Tomi72

Last weekend I swapped my new 400 cid engine in along with a rebuilt th400. The engine is running fine but the transmission is giving me a headache. It did work normally for about 30 miles but then it started to act funky.

With the gear selector in drive (with light throttle) it keeps the car in first gear until about 3500 rpm and then shifts directly to third. If I select L2 while the engine is revving high in first it will shift into 2nd gear, then when I put it in drive it will shift to 3rd but for a couple of second it feels like it's in neutral with engine revving freely. If I have the gear selector in L2 it doesn't always shift to first when slowing down, not even if I stop completely. Also the kickdown doesn't seem to work from 3rd to 2nd (I can hear the solenoid in the trans click when I press the accelerator pedal). When the trans is in gear it doesn't seem to slip abnormally, the fluid level is ok, so is the shifter cable adjustment.

Could the new engine that has lower manifold vacuum cause symptoms like this?? It did work ok initially so I doubt that is the problem.

If anybody has any ideas what could be wrong please let me know. The guy who rebuilt it is going to take a look at it next week, but I'd appreciate any ideas you guys have.

rgds Tomi

Missileman

Sounds like the modulator is not getting vacuum or has failed.

emsrescu

when you put it in r does it go right in or take a few seconds

Tomi72

The reverse goes in right away.

I checked the vacuum hose and it's ok, I'll try to check the modulator itself. Could lowish engine vacuum cause this (about 10")??

VETDRMS

At one point I had 6-8" of idle vacuum, and I had no problems with shifting. It sounds like the modulator is not working, I had my vacuum line pop off once and it acted the same way. Go down to NAPA and get an adjustable vacuum modulator, install it and see if it fixes it. They are cheap.

Tomi72

The guy who rebuilt the tranny came over yesterday to have a look. We removed the oilpan and completely disassembled the valvetrain of the transmission, nothing seemed out of place. With a vacuum pump we tested that the vacuum modulator is working as it should ( I had tested earlier that there actually is vacuum at the modulator when the engine is running). We also tested that the kickdown solenoid works. After putting everything carefully back together the problem still persist The stupid thing is that there was nothing wrong with the tranny, I just though that it would be a smart thing to have it checked while the engine was out

Maybe as a test I'll disconnect the vaccum to the tranny and check if the symptoms in my case would be similar to how it's working now


[Modified by Tomi72, 1:15 PM 6/30/2004]