Can one fluid grind more than others?

**timberman00** · 06-18-2006, 05:58 AM

The 4.10's were installed last Tuesday. I put about 150 easy miles on them, and the M6 seemed to have smoother, quieter and quicker shifts. On Thursday, I changed the tranny fluid to RP Synchromax. I don't know what was in it before. Friday, I was cruising around, on/off highway, changing speeds, working in the new gears when 5th gear started to grind going in, then I had one HELL of a time getting out of 5th. Finally after a stop and go, 5th released. 1st through 4th are OK, but 5th and 6th ground.

Yesterday, I changed to DEXTRON III. Drove it less than a mile around the block. 1st through 4th are OK, 5th grinds a little less, 6th grinds alot less. On the 6-5 downshift, 5th grinds and grinds will not go in, I don't force it. 6-4 downshifts normally.

Oh, one more thing I noticed, when in 5th, the stick moves back as if it is trying to pop out of gear under slight acceleration. It does not pop out, it just moves back some. The stick then moves forward when I decelerate. The other gears seem normal.

Could changing lubes cause this? Or did it hasten a pending failure?

A friend told me to drive at highway speeds, then change fluids again. If this doesn't fix it, then he knows a good perfomance rebuild shop.

**INMY01TA** · 06-18-2006, 07:59 AM

From what I understand you dont wanna use syn. fluid in a pre 01-02 T56.

**Omega9** · 06-20-2006, 08:34 AM

Royal Purple synthetic is working great with my newly installed 4.10 gears. No problem at all, but my car is a 01.

**timberman00** · 06-20-2006, 10:29 AM

The Dutch have a saying that goes something like: Old too soon and too late schmart. I guess I got smart about a week too late. I'm still running the M6 on Dextron 3, and it's still grinding in 5th & 6th. But I only have about 10 miles on the new fluid change...