 downshift double surge???
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From: Commerce Twp, MI
A4 downshift double surge??? Has anyone ever experienced this? When I'm cruising along at 65~70mph and floor it, the trans jumps into 2nd for the last few rpms of that gear. It kicks/jumps like any other downshift. But, after about .5 seconds it kicks again like it disengages and re-engages the drivetrain briefly. One of my logs shows the downshift where the VSS is at 68mph and the initial kick is pushing the car to 72mph. Then the car accelerates to 75mph just before it feels like something disengages. The VSS drops to 73mph during this second kick. When it feels like power is fully restored to the drivetrain (like the original downshift kick), the car takes off for the remainder of 2nd gear. It's hard to tell if this is spark related, torque management/abuse mode related, TCC related, etc. Are there any parameters/tables that would cause this either in the engine or trans settings? I would like to get a grip on this before I start tweaking the trans settings too much.
Last edited by SSpdDmon; Jun 22, 2005 at 08:31 AM.
Teching In
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I have had the same problem you explained,I was told that a combonation of things causing the problem.One is the sun shell has excessive wear and is not alowing the power to be sent thru the drive line.Two your clutch plates are probably worn and slipping during second gear down shift.I had my tranny rebuilt and the problem is gone,I had many parts broken the stock 4 pinion planetary gear set shattered,band and drum had 1/4 wide grooves cut into it.I had it rebuilt by a local guy here in Dallas Tx. with every upgraded to performance parts for 750.00 carry in only he does not install or remove the tranny. Hope this helps Robby
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From: Commerce Twp, MI
Originally Posted by dvanorder
What's changed? You mention wanting to get it fixed before tweaking the trans too much--have you made any adjustments to the A4 tables?
The only other tuning changes I've made were to the:
FANS (-16* out of on/off and run-on temps)
LTFT boundaries (0-1500, 1500-2500, 2500-4000, 4000+)
SPEEDO (adjusted for difference b/w stock 245/50/16's and current 275/40/17's).
Regardless of the changes made, this problem occured with the stock tune as well. It's hard for me to believe my tranny is going. The car just turned 30K miles and only 10K of them were mine. I bought it un-modified and it shifts strong in pretty much every situation except the one I described.
Red...I'll grab a screen shot of the info your talking about when I get home. No converter though. Just the mods in my sig.
Staging Lane
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Go ahead and post screen shots of those tables--sounds like they are going to be stock. I'm assuming the F bodies are like Y and there's no TCC at all until 3rd gear. It does sound mechanical, can't imagine it being TCC doing lock/unlock.
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