# Rear End rebuildable?



## cruiser787904 (Mar 9, 2007)

Alright I took my 04 GTO to the dealer today to get a new clutch on the AC Compressor under warranty and have the rear end checked out for a noise when starting off in first gear or reverse. They fixed the AC and said the noise from the rear end is actually the exhaust Rattling which is what I thought but thought I would have them look at rear end just in case.

I asked them what they recommend for service on the rear end. He said he only recommends GM Synthetic fluid with no additives. No big surprise there. What he said next I found odd. He said that the GTO rearend is non-serviceable and that there is no rebuild procedure in place. So if the rear end blows you simply need to replace it. Since I have heard of people swapping gears and such how is that even remotely true.

Can you rebuild the rear end in our cars? Being a pretty savvy mechanic I would have to say yes but I have read something about laser alligning the pinion shims or something in those regards. Any info would be great for moving forward....

Oh yeah I am draining the diff and adding Royal Purple this weekend...:cheers :cheers


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## mtjoy (May 3, 2007)

The diffs in these cars can be rebuilt. They are a little pricey, but here are several sites to check out:
http://www.difftechnics.com.au/
http://www.midwestpd.com/catalog/index.php?cPath=412_190_193

I've got a spare diff if you want to buy an extra one.


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## svede1212 (Nov 1, 2005)

yes and dyno oil has worked better for me than synthetic in the diff. i used Royal Purple at first and then switched to Torco with FM friction modifier and it works much better now and is quieter than the RP. the only thing is you don't need to add modifier if it's already in like RP. i found using slightly less than the 2 oz per fill gives better two wheel burnouts.. you want to use as little as possible and not have "clicking" on turns


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## GTO JUDGE (May 14, 2005)

*The rears are a sealed unit built by Dana. Dana is responsible for the replacements of those. When the rear is replaced, the defective one is sent to GM. GM then sends it back to Dana with a back charge fee. The fee is quite hefty. There is much money to be made in back charge fees for warrantied items. 

The rears can be torn apart and rebuilt, but it is not as easy as one may think. There are strict tolerances in pinions etc that if they are not precise you have..... defects. 
*


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## mtjoy (May 3, 2007)

The tolerances can't be that strict..........look at how much back lash these diffs come from the factory with.....................like svede1212 I've had better luck with torco and their FM than with RP


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## Partsguru1 (May 21, 2007)

I am the Parts Manager at the local Chevy dealership, and we have a tech who owned a 2005 GTO. After he beat the hell out of the car, the rear end started making noise, and we had to replace the whole unit. As I recall, at that time at least, there were no service parts available. Out of curiousity I'll take a look tommorrow and see if that is still the case. I suspect it is though. 

Take care, 

Doug


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## GTO JUDGE (May 14, 2005)

mtjoy said:


> The tolerances can't be that strict..........look at how much back lash these diffs come from the factory with.....................like svede1212 I've had better luck with torco and their FM than with RP


*Incorrect : there IS strict tolerances in the gearing of the pinions etc....,,,,if not there will be slop and play in the gearing.... I used to be involved in building carriers. There is a tolerance level in the aligning of gearing and such. If gearing is out of tolerance there will be issues. *


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## GTO JUDGE (May 14, 2005)

Partsguru1 said:


> I am the Parts Manager at the local Chevy dealership, and we have a tech who owned a 2005 GTO. After he beat the hell out of the car, the rear end started making noise, and we had to replace the whole unit. As I recall, at that time at least, there were no service parts available. Out of curiousity I'll take a look tommorrow and see if that is still the case. I suspect it is though.
> 
> Take care,
> 
> Doug




*There are no parts available because they are Dana parts. Dana receives parts from various vendors. Those vendor parts sometimes have their own part numbers all their own. They are cross referenced with Dana's. You will not find any parts in the rear end with GM parts being the rears are Dana products. They will be DANA parts not GM.*


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## Partsguru1 (May 21, 2007)

Right you are.....I just checked in the catalog and all GM dealers can get are some gaskets and seals. A diff assy is almost $2k dealer cost! Thats just crazy to me, and I see stuff like this all the time. I guess I better hope to keep mine together! 

Doug
'04 W40 6M


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## Partsguru1 (May 21, 2007)

Judge, 

Just an fyi in case you didn't already know this, but GM itself makes very very few of their own parts. They are almost all bid out to vendors. Hence it IS possible for a Dana part to be available thru GM Parts. I suspect in this case regarding rear end parts availability, the clearances are so critical that GM doesn't believe anyone but the original vendor can get it right? 

Doug


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## GTO JUDGE (May 14, 2005)

Partsguru1 said:


> Judge,
> 
> Just an fyi in case you didn't already know this, but GM itself makes very very few of their own parts. They are almost all bid out to vendors. Hence it IS possible for a Dana part to be available thru GM Parts. I suspect in this case regarding rear end parts availability, the clearances are so critical that GM doesn't believe anyone but the original vendor can get it right?
> 
> Doug


*
True.... Dana manufacturers the entire rear. The parts that go into the rear come from other Dana plants, and vendors that produce parts for Dana. Dana makes parts for the auto industry thats their business. GM does buy parts from them as well... Seals from Wix etc.... is Dana parts and other parts will come from Dana owned and subsidiaries. The individual parts and workings of the rear end (carrier) gearing come from Dana's vendors and shipped to their plants from all over. Dana was subbed out to produce the rear end.. The rear end is 1 part that GM purchases, not 200 or so of all the parts it takes to assemble the rear. 

Dana is responsible for the entire rear and every rear replaced comes at a hefty cost to Dana in back charges, labor charges etc from GM. Labor charges can be high maybe 10x the normal cost of labor to assemble them on the line. GM makes out very, very well in the fees they asses Dana. All the internal parts are bar coded and each have their own part number....If you had access to the cross reference numbers and had contacts with the plant that makes the rears you could get the parts. Dana would ship those parts to GM and GM would tag their own part number on it. So yea... the parts can be obtained if you know Dana's part numbers for say the pinions, or the different gears etc. 

As far as GM purchasing the rear end from Dana...... It's a completely sealed unit from Dana carrying 1 part number....... For Dana purchasing the parts to build it.... there are bokoo part numbers in the unit. 

GM, chrylser etc...... use tons of Dana parts... many assume GM makes their own parts.... they make very few. 

As far as assembling the parts "right" GM would do it it right, but not cheaper... Most of Dana used to be union free.... and the labor to do it was cheaper... With Dana all union now I am sure the labor has increased but probably not to GM's wages. 

The Dana plant I worked at... assembled Mack Trucks Axles, Carriers, and Chassis cheaper than Mack could being they are UAW with higher wages etc... The know how to do it right is there, it's just a ton cheaper to farm it out. *


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