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1971 GT
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638 Posts
Discussion Starter · #1 ·
I got the rear end out of the car. I thought it might be worthwhile to flush out the old gear oil from the diff and replace. Can anyone recommend a method for completely flushing and cleaning the gears prior to refilling. I'm willing to remove the cover to get it done. Should I bother or just drain and refill?
 

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Member
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247 Posts
If you are changing all the seals, you may want to consider switching to a synthetic gear oil. If not, and you haven't had a bearing or gears go bad I would pull the cover, clean what I could reach and re-fill.

DAN
 

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Super Moderator
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6,025 Posts
By all means, take the time to flush the differential. I use Varsol in a spray bottle, spray it liberally inside and down the axle shafts, and then drain it out. I have also done the same on transmissions before I rebuilt them. It makes it MUCH tidier to work on without the hypoid oil sticking to everything. And flushing the diff might remove some offending piece of shrapnel that would otherwise prematurely terminate it's life.
 

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Opeler
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3,143 Posts
Varsol and Mineral Spirits

http://www.recochem.com/english/products/household_solvents/varsol.html
Varsol* is great for automotive cleaning to remove oil and grease, and for thinning oil based paints, varnishes and polyurethanes.
* Varsol is a registered trademark of Imperial Oil Limited. Recochem Inc. is a licensee.

Seems to be Canadian product... ?

http://www.recochem.com/cdnav/cdprohsfaq.htm
Q: What is the difference between Mineral Spirits and Paint Thinner? What other names is it known by?

A: Mineral Spirits has fewer aromatic solvents while other similar products - Paint Thinner, Varsol® - contain higher concentrations. All are petroleum distillates.

Q: What is the difference between Varsol® and regular Paint Thinner?

A: Regular Paint Thinner is a "generic" brand of thinner while Varsol® carries a guarantee of purity. As a result, Paint Thinner is usually less expensive than Varsol® but can be used for many of the same applications.
 

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Member
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1,735 Posts
I would recommend that you stay with standard diff. fluid , pull the cover clean & inspect , also clean the vent . Then drive :D
 

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Premium Member
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1,973 Posts
the diferential is completely out of the car and there were some fine metal flakes in it so I will be flushing it one way or another. Then would paint thinner be fine? diesel fuel?
 

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Super Moderator
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6,025 Posts
I didn't realize that Varsol was a Canadian thing. Imperial Oil is "Esso" here, which you might know as Exxon. But in any event, any decent non-volatile de-greasing solvent such as Gunk or even paint thinner (sub-terps, aka turpentine) should be fine .
 

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Premium Member
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Would I have to gut the differential first to do this? (bad idea) or just try to get as most thinner out as humanly possible?
 

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Senior Contributor
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5,083 Posts
Jordan,
I would not disassemble the rear if you don't have to, flush it the best you can, then if you are concerned about residual thinner, fill drain and refill, that should take care of any pockets of solvent, matter of fact, better to fill, drive for a couple of miles, then drain and refill.
 

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Opeler
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3,143 Posts
Differential fluid drain plug (bolt) ...

Removal of bottom, center bolt on differential cover allows lubricant to drain.

After cleaning differential "insides" with appropriate solvent of choice, leave rear cover off for several hours (or overnight) to allow cleaning vapors to evaporate.
 

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Paul and Amanda Opelers
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64 Posts
Removal of bottom, center bolt on differential cover allows lubricant to drain.

After cleaning differential "insides" with appropriate solvent of choice, leave rear cover off for several hours (or overnight) to allow cleaning vapors to evaporate.
Hmmm - what is the easiest way to FILL said GT differential once drained and cleaned?? I don't think there's a fill plug - or did I miss one on my 73?

Thanks!

Paul S.
Flagstaff AZ
 

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1971 GT
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638 Posts
Discussion Starter · #13 ·
Hmmm - what is the easiest way to FILL said GT differential once drained and cleaned?? I don't think there's a fill plug - or did I miss one on my 73?

Thanks!

Paul S.
Flagstaff AZ
I'd say you missed it. There is a fill plug that normally takes a hex driver. If my memory is correct, it's on the upper right of the cover.
 

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Old Opeler
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5,564 Posts
Flamable!

I would not put anything more flammable than Diesel or perhaps Kero into a diff to clean it.
Best to just take the back cover off and use a diesel soaked brush to sweep the debris out of the bottom of the housing. Any greater 'flushing' is just as likely to distribute debris around and into the bearings - making things worse!
If there are lots of chips and flakes in there, the diff is 'on the way out' any way.
 
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