View Full Version : Tranny hickup??

08-13-2007, 09:04 AM
Need some help to potentially spare excessive shop hours. .

Before I moved I put on new set of GT40P heads. I took it our for the first time on Friday (don't laugh - I've still been able to ski with Footin'). The engine runs so smooth, fires right up, no leaks, it seems like we are good to go, but I was very anxious to find out if all of my work would prove seemless.

When first backing off the trailer I thought I felt a little hickup in the tranny. When idling out I felt it again about once every three seconds at 1,000 RPM. The hickup feels like a quick loss of forward motion.

1 Drive Shaft out of alignment?
If this were the case I think I'd feel a vibration at every revolution

2 Fuel delivery?
I just reused the intake manifold in my 93 which came originally with GT40 heads so the intake should match up I could be wrong, but it sure runs smooth when the transmission is dissengaged (on the trailer or in the water)

3 Transmission is slipping?
I would think if this were the case I'd likely get prop spin with the transmission is dissengaged and I don't. Please someone tell me all I have to do is drain and refill my transmission fluid.

4 Transmission has gone to crap mysteriously while it was in a truck for 3,000 miles.
Oh crap.

08-13-2007, 09:49 AM
Never re-use gaskets. It's not worth the amount saved. What about head gaskets? You replaced them, right?

If the only work done was to replace the heads and the motor never left the boat, I seriously doubt that the transmission is to blame. There's really no logical reason to suspect it, even after travelling 3000 in a truck.

08-13-2007, 09:57 AM
I used all new gaskets, and new bolts.

The main reason that I suspect the transmission is that the engine runs fine when it's not in gear. I know dynamics change when an engine is under load but I would not have suspected by this much.

Any other thoughts?

08-13-2007, 09:58 AM
Could have have a valve lifter torqued too tight, either not letting exhaust out or fuel in? Again, it seems like this would happen every time the cylinder fires and the sudden lags are not happening that fast.

08-13-2007, 09:58 AM
Double post

08-13-2007, 10:12 AM
Do a compression and/or leakdown test. A motor can be smooth as silk in neutral and lumpy as he!! in gear. If you had to adjust your rocker arms with the different heads, I would go back and re-check the tolerances.

08-13-2007, 10:15 AM
Thanks Jim!