Realize this belongs in the trans forum but wanted to post it here as well in the hopes someone has experienced/fixed this problem.
My '92 300-6cyl E4OD with 105K is shifting hard. When easing away from a stop sign at moderate throttle, the trans will shift hard on the 1 to 2 shift. It's hard enough to snap your head. It also does the same on the 2 to 3 shift. It only started doing this recently and it also doesn't do it every time. It will do this for 2 or 3 days and then it will shift normally for a week and then back to the bang shifting. If during the days that it is bang shifting, I can accelerate really hard, it will shift normally thru the gears. It only happens when I am easing away from a stop and accelerating non-agressively (moderate throttle input). I bought the truck with 80K (now have 105K miles) and have changed the fluid/filter twice in this time period. Everything appears normal on the trans, no leaks, good trans fluid color, no unusual noises, OD functions normally, etc. Anybody experienced this?
Thanks, Charles

 

My 1988 Extended Cab, 302, AOD with about 90,000 miles does the same thing--shifts smoothly when I accelerate hard, but at slower acceleration it shifts up at lower rpms with a real "thunk", and similarly if I decelerate slowly, it also thunks quite hard. Any ideas? I understand that there are no adjustments to be made on an AOD transmission, and the fluid looks/smells fairly clean, and was last changed about 30,000 miles ago.
Thanks,
Frank.

 

Well looks like we're both experiencing the same problem. I'm sure this will eventually damage the transmission. Hopefully someone will chime in with some things to check and a fix. Charles

 

Pull your diagnostic codes. You could try a few cheapies first. Make sure all your vacuum lines are in good order. Vacuum lines control more than half the emissions systems under your hood. Clean the IAC (on top of the throttle body). There is a switch inside the IAC that gets coated with carbon, spray it off and q-tip/acid brush the carbon out. Throttle position sensor may need replacement. More expensive...manual lever position sensor, search MLPS here.

 

Alot of the time when your trans starts shifting hard the fluid is burnt. Try changing your fluid and if it smells when you are changing it you will need to drain the converter also. I have heard of this happening to a few F150's. Sometimes it is a early indication of the converter starting to slip and burns the fluid. Hope this helps

 

Mine shifted hard too until I put a can of seafoam transmission tuner in it. Took it about 200 miles but it smoothened right up. I've got good smooth shifts now. That seafoam stuff is good on whatever you use it on.

 

Not to butt in, but what does burnt tranny fluid smell like?? Would you be able to smell it outside the truck after a ride?? Also, can you tell the quality of the trany fluid by lookin at the dipstick??

 

The fuel injection computer regulates transmission line pressure using the EPC solenoid.
If the computer finds certain inputs not to its liking, it can put the transmission into "performance mode" -- it raises the line pressure to the point that the transmission shifts hard. This is especially noticeable on the 1-2 shift.

Performance mode is an endeavor to protect the trans. The higher the line pressure, the harder the shift, and the less slipping of clutches and other internal components. Hard 1/2 shifts caused by typical "performance mode" will not damage the trans; though the situation is annoying and you may think that damage is happening.

Pulling codes can sometimes get the computer to reveal what sensor it thinks is out-of-spec. The most common culprit is the MLPS on the side of the trans -- the early design was susceptible to water splashing and corrosion. The next most likely possible problem area is the VSS sensor -- if the computer thinks the trans is slipping because the VSS input is not consistent with engine RPM it will go into "performance mode". A worn torque converter clutch is another more distant possibility -- too much slip = performance mode. The TPS on the throttle body is another possible, albeit unlikely, suspect.

You might try a search on "E4OD Hard Shift" for more on this.

 

Thanks for all the replys.
fefarm, looks like you have given me some things to check. First item will be to pull the codes. Thanks, Charles

 

My E4OD started shifting really hard when I ripped the wiring to my VSS. Fixed that and it was fine.

 

i just went through the same thing just last week . i have a 91 ford f-250 4x4. same exact problem. went and had codes pulled and it turned out to be a bad speed sensor on the trans case. replaced it and all is well . cheap fix $17.99 at autozone. giv it a try .