i've got a 77' f-100 302/c-4 tranny 2x4. i've been doing alot of work on it lately, eliminating leaks etc. two weeks ago i replaced the rear shocks. my roommate jacked the truck up while i went and got the shock absorbers (he jacked it from the axle housing). i replaced the shocks and noticed last week that it was making a strang sound when i put it in reverse (like a rubbing, it almost stalls the engine out.)
it also makes a sound when your driving and your on the gas and then let off. the sounds are coming from the rear area. i looked under the truck and noticed it was leaking out of the axle housing. its never leaked any gear oil and i wonder what it could be. all i've done to the rear of the vehicle lately is those shocks.
if anyone can help or has knowledge about these areas it would be appreciated. thanks.

 

First and foremost, where is it leaking? From a crack in the housing or tube? From the gasket around the diff? From the yoke area?

As for the sounds, assuming it's a 9" rear end:

I'd jack it up and pull the axles and diff. Take a close look at the ring gear, pinion gear, axle splines, and outer bearings. Also look at the spider gears. What you're looking for is severe wear or chipped teeth and splines.

Check to make sure there's a little play between the ring & pinion gears, and that the carrier bearings are in tact.

It could be the carrier bearings, outer axle bearings, pinion bearings or almost anything. But, based on when it happens, I'm leaning toward the gears.

It could also be as simple as the rear brakes being too tight so check those as well.

Does it make noise when you just roll in reverse or only when you apply power in reverse?

Kevin K.

 

thanks for info. kozak. this is one area i'm not too familiar with. i'm going to break the whole thing down this weekend.
as for where its leaking from, it's really hard to tell. i need to clean it real good and watch, but it only starts after i've been driving. so it's all wet by the time i stop. it really looks like its coming from the front of the housing (by the u-joint)
in reverse it starts the noise after i start moving and when i let off the gas it starts to shimmy and vibrate. my idle starts acting like my truck wants to go dead.
what really confuses me though is if i'm on the highway it makes no noise while i'm really haulin' it, but as soon as i let off the gas it starts that sound like somethings rubbing. why wouldn't it do it the whole time i'm driving?
well thanks again and reply back if you have any more ideas or questions.

 

Any time you have a leak in the rear axle, the first thing to check is the breather tube. That's the rubber hose that comes off the axle tube where the metal brake lines meet on the drivers side. One rubber hose is the brake line and is part of the brass fitting. The other is the breather and should just be hose-clamped on. If that's clogged, pressure will build up inside the axle and force the lube out the seals.

If it's leaking from the front where the yoke (that the shaft is connected to) comes out, it's probably your pinion seal. The seal is pretty cheap, and pretty easy to change. But you have to get the yoke off. There's a big nut that holds it on that gets torqued to something like 220 ft. lbs.. If the bearings for the pinion are ok, you'll just have to re-torque the nut after you change the seal.

If the pinion bearings are bad and need to be replaced, there's a little more work involved. You'll have to mess with shims and the crush collar to get the preload and gear mesh pattern right. There's a tech article on building a 9" rear end on this site that explains this process in detail. I'd read it a few times as it will tell you everything you need to know about the 9".

Bad pinion bearings could cause the vibration/noise problem you describe. Remove the drive shaft and try to wiggle the yoke up and down and site to side. If it moves, it's the bearings.

Good luck and let us know what you find when you take it apart.

Kevin K.