Hello everyone.. My rear end was making some serios noise.. It sounds like it coming from the pumpkin, but I went out and bought new gear lub, recommended from the web site, aded the lsd additive, and sh'e still loud, my next step would be to change out my rear wheel bearings, is there a way to know for sure that they are bad without actually looking at them.... What else could it be? I am sure it's gotta be either one of the two. Any ideas?
Thanks Cruz,,,,,
oooh and yes I searched.....

 

Need some more info.

What kind of sound. Screech, rumble, whine? what kind

Does this sound only happen at a certain RPM, all the time, only in gear. Any speed in particular?

Does it happen when you arent moving?

Please more info

 

OK
the sound is whining, it gets louder the faster I go,
it does not do it when at stand still,
The sound is there when ever the car moves, I can barely hear it at less than 3 miles an hour, but basically any time the wheels are spinning the noise appears.
I just redid my interior and had the car stripped and boy was it loud then.......
It almost sounds like a fraking airplane in there.......
HELP!!!!!!!!!!!!!!!

 

Did u replace the sound deadening or is that now removed. Are there any other symptons or just the noise.

Our rear ends are traditionally noisy.

Wheel bearings as well as u-joints are usually more of a rumble than a whine.

Do you in fact have an LSD (what year and model is your car) Or just the diff.

If its diff then it will happen in a around corners, noisy all the time implies other things

 

ooooh I know our rear ends are noisey(that just don't sound rite!) I have had 8 rx-7's. Yes I am positive I have LSD, I have an 85 GSL-SE.. As for the sound deading,,, I put all of it back...
The car runs like a champ, besides this noise
there is no diferation in the sound, it only gets louder as I pick up speed.
When I take turns, nothing seems out of the ordinary, the sound stays contant, when I mean constant I mean even when I take a turn the sound remains the same, the slower I go the less I hear it the faster I go the more I here it. I checked u-joints and related components and everything is noce and tight, looks good...
The sound is diffenately something somethiong thats spinning
thanks
Cruz

 

u can prob check the e brake cable if its too tight, making the rear pads rub a lil to the rotors.. iono woudnt hurt to check

 

I had a similar sound. It almost sounded like a loud supercharger while I was on track. It's the rear diff going out. When you dropped the oil, how'd it look? Mine looked like dirty dish water.

 

Did you inspect the U Joint?

 

Lego... I hate to say it but I think your right that supercharger sound IS EXACTLY what I hear.... DAmn how do I know for sure? is there a test Ican do.....
My fluid when it came out was a black soup , when I removed the bolt on the bottom to drain it, I found fine shavings of metal attached to the magnet...
man this suck I hope it's not the diff but I think it might be,,,,

 

New oil doesnt rebuild, or even really help mask usually, a failing rearend.
There are serious forces at work inside a hypoid rearend.If the tolerances and contact points arent within a few thousandths of an inch,then there is going to be noise and rapid wear.....or catastrophic failure if its abused.

Check everything else first,as its going to be cheaper.
Wheel bearings,brakes,U-joints,driveline,anything that spins back there.Stuff like that is cheap and anyone can work on it.But if it comes down to a failed rearend unit,youll have to either school up on how to properly rebuild it,or pony up the cash for a rebuild or replacement 3rd member.Theres a reason a rearend build can cost 500 bucks or more,its not a simple or easy job compared to most automobile work.
Remember,were talking about the rearend drive gears,not the LSD or differential itself,so to speak,.....so it doesnt matter if its a GSL, or SE, or whatever.The drive gears(ring and pinion) mesh and transmit power at all times while driving.The differential gears inside the carrier only turn and mesh when going around a turn,so they are easier to diagnose when they fail.However,except for high torque/low gears 4x4's, its far more likely that the ring-pinion gears and/or bearings are worn out,than the diff spider gears.... since the latter dont turn much and are pretty long lasting.

 

ok thats some great info,,,,, I have checked the U-Joints, I have not inspected the wheel bearing yet, the brakes, rotors and calipers are new,.... I see the 3rd memnbers on sale on ebay all the time, would this be an easier process then trying to rebuild everything to spec... I have helped in quite a few engine rebuilds, nothing 100% on my own, so I can do a bit, but all....Any one in SW florida have a good GSL-SE rear end for sale?

 

With the GSL-SE parts being somewhat rare and sought after,you could also search for the more common 84-85 GSL rearend.It will still be LSD,but will have a slightly taller rearend gear.Its a direct swap in with very little change in behavior.
I recently switched from SE to GSL gear ratios during my rebuild and its not a very noticeable change at all.With the torquey nature of the SE engine,I doubt youll have any problems,and youll even pickup a few more MPGs on the highway since the RPMS will be slowed down some. And despite being worn out,you could probably sell the SE 3rd member for a fair price,possibly for more than you payed for the GSL unit.

 

Sounds like it's time to crack open the case and take a look things.

 

Usually ujoints and wheel bearings go out before the diff (unless the car has been seriously abused, repeatedly). Wheel bearings aren't too hard to replace, and usually bad ones have a sortof 'sandy' sound or rumble when you drive. Ujoints are a bear unless you've done it before, and then you can actually do it without a press. But I'd rather have a machine shop do it, sometimes they only charge about $25 for each R&R. The FSM says the Ujoints aren't replaceable, necessitating entire propshaft replacement ($450! or $250 for a mazdatrix aftermarket item) and one of the guys says the ujoints are just staked in so all you gotta do is deburr with a Dreml first.

 

My car whined loudly like that since the day I bought it. Very loud, and louder as you went faster. No change in noise when cornering. I could also feel some slop in the rear end as I engaged/disengaged the throttle while in gear.

I put over 30,000 miles on that rear end, then last spring swapped it out for a GSL unit which is nice and quiet. No telling how long the original would have lasted, I always expected it to go at any time. Didn't keep me from racing the car though. And it was still working well (if loud) the day I pulled it out.

 

Ours cars just dont have the torque or weight to grenade worn out diffs easily, I think.
Myself and others have proven what these units can take in regards to torque and longevity,provided proper care and lack of abuse is present.Shock loading and clutch drops will do them in,but normal driving or road racing,even with a pumped up N/A engine just doesnt work them that hard.

All these loud,but long lasting rearends sound like they are probably worn pinion bearings.The front pinion is especially small,and it turns at very high speeds.Loose,rough bearings make that sandy "pshhh" sound that gets louder with MPH.The slop induced by wear causes pinion deflection,which makes the gears push apart from each other and puts the contact points furthur up on the tooth,where its thinner and weaker.This allows for more oil to get in there and cusion things,but usually engine torque,a heavy curb weight,or towing/drag racing becomes to much and the teeth strip.With our cars being so light and rotaries lacking much lowend grunt,its easy to see why they just keep going and going.

 

I say its wheel bearings. U-joints will make a squeeking and clunking sound. My 82 was making a high pitched whine similar to what you post, and it turned out to be bad wheel bearings. Start there as its not a hard job and they are reletively cheap to buy. The sound did seem like it was coming from the pumpkin as well.

 

would you guys like me to post a video of me driving my old SE with a bad rear end for comparison?

 

[QUOTE=bliffle;7910432]Usually ujoints and wheel bearings go out before the diff (unless the car has been seriously abused, repeatedly).QUOTE]

I realize that but just saying it needs to be checked here for a process of elimination because it's in the general area.

 

My friend had the same problem...had a crazy humming sound when ever the car was rolling, or driving fast...never broke on him...he would drag race on it with no problem...but the humming was crazy loud...

Putting in new oil in the diff will no cover up the problem or hide it...Your going to have to go in and get down and dirty to see what the problem is...before things get worse...

 

The more I think about it the more I worry that it's the differential. But it's easy enough to check or replace the wheel bearings and ujoints.

The differential is a very ingenious and useful invention, given all the things it must do, and it's even more amazing when you add in LSD, so it pays to take good care of it.

Are the 85GSL and 85SE LSDs really interchangeable? For some reason I have it in my head that they are different and not interchangeable.

 

they are different on the inside (teeth coarseness and whatnot), but you can use an se diff on a gsl, just not sure what mods are needed if any

 

Since you say you have an 85, that means you have NON replaceable u-joints. You can check them, but if they are tight, they are fine. If they aren't, its time for a new driveshaft. I will place my bet on wheel bearings though. It could be the differential, but before you go spending a lot of money on a new diff, PLEASE replace the wheel bearings.

 

The GSL-SE rearend is the exact same unit as all the others,it just has a different gear ratio......4.07 vs 3.90 for the 12A cars.There were coarse and fine tooth rearend gears throughout the 1st gen production run,although I have not seen any 4.07 sets that were coarse.Typically,the coarse sets are on the older cars.
The LSD unit and diff carrier are the same units from 81-85 for all 1st gens.The only changes made were for 84-85 cars,the side spider gears had bigger splines to accept the bigger axles,and the SE had its LSD plate stack modified to work with the stronger engine.It was actually made LESS aggressive,presumably to combat lock up and oversteer induced by the torquier 13B.

Heres a breakdown for the LSD units.......

https://www.rx7club.com/1st-gen-archive-71/drivetrain-gsl-se-lsd-teardown-pics-drivetrain-tutorials-coming-soon-717591/

 

You have probably tried this, but put the car on axle stands and spin the wheels and try to locate if the sound is coming from the dif or the wheel bearings.