# Zumbrota Differentials



## CaptPuttPutt (6 mo ago)

Do these differentials elimate gear whine? Thanks!


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## lust4speed (Jul 5, 2019)

Gear whine is caused by the pinion and ring gear either being set up wrong initially, caused by lack of lubrication, or internal parts slipping out of alignment due to breakage or excess wear. Once you get whine it almost always calls for a new gearset to restore quiet operation. 

I did some quick reading on their website and looks like they rebuild old units. I also didn't see anything older than 1972 listed on their site. They could build a good unit but so can many shops located around the country and it would save shipping costs to find a local shop to do the work - it just takes some investigating to insure you find a good shop. Also if something goes wrong you really don't want to ship the rearend back to them for repair. 

If you are looking to go with something beefier then I would be looking at Currie, Moser, or Strange Engineering for an aftermarket replacement. If you plan on staying stock then definitely find a good local shop to do the work.


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## armyadarkness (Dec 7, 2020)

CaptPuttPutt said:


> Do these differentials elimate gear whine? Thanks!


You didnt list any of your car specs, but if it's 55 years old and either sat for a long time, had no routine maintenance, or both, then your bearings and ujoints could be wiped!!!

Im a 2nd owner of a garage kept car with 70,000 miles

And:


The ujoints were rusted dry and almost seized
The axle bearings we're bone dry, rusted, and almost seized
The pinion bearing was shot
The car whined LIKE CRAZY!!!!!!!!!!!!! It was super loud.


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## armyadarkness (Dec 7, 2020)

Ive never seen an owner service wheel bearings. In the rear axle, they're sealed units, so once the grease dries up, they're done.

Most people would consider themselves lucky to get 20 years out of a bearing that was never greased. Also, the bearings are what hold the axles in, so if you suspect this to be an issue, dont push it.

I would:


 Replace the axle bearings and seal
Service the ujoints
Inspect the diff
And then report your findings.

If the pinion bearing is shot or the gears are shot, you'll see from inspection.


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## CaptPuttPutt (6 mo ago)

lust4speed said:


> Gear whine is caused by the pinion and ring gear either being set up wrong initially, caused by lack of lubrication, or internal parts slipping out of alignment due to breakage or excess wear. Once you get whine it almost always calls for a new gearset to restore quiet operation.
> 
> I did some quick reading on their website and looks like they rebuild old units. I also didn't see anything older than 1972 listed on their site. They could build a good unit but so can many shops located around the country and it would save shipping costs to find a local shop to do the work - it just takes some investigating to insure you find a good shop. Also if something goes wrong you really don't want to ship the rearend back to them for repair.
> 
> If you are looking to go with something beefier then I would be looking at Currie, Moser, or Strange Engineering for an aftermarket replacement. If you plan on staying stock then definitely find a good local shop to do the work.


Background:

2005 GTO - Automatic - 17800 miles - Gear whine decelerating from 50 to 35 MPH from day one. Second owner. General Sales Manager stated he never heard any whine when he drove it. Dealership refunded me $1000.

My mechanic (did all the work) rebuilt the diff minus the ring and pinion. No help.

Installed a brand new ring and pinion (Motive Gear 3.70). OMG! Constant Racket.

Another mechanic nearby (Owner of three Aussie rigs that all whine) advised putting the original gears back in for some semblance of quiet!

Sure enough, the whine was now most noticeable decelerating from 50 to 40, but now sporadic whines occur above 30 mph. Nerve Racking!

Car is up for sale on Portland OR craigslist (Yellow Jacket)

Many Thanks for your input!!

p.s. Zumbrota does rebuild these diffs.


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## CaptPuttPutt (6 mo ago)

armyadarkness said:


> You didnt list any of your car specs, but if it's 55 years old and either sat for a long time, had no routine maintenance, or both, then your bearings and ujoints could be wiped!!!
> 
> Im a 2nd owner of a garage kept car with 70,000 miles
> 
> ...


 2005/Automatic/18700 miles/ Second Owner/ Whining Differential/No known sit time


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## CaptPuttPutt (6 mo ago)

armyadarkness said:


> Ive never seen an owner service wheel bearings. In the rear axle, they're sealed units, so once the grease dries up, they're done.
> 
> Most people would consider themselves lucky to get 20 years out of a bearing that was never greased. Also, the bearings are what hold the axles in, so if you suspect this to be an issue, dont push it.
> 
> ...


The differential is the Problem Child! Please read my response to "lust4speed". Very much appreciate your inputs!


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## armyadarkness (Dec 7, 2020)

Got it. Didnt have much to go by from your original post, which is why my response was aimed at 1965-1974 GTO's.

I did have a 2006 (family member car) with bad axle bearings and since it's such a common problem on them, they make a sleeve kit for the axles, but it sounds like you already solved your issue.


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