f-150 bucking, help - Ford Forums

Jac4387 · 02-07-2004, 09:01

i have a 1990 f-150 with the 4.9L i-6 and e4od transmission. when i first baught the truck it ran like crap and bucked really bad when driving. I replaced the spark plugs and ran fuel injector cleaner and it ran alot better. Since then i had the transmission replaced with a used one. it ran good for a day or two, but then started to rev high and shift late when changing gears, it acted like it was low on ATF fluid so i checked it and added some, i might have over filled it a bit :( but its not shifting as bad anymore. so my question is, what could the bucking be, i dont think its the transmission because its done it with both transmissions, and it ran better once i changed the plugs and ran the fuel injector cleaner. And second, what could be causing my transmission to shift late?

'92BigBronco · 02-07-2004, 11:57

It sounds like you may just need a good tune up. Changing the spark plugs is a good start, but changing out the plug wires along with the distributor cap and rotor surely won't hurt. If a tune up doesn't fix your problem, you know to look further into it.

As far as the tranny is concerned.....all I can say is that I hope you got some sort of money back guarantee or warranty. Buying a used tranny is never a good idea if you depend on the vehicle for reliable transportation. Low tranny fluid will cause erratic shifting as will having a brake light out along with a few other electrical problems but more often that not the clutches are worn....causing the high rev shifts you're describing. The E4OD tranny's shifts, line pressure, torque converter lockup, etc. are all electronically controlled, making it hard for someone other than a qualified transmission shop to diagnose the problem/problems. Have it checked out by a well known shop in your area and you'll know exactly where you stand.

Jac4387 · 02-07-2004, 12:07

it only seems like the problem is between 1st and 2nd gear, drive and reverse and the rest of the gears engage firmly so i dont think its the pump. i have a 30 day warranty of the transmission, im going to take it back on tuesday to have them check it out.

'92BigBronco · 02-07-2004, 14:13

The 1-2 clutch pack is the first to wear out as it gets the most abuse. You have a warranty, so you should be ok.

Good luck!