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Rear Differential Leaking


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My rear differential is leaking going to take it to the transmission shop to get it looked at. Not too familiar with rear differentials. Anybody out there who can give me some education on why they usually leak, what to look for , what seals usually need to be replaced etc. and what is a reasonable cost to replace the seals etc. so it stops leaking.

 

Thanks

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My rear differential is leaking going to take it to the transmission shop to get it looked at. Not too familiar with rear differentials. Anybody out there who can give me some education on why they usually leak, what to look for , what seals usually need to be replaced etc. and what is a reasonable cost to replace the seals etc. so it stops leaking.

 

Thanks

 

4 opportunities to leak. 2 axle seals, pinion seal and main pumpkin seal. If it is leaking at the pinion, make sure there is no play in the pinion shaft and bearing that may cause seal wear. Axle seals require a press, so a auto shop is right for that.

 

kcmash

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You need to be cautious with pinion seal replacement. Lots of people just remove the pinion nut with an impact, pull the yoke, pry out the old seal, drive in a new seal, install the yoke and nut then tighten the daylights out of it with an impact.

 

That is a disaster waiting to happen with any rear end with a pinion bearing crush sleeve(like a 9"). There are two different ways pinion bearing preload is set. First way is with shims between the two inner opposing bearing races, most Dana axles are this type, the second is with a crush sleeve between the two opposing bearing races. With the crush sleeve type the more you tighten the pinion nut the more pinion bearing preload you have. Too little or too much bearing preload spells bearing failure. With a shim style setup pinion seal replacement is easy, because tightening the pinion nut after seal replacement does not change preload. Changing a seal on a crush sleeve setup is a real pain. First you should pull the whole pinion assembly out of the front of the 9" 3rd member, then get a dial inch pound torque wrench and see how many inch pounds it takes to turn your pinion. After you record that remove the pinion nut and yoke. Next replace the seal, then install the yoke and pinion nut. Then it gets tricky, you want to tighten the pinion nut until the torque it takes to turn the pinion is a few inch pounds higher then when you took it apart. If you screw up and go too far you have to pull the whole assembly apart, install a new crush sleeve and try again.

 

So many mechanics don't understand this and end up destroying pinion bearings. Stock 9" axles have crush sleeve type pinion preload setup.

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How about the costs to place the gaskets?

 

 

 

 

You need to be cautious with pinion seal replacement. Lots of people just remove the pinion nut with an impact, pull the yoke, pry out the old seal, drive in a new seal, install the yoke and nut then tighten the daylights out of it with an impact.

 

That is a disaster waiting to happen with any rear end with a pinion bearing crush sleeve(like a 9"). There are two different ways pinion bearing preload is set. First way is with shims between the two inner opposing bearing races, most Dana axles are this type, the second is with a crush sleeve between the two opposing bearing races. With the crush sleeve type the more you tighten the pinion nut the more pinion bearing preload you have. Too little or too much bearing preload spells bearing failure. With a shim style setup pinion seal replacement is easy, because tightening the pinion nut after seal replacement does not change preload. Changing a seal on a crush sleeve setup is a real pain. First you should pull the whole pinion assembly out of the front of the 9" 3rd member, then get a dial inch pound torque wrench and see how many inch pounds it takes to turn your pinion. After you record that remove the pinion nut and yoke. Next replace the seal, then install the yoke and pinion nut. Then it gets tricky, you want to tighten the pinion nut until the torque it takes to turn the pinion is a few inch pounds higher then when you took it apart. If you screw up and go too far you have to pull the whole assembly apart, install a new crush sleeve and try again.

 

So many mechanics don't understand this and end up destroying pinion bearings. Stock 9" axles have crush sleeve type pinion preload setup.

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I believe the factory service manual outlines the procedure for replacing the seal without installing a new crush sleeve. I don't have it handy but essentially you remove the yoke, r&r the seal and reinstall the yoke with a new nut and torque to 125 ft/lbs.

 

I have done this successfully twice and unsuccessfully once.:-/

 

To me for the cost of a seal and nut it is worth a shot.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.

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My open 3:00 9" was leaking at the pinion seal. I figured it was a good time to switch over to a 3:50 posi. I tried to keep costs down, so I bought used ring and pinion gears and a rebuilt traction loc. Since I needed a shop to press on the new pinion bearing, I had them do axle bearings. Plus the bearing/gasket kit. Plus the lube and friction modifier. Plus, plus, plus... So much for keeping costs down - LOL! It was an expensive endeavor!

 

The whole job was an expensive PIA, but I love the new gears!

1973 Mach 1 Q-code C6 3:50

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How about the costs to place the gaskets?

 

 

 

 

You need to be cautious with pinion seal replacement. Lots of people just remove the pinion nut with an impact, pull the yoke, pry out the old seal, drive in a new seal, install the yoke and nut then tighten the daylights out of it with an impact.

 

That is a disaster waiting to happen with any rear end with a pinion bearing crush sleeve(like a 9"). There are two different ways pinion bearing preload is set. First way is with shims between the two inner opposing bearing races, most Dana axles are this type, the second is with a crush sleeve between the two opposing bearing races. With the crush sleeve type the more you tighten the pinion nut the more pinion bearing preload you have. Too little or too much bearing preload spells bearing failure. With a shim style setup pinion seal replacement is easy, because tightening the pinion nut after seal replacement does not change preload. Changing a seal on a crush sleeve setup is a real pain. First you should pull the whole pinion assembly out of the front of the 9" 3rd member, then get a dial inch pound torque wrench and see how many inch pounds it takes to turn your pinion. After you record that remove the pinion nut and yoke. Next replace the seal, then install the yoke and pinion nut. Then it gets tricky, you want to tighten the pinion nut until the torque it takes to turn the pinion is a few inch pounds higher then when you took it apart. If you screw up and go too far you have to pull the whole assembly apart, install a new crush sleeve and try again.

 

So many mechanics don't understand this and end up destroying pinion bearings. Stock 9" axles have crush sleeve type pinion preload setup.

 

 

You lost me.

 

Place the gaskets?

 

The gaskets on a 9" are pretty easy to replace. Just remove 8 bolts and slide out the axle shafts, then remove the 10 nuts that hold the 3rd member in. Replace gaskets and slap it back together. Maybe a few hours worth of labor if the shop has a lift?

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The gaskets on a 9" are pretty easy to replace. Just remove 8 bolts and slide out the axle shafts, then remove the 10 nuts that hold the 3rd member in. Replace gaskets and slap it back together. Maybe a few hours worth of labor if the shop has a lift?

 

That's why they call Ford 9" axles drop out differentials. ;) :D

Eric

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Did this on 2 9" rear ends two weeks ago with a buddy as we were changing ratios in his car and resetting backlash in mine after changing pinion bearings. With two of us working at a relaxed pace it took us nine hours, but we also built most of one center section in between.

 

5 hours labor or less, parts are about 50-75 bucks with fresh lube.

 

and you do not need a press to do axle seals.

 

Nifty trick for pulling axles I will share Take a nylon strap tie it into a loop about 2 feet long, wrap it around the axle when you are ready to pull twice so that the loop opens with one strap directly across the flange from the other Pull it away from the car with one hand and take a heavy hammer and hit the strap on the inside a few times and the axle will pop right out.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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another issue that is overlooked when servicing rear ends;

 

if you have a lapped set of gears or not.

 

some factory gear sets are lapped, they have paint marks that have to line up when assembled.

 

most trans places don't even know about that, so they screw up the preload on the bearings and then miss assemble the gear set by not aligning the paint marks on the teeth.

 

you don't know if you have a lapped set until you take it apart. so if you don't have a lapped gear set and you need to fix the front seal on the pinion then you have a pretty easy job. you can pull the nose off change the seal and re-torque the pinion bearing preload with a new crush sleeve. then reassemble no problem....

 

if you have a lapped set then the entire pumpkin has to come out removing the rear brakes and pulling the axles which will need new brake backing plate seals. it is much more work. all this because when you reassemble you need to be 100% sure you lined up the paint marks on the gear face.

so a simple seal replacement is not so simple.

 

truth is when the seal is leaking then you want to look at the rest of the diff anyway you already have to service the diff might as well go further.

 

90% of the trans places are criminally bad, because my trans and 3rd member was rebuilt by the worst trans place in NY i eventually had to rebuild my entire rear axle myself and rebuild a new transmission myself and chunk my old C6 in the trash.

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