I have an 88 i just got back on the road and sometimes when I am launching from a stop the car doesn't want to shift and so it hesitates, doing so builds up some power and it barks the tires.
what could be causing this?
i don't mind getting jerked in the seat but if any cop saw he'd probably tell me off because he thought it was me, and I don't like the idea of something being wrong with the transmission.

 

I am assuming your '88 is a V12??.

The trans should not jerk like that, full stop.

It may be waaaaay overdue for a service, and filter change.

It may be a failed vacuam modulator, or the vacuam hose supplying it with operational vacuam.

The governor gear MAY be stripping, it does happen, and hence oil pressure in the trans is not as it should be.

Start at the beginning, service the transmission, check/replace the modulator and its hose, see what happens, you cannot make it any worse. If it still plays up, remove the governor assembly, RH rear of trans case, and replace the nylon gear (GM part), and then if its still iffy, see a trans specialist.

The TH400 is strong and reletively trouble free apart from the above, but lack of service will certainly give trauma.

 

shes been sitting since 97....so yeah there is a lack of service. for the most part its good, but this has happened 2 or 3 times in the first 100 miles i have put on it so far.
yeah its a v12.
I need to get a filter for it but i wouldn't be too surprised if the vacumn was acting up.

 

Sitting for 13 years?

IMHO this car needs ALL new fluids, if you haven't already done so.

Relative to your other posting about rear brakes not working, the system is probably well rusted. Brake fluid absorbs moisture so the brake system takes a beating when a car is stored.

I agree with all of Grant's advice mentioned above. The only thing I'd change is the order of doing things. A failing modulator (or modulator vacuum hose) is the most likely cause. I'd go there first. If that fixes the problem and the trans shifts normally, I'd temporarily move on.....and attack the braking system !

Cheers
DD

 

yup 12 years. and between 93 and 97 she only went 7 thousands miles.
Im expecting to find the vacuum hose partially cracked.

and yeah, I agree, I'd like to get the brakes fixed most of all right now