My truck won't accelerate properly

Question edited for clarity and spelling.
Question moved to model category from 'Misc'.

Check for Diagnostic Trouble Codes. check clutch operation if manual. Check transmission fluid if automatic.

Hello,

Was the transmission fluid level excessively low for a prolonged period of time because of the leak?
If this is the case this could have caused a front pump failure in the transmission (TH350, TH400). Or I suppose a tranny sensor could be to blame. Often the OD (Overdrive) goes out before the rest. At a local transmission shop in my area for a bench job (you take out the tranny and they do a rebuild and you put the tranny back in) is about $400 for a Turbo Hydro 350 automatic, $425 for a 5-speed manual with new synchroze.
I hope this helps.

Check the:
- Fuel pump pressure and regulating valve.
- Check the ignition system.
- Air leaks. (Throttle body gasket, idle air control valve shucked open, PCV valve open, vacuum hoses, gasket intake manifold, A/C VSV).
- Muffler.

Transmission fluid! You need to find the leak and stop it; top up the transmission before it is damaged. Check the lower pan for a gasket leaking and examine the transmission fluid cooler lines running to radiator or to in front of radiator.

I'm guessing you mean transmission fluid poured out? That would certainly explain why it won't move. The most common leak point for older automatic transmission cars are the transmission cooler lines. They run from the radiator to the transmission (the cooler is built into the radiator) and they are made of steel so they are prone to rust. I would start looking there. The other leak points would be the lower pan, axle seals, and where the case bolts together. Take a look at the radiator and you should see some small steel lines bolted to the radiator. Follow them and look for heavy rust that is wet with fluid.

Check your trans fluid level (car must be running to perform this properly). If it is low, there may be a leak, check the transmission oil lines on the radiator for leaks. If ok, try flushing then replacing the transmission oil and filter. Its not guaranteed to work!! Over heating does damage the transmission. Reason is, your trans oil runs through the radiator to keep it at a controlled temperature. When the engine overheats, the radiator becomes extremely hot which in turn heats up the transmission oil instead of cooling it. This may or may not cause severe damage!!

Dont throw it off a cliff just yet :-) Just check the vacuum line from the inlet manifold back to the transmission, ensure that fittings are air tight and that there are no holes in the line.
Explanation for possible fix:- When the car is at idle the inlet manifold plenum has a reasonably high vacuum generated within it. The vacuum line to the transmission conveys this drop in pressure to the shift solenoid. When you accelerate slowly you hardly open the throttle and the vacuum remains high in the system. The solenoid allows early shifts through to the higher gears. If you accelerat hard the throttle is open wide and hardly any vacuum is maintained. The shift solenoid, in the absence of vacuum in the line, now holds each gear for much longer allowing the engine to use its full power band.
If the inlet plenum suffers from an air leak or the vacuum line to the transmission becomes loose or a leak develops in it the solenoid reads this as if the car is accelerating hard and wants to hold each gear for as long as possible. This situation sounds like your problem so check that everything is free of any possible leak. If you find a leak and cure it not only will the shift pattern be fixed but your engine idle will be much better too.

your vacum leaks has alot to do with it have vacum leaks fixed auto parts store sells the correct size hose you need at a ver fair price fix vacum leaks first then see how it runs after thatcheck fluid level in transmission and change transmission filter

Hi,

This sounds like you have a dirty transmission filter . I would change the filter and transmission fluid on it . That should fix the problem but if it does not check the vacuum line to make sure it is on and not leaking.