My 98 F150 4x4 (automatic) ext cab shakes when I start driving...Its only for a second... Its as soon as I start from a stop... also does it when I reverse from a stop...its not all the time but its enough now to concern me...Any Ideas? Any help would be much appreciated...

 

Are you turning at all, or just going straight? This will make a difference in the source of the problem.

 

Good question, I wanna say it happens when Im turning.... although I believe its happened when Im going straight as well... sorry ...this prolly doesn't help haha...Also it seems to be a shake coming from the middle or the rear of the truck...I can't tell for sure though...

 

Sounds like your clutch packs in the posi unit are the culprit. They are binding on slight turns while accelerating. Best way to repair is to replace clutches. You could try adding a bottle of friction modifier to the rear end and see what happens. It is only about $8 from your local dealer. Clutch kit is around $140 plus fluids and labor (about 3.5 hours).

 

Do you have mudders?

 

No mudders on the truck.....I have noticed a shiny spot being worn on the drive shaft right where it meets the transfer case...Is that normal?

 

That's just where the shaft slides in and out of the case during suspension travel. Normal.

 

i'd check the slip joint on the driveshaft in the back of the tranny. might just need to be lubed with a good synthetic grease.

 

cool, thanks guys much appreciated ...I'll look into it... Also at one time I had a ranger with a U joint on the drive shaft that was frezzin up...It made the same kind of shake when I was starting off driving ...do you think it could be something like that?