I have a 1984 Z28 with the carbureted HO 305 motor and an automatic transmission (TH700R4 I think). Here's the problem. When the car shifts to higher gears it starts "jerking". Basically the engine seems to surge then back off, then surge, then back off. It is more pronounced under heavy load. Giving the car gas has no impact on this. Backing off the throttle seems to allow it to shift more easily however the problem seems to be getting progressively worse. In the past I needed to really step on the throttle to cause it to happen. Now it happens under much lighter load. I have recently changed the transmission fluid and filter. Any troubleshooting suggestions, ideas about what is wrong or suggestions about what I can do to fix it would be greatly appreciated.

 

does it just jerk once when shifting like a hard shift or is it more like a miss like running out of gas?

 

It is more like it's running out of gas. When it is happening, if I shift into neutral I can rev the engine with no problem but when in gear it suffers from the problem.

 

im thinking its engine instead of transmission I would suggest checking timing and spark plugs/wires transmission is usually hard shifts or like a lag when giving gas

 

but u said its fine when in neutral how long has it been doing it

 

The plugs, wires, distributor cap, carb are all new and it runs fine when in neutral. I may be doing a bad job explaining what is happening. At about the time the transmission shifts into a new gear the car loses power and the tac drops down, then surges, drops, surges, drops... If I step hard on the gas, nothing really happens. If I back off the throttle it smooths out. Originally, if I kept off the gas (light throttle) it would shift fine. Today it got much worse and did the drop/surge thing even under light load. I basically "limped" home. I immediately checked the transmission fluid and it was full. This has been happening since I got the car back in August. I've probably put 1,000 miles at most on the car since I have owned it.

 

Maybe it's a dirty fuel filter.

 

it very well could be fuel filter as long as it isn't shifting hard and tranny fluid looks clean I would rule out tranny and first focus on fuel system are you getting any backfires? timing could be slightly off do you have a cam or anything done to it? my suggestion would be check fuel filter, double check timing its a new distributer but could be slightly off, do a compression check, then do a fuel pressure check, and check for leaks in vacuum hoses. if all those turn up good come back and well go from there

 

When I have my TCC lockup engaged, I experienced the same jerk and hesitation you're explaining.