99TransAmK

I have a 99 Trans am with an automatic trans with 142,xxx miles on it

I am having an issue when shifting into D & R it shifts hard I have been trying to figure out the issue myself reading posts here and my knowledge as a mechanic but im running out of idea's and everything that I have replaced has been worn out.

I have replaced the motor and transmission mounts, both u-joints, maf sensor, map sensor, cleaned the throttle body, tps, torque rod bushing, reset the fuel trim and the fluid for the trans looks fine.

I was wondering if the new mounts could be to stiff and maybe need to be broken in I used oem style rubber bushings.

bbond105

Have you scanned the engine and trans for fault codes? Some stored codes will cause the PCM to rase the transmission line pressure which would cause the trans to slam into gear and harsh shifts. Scanning for codes would be the 1st place that I would look.

99TransAmK

I forgot to mention that there are no codes at all for the engine or transmission

bbond105

Are the u-joints tight? Is there excessive back lash in the diff?

You could put a pressure gauge on the trans and get a line pressure reading, this would help to pinpoint if the problem is in the trans or not.

FranksCustomTrans

Whats your engine idle speed ?

99TransAmK

The rpms were at 1k right after the start up then dropped down to the 827 and the 691 was after about 3 min of running

99TransAmK

When I first started the car up the idle went up to about 1k rpm then went down to 827 rpm and after about like 3 minutes its was at 691 rpm

FranksCustomTrans

Idle sounds about right, I would say get a pressure gauge on it and see what the line pressure at idle. Also check that your trans temp sensor is working as it varies line with temp.
Stiff mounts could be issues but cant say unable to feel them, GM mounts tend to be rather squishy even new,

99TransAmK

The pressure at idle is 60 PSI
reverse pressure is 90 PSI

also the fluid level is fine and the fluid is like a brown/red more of a red tint to it and doesn't smell burnt

bbond105

Pressures are normal.