O/D Failure? Engine?

[MN88k1500]

1988 Chev K1500, 350....

Had a hesitation after maybe 10 miles whenever I'd be on a highway/freeway and have to decellerate below 55 and accellerate again. Recently had EGR valve replaced and no longer have a check engine light come on, but the replacement did not solve the problem. As long as I'm able to get the truck to 55+ MPH and am able to maintain that (no need to pass anyone, brake for any reason, etc.) I don't have the problem, but the first time I have to brake/slow down after cruising (not meaning using cc) the truck chugs upon acceleration and the only way I can get it to stop is by gunning the gas so it downshifts.

I decided to try driving in Drive rather than O/D and only once did it hesitate after deceleration. I got my speed up to 55 and it was running just fine today so I popped it into O/D and it instantly started to hesitate.

What's the deal? The tranny has been rebuilt and it has a used transfer case. I didn't have the work done, the previous owner did but gave me the paperwork for reference/proof. It was changed less than 30K miles ago, but the mechanic's warranty has expired.

Any suggestions? Do you think it's the tranny?

[gmsmallblockguy]

Well hrmm. Sounds like it hesitates at low rpm under load, but runs well at high rpm.
Several possible causes come to mind.
Worn cam.
Low compression.
Bad accelerator pump.
Weak coil.
The only tranny related thing I can think of would be failure to kick down.
Vaccum leak.
Loose spark plug.(s)

[Thunderbolt]

I am not sure what the exact procedure is to adjust it, But it sounds like your detent cable is not adjusted properly. If these are not set right it will cause the trans to not shift into overdrive properly.It can also cause drivabilty problems because the trans isn't sure what to do and it could also be something with the TCC solenoid.

[chevytrucks92]

Could be like previously mentioned the distrubator cap or it could be the torque converter. Mine went out while the truck was still under warranty (118,000 on it now) and it did similar to what you just mentioned. It would vibrate terribly bad when shifting from 3 to OD. It would only do it for just a few seconds, but it was a BAD vibration. Turned out the converter was going down so that could be your problem. I think you'd be better off if it was a cam though, lol becuase having the converter replaced will be big dollars!

I'd try changing the cap and rotor first, and if that didn't cure ya, then you may have a converter going down.

[Thunderbolt]

If it is the torque converter shuttering it doesn't mean for sure the converter is bad. You can pour a can of friction modifier it the trans and many times this cures the problem. If the dentent cable isn't set right the TCC will not lock up properly causing torque converter slippage which causes excess heat and glazing which in turn can cause it to shutter mild to severe when going from 3rd to overdrive. The friction modifer many times will cure the shutter, But if the converter is slipping it will do it again. It can be the converter going bad or the lockup. I would do as others suggested and do a tune up first and see what happens.

[MN88k1500]

Thanks. I'll be having the mechanic give it a good once over since the piece of crap blew the belt and PS pump...and that's just the obvious. Once it's fixed I'm putting it up for sale.