7.5" problems

[hilltopfarm]

I have a 88 ranger 4x4 with a 7.5 axle. When I am going at freeway speed (60mph +) There is a loud "hum" from the rear end as long as my foot is on the gas, when I let off, the sound goes away. When this happens a new sound appears, this one a high pitched whine. This sound is with it coasting. I think that sound number 1 is the diff. and number 2 is wheel bearings???? I was going to fill the diff with Lucas oil and some friction modifier and see if that helps. Also after getting home the other day, I checked the temp of the diff, it was so hot you could not touch it without getting burned. Seems like something is wrong here. Any suggestions as to what I should do?? Maybe put Lucas, or Synthetic in it?? Check the wheel bearings??

Thanks

 

[doorgunner]

Check the pinion nut to see if it backed off a little....she pinion shaft will have a little in/out/up down play & cause similar noises....

check for bad rear end oil before adding anything...no sensense in mixing good with bad!!

 

[hilltopfarm]

Check the pinion nut to see if it backed off a little....she pinion shaft will have a little in/out/up down play & cause similar noises....

check for bad rear end oil before adding anything...no sensense in mixing good with bad!!

OK, how hot is that diff supposed to get? Too hot to touch? Also what is an indication of bad oil in it?? I'll check the pinion nut, see if that is the issue.

Thanks

 

[kagedws6]

not to scare you but thats the noise my truck made on tuesday on my way home from work. didn't drive it wed. thursday morning I didn't make it off my street before it locked up. I'm ripping it open tomorrow

 

[hilltopfarm]

I just drained the oil and refilled with Lucas synthetic. Sounds better at low speed, we will see how it is on the highway when I drive to work on Monday.

 

[kimcrwbr1]

To check your wheel bearings grab the tire on the top and wiggle it side to side real hard if you hear a clumk at the wheel the bearing is going bad. Pull the wheels and drums and look for oil leaks. To check the pinion and ring gear put the tranny in neutral and grab the driveshaft and wiggle it if there is any movement it could be a bearing going out look for fresh oil out the seal. The housing should never get to hot to touch your gonna want to keep an eye on it and start looking for a replacement or having that one rebuilt, was there any metal in the old gear oil. Hopefully it was just low on oil and you didnt damage the gears or bearings start researching your options now and plan on a rebuild or a swap!

 

[wild horse]

My diff's get hot enough to fry an egg on but I've never had any problems with them but I would look into doing a swap because the Dana 28 and 7.5 are junk axle's and my brakes don't work very well with my 36" tires, But other then that
just make shure your berrings are good and your pinion berring is not on it's way out and change the gear oil if it's wore out.