What a great truck! Just picked up a '96 T100 Extra Cab 4wd automatic this weekend- 244K miles and you'd never know it. A great truck, light years ahead of the '94 F150 I had for a year. Fix Or Repair Daily is an understatement.

A few issues-

Rear diff might need service/repair. Driving down a hill at 50-60 mph, lift throttle, get a vibration in the rear. Much like my Chevy work van, and I'm pretty sure that needs a rear end too. T100 also has a pretty decent vibration at 65-70 mph on the highway, goes away above 70.

I read a great page (Erik's) about diff types, and I'm looking for stock replacement advice/parts sources. I'm a competent weekend mechanic but I think diff replacement is above my pay grade. Any suggestions?

ALSO - Valve cover gaskets are leaking. Looks minor, but can make a stink. I need to buy a Haynes manual, and make a weekend of this repair. Anything else I should look at/repair while I've got the intake/covers off???

Horn- doesn't work. I haven't tested anything, but I understand electronics well. Do these trucks have a common failure point (horn pad, wiring harness, grounds) or is this a rare failure?

Thanks for reading this far- this looks like a great forum!

 

your vibration in the rear end is probably your u joint that needs to be changed, and the vibration between 65 and 70 is probably and alignment issue or u need your tires balanced but i'm leaning more to u just need to take your truck to get it aligned.

 

244k miles, it is probably time for replacement. I would go for a salvage yard third and see how that goes. You might also want to go through your rear driveline while you're at it, making sure the two-piece driveshaft is up to spec, and doing the wheel bearings and seals. The vibration at 65-70 could be anything from out-of-balance driveshafts to out-of-balance wheels/tires. I rather doubt that it is alignment unless you're feeling it through the steering wheel. If it feels like it is coming from the rear, it is most likely somewhere in the rear driveline.

Without the specialized tools to do a full-on diff third setup, I would give it to a shop. If you're just going to replace the third, that can easily be done by yourself with some help.

Just do an all around check of the belts and such.

Not sure on failure points. If you have a multimeter, check to see if you get voltage on the leads at the horn. If you do, replace that. If not, work your way back.

 

Yeah i think with the vibration it would be the rar u-joint. its a chap fix and lik the other guy said--probobly time for a change anyways.

but at th sam time i would get all the tires rotatd and balanced. because that can always make a huge difference. and with the rear end--just swap it out. its cheapest and easiest. you can find a used one pretty easily.