I started up my motor and drove my rig for the first time yesterday

I fired up my motor for the first time this weekend in a jeep with a 6.0L and TH400

The motor runs strong, but the trans shifts feel "squishy" and lazy. It feels like it's robbing me of some serious power. I know 40" tires and 4.88's on the street won't be spactacular, but I was thoroughly unimpressed with the acceleration.

The vacuum modulator is plumbed from the intake manifold to the modulator on the trans. This is pulling vacuum from the same place as the brake booster.

I am considering moving to a full manual valve body to eliminate and/or isolate this problem.

Also there is an audible clicking sound while coasting in Drive.

Thoughts? Let me know what further info is needed to diagnose this issue.

Any thoughts on squishy power-robbing TH400's?

I'm running the -2 Transgo kit and a forward shift valve body. No kickdown cable.

 

I had a few feel this way, but oddly enough it just needed a little bit more fluid lol is the trans used? New? Stall?

 

The trans is (very) used. It's out of a 2WD Suburban. I rebuilt it so who knows if I missed something.

I'm thinking the fluid level may be a major contributor here. It was the first time I ever filled an auto and the first time the rig was ever driven so the odds are stacked up against me. I have roughly 10 quarts in there right now. I thinking I may be a quart and a half low.

 

Yea that will make a significant difference being low on fluid, but did you replace the vacuum modulator when you rebuilt? Maybe try an adjustable one

 

The vacuum modulator was replaced. It came with the rebuild kit.

I'm condisering a full manual valve body to eliminate some of these variables. That would at least isolate the problem to another part of the trans.

 

Good points. Also, take the vacuum line off and see if fluid comes out of the modulator, that is a clear indication that it is bad.

Jon
PSI