rear end advise

[adm22]

The rear end center section / hogs head / differential / third member (I have heard it called all these things) in my car has been leaking for sometime and has also over the years gotten "Loose" so that when the car is in the air the drive shaft turns about 1/3 of the way before it will engage. Other than having to add fluid every so often I have not noticed any problems. The mechanic who does work for me that is beyond my skill level / easy to do with tools I own, recently convinced me it was time to replace or rebuild although could not find anyone who wanted to rebuild one- so repalce was the option.

I have a 2.75 9 inch 28 spline gears. According to who one talks to I have been told these are the best ones to have, the worst ones to have or else "granny gears". I rather like since they get me reasonably good gas mileage.

Found a junk yrad about 60 miles from my house in the oppiste direction form the palce the work was being done. They had "lots" of hogs heads and I could have my pick for $75, a price that sounded reasonable. The second one I tried was both a 28 spline and a 2.75 gear ratio. It was rather dirty as it had been sitting around for an unknown period of time and the old gear lube had attracted dirt. It felt tighter than mine so I bought it.

Got it to the grage and discovered after it all got cleaned up that there were several chips in the big gear on the flat sopts ot the top of the teeth- and that looks bad. So went back to junk yard and was told these do not matter it is the flat surfae of the gear that makes contact and these appeared for the most part to be OK. Was told good check the other ones and exchaneg if I wanted. After going through them all I could not find another that was the right gear ratio and right spline count. So I took advise of junk yard guy and decied to have the one I had bought the previous day put in. Was told if it was bad could exchange for another one BUT would have to pay the guys to look at full rear ends both on and off car to find it this could cost a lot of $$$.

So took it back nad reluctantly was told they would try putting in until they found a really big size chip in the smaller worm gear. This was really bad.

So they decided to put in a new seal so the grease would not leak out in the front and at the same time removed the thin "gasket" like thing and replaced it with silicon in order to tighten it up a bit.

It has indeed gotten tighter and I do not notice the clunk that I used to get when changing from forwrds to reverse and vice versa so this is a good thing. There is however a whine coming from the rear end when I decelerate. None during acceleration or when maintaining a constant speed. This I have been told is since the gears are now tighter.

This is not a good thing but wondering how bad of a thing it is. At this point I have driven it maybe 70 miles and it has not gotten any worse and perhaps lesseneed a wee bit- or I could just be getting used to it. Is this noise something that will disappear after awhile once the gears get used to meshing in their new positions or is this something that will wind up tearing things up and wrecking the gears that are when it was taken apart in good shape, especailly when compared to the one I just got?

The guy who did the work know it is not a good thing but is not entirely convinced it is a bad thing, especailly sicne it only makes the whine when it is decelerating.

 

[Don65Stang]

I'm not sure what engine and transmission you have but there is a large selection of gears in between what you have now and the "granny gears".

Try the spreadsheet at this link to see what different gears will do to your rpms: http://www.7173mustangs.com/thread-trans-gear-vs-rear-gear-vs-rpm-vs-mph

There is nothing wrong with stepping to a little higher gear. 3.00 or a 3.25 is not that big of a jump from a 2.75. If you want similar stay with a 3.00 ratio.

The new whining sound in my opinion is your car telling you that something isn't right. Will it break? I don't know but i do know that noises like that cause me to take action.

 

[adm22]

I have a 351c with a t5 transmission. Currently runs about 1500 revs at 55 MPH

Not sure what type of action to take if any right now- why I am posting. Although not planning any long road trips until I figure things out.

 

[tempestairbrush]

Did you put the origional "leaky" gearset back in the car or the one with the crackes in it. I personally would never put a chipped set of gears in a rear end, as any sort of chip or crack would be a sign to me that the gears life is over. When the guy put the "new seal so the grease would not leak out in the front " I am assuming you are talking about the pinion seal and he would have to pulled the pinion nut and pinion yoke, (where the drive shaft bolts too). If he torqued down the pinion nut too tight upon installation and put too much bearing preload on the pinion bearing this would cause the noise you talk about and in the future possably wear out the bearing.

 

[Don65Stang]

I have a 351c with a t5 transmission. Currently runs about 1500 revs at 55 MPH

Not sure what type of action to take if any right now- why I am posting. Although not planning any long road trips until I figure things out.

Are you sure your speedometer is correct? For a T5 with 2.75 rear gears my calculation is 1330 rpms at 55mph assuming a 26" tall tire.

RPM = trans gear ratio * (rear gear ratio * mph * 88) / (tire diameter * 3.14)/12)

In my opinion, a 2.75 puts the 5th gear rpms very low unless you're doing 90mph. Do you have any power in 5th gear at 55mph? I'd highly recommend a 3.25 rear gear. This would give you a great 1st gear ratio and 2000 rpm at 70mph. Just my $0.02.

 

[adm22]

Nothing from the junk yard piece was put into my car. What I beleive happened was that the seal at the front was repalced. When it was the small gasket like spacer that went between the main housing and the part that bolts in to the front was replaced with a seal of silicon. This got id of the loosness that it had but I suspect is also responsible for the whine.

He tried finding a new crush sleeve to put inot it but was unable to find one.

 

[matrixx]

I think you should def get it checked out by someone who really knows how to do ring and pinion gears. I notice in older cars you do hear more wineing noised in the drivetrain than modern cars but seems to be like this is a "noise that wasn't there before, only started when the rear was tinkered with" type situation. Fortunately my father is going to guide me along when i get to that project as he's been a ford service tech since i was born.

 

[Kermit 460]

If this could be of any help down the road, I am in the process of getting mine set up to 3.25 trac loc . When I do (probably this fall) I will not have any need for my 2.75 open 28 spline unit. I will see if it's still in decent shape when I get it out , so check back w/ me later if you still need a replacement.

Eric

 

[Silverback]

If it really does have that much slop in it I suspect that someone messed with it in the past and it's not setup correctly. You should be able to adjust most of that out _and_ get a decent pattern but it may whine if it has funny wear in it.

 

[adm22]

It does have a fair bit of slop in it and has lots of miles.

I had a wheel bearing go bad and break the axle just north of Atlanta anot 16-18 years ago. Wheel feel off and car skidded across 4 lanes aof freeway. If it had not been 2AM I would have really been screwed and caused one of those huge pile ups.

Place it got towed to put in an enture new acxle from junk yard housing and all. It had a higher number gear ratio and the car was having to do about 4k revs to do freeway speeds and gas milage suffered accordingly.

When I got home found the old gear ratio from a junk yard and had it put in. This is the one that was getting sloppy and has had at least 250k miles put on it since I put it in and an unknown number before that.

Just discovered the silicon seal does not appear to be holding the gear lube back and something is leaking.

 

[Silverback]

Ive never seen one with any amount of wear/miles with 1/3 turn worth of slop in it...

 

[tempestairbrush]

Sounds like its time to either replace with a good working third member or to find someone that know's what their doing to pull everything apart in that section and rebuild it, check gears, replace all bearings and seals, and reset all clearences and backlask. By the time you keep trying to hunt a couple problem's and keep taking it on and off the car, it would have been more cost effective to get everything done right and not worry about it anymore.

 

[RacerX]

The "gasket like thing" he took out is a pinion shim. Taking it out placed the pinion further into the ring gear resulting in a tighter gear engagement and the deceleration whine you describe. Usually when the gears start to whine, they are toast. I'd strongly suggest a new gear set and all new bearings thru out, but that's just the way I'd handle it.

Oh, and get another mechanic that knows how to set up rear end gears properly. It's not too difficult, just tedious.

 

[CZ-75]

I agree... just have everything replaced. The parts are not that expensive, and places like Jegs sell complete rebuild kits that include all the small parts you need.

 

[73MustangCoupe]

The "gasket like thing" he took out is a pinion shim. Taking it out placed the pinion further into the ring gear resulting in a tighter gear engagement and the deceleration whine you describe. Usually when the gears start to whine, they are toast. I'd strongly suggest a new gear set and all new bearings thru out, but that's just the way I'd handle it.

Oh, and get another mechanic that knows how to set up rear end gears properly. It's not too difficult, just tedious.

I agree completely. Pulling that pinion shim, especially if he didn't verify the wear pattern is a recipe for disaster. And who can't find a crush sleeve? They're at every "real" auto parts store. A new gear set, bearings, etc would be my preference, as well.

 

[mdan575]

I am actually going through the same sort of issues with play in my 9" axle. DS wheel has no play in it at all. PS the wheel was able to turn about an 1-2" without the Driveshaft turning. Annoying clunk in the rear when reverse to first or just taking off sometimes that has been getting worse. I contacted the guy in the link below and most likely I am gonna have him assemble a rebuilt 3rd member for me for $800 shipped. With Detroit Locker, 3.64 Gears, proper 4" yoke ready to bolt in. That way I can just worry about mine when I get around to it.

http://www.ebay.com/itm/161089875352?ssPageName=STRK:MEWAX:VRI&_trksid=p3984.m1423.l2661#ht_338wt_1161