help swapping 8 3/4 center chunk?

[kenicb]

Hey there could someone please give me a step by step on making this swap.

I have a complete 8 3/4 center chunk with 742 housing 3.91 gears
The car currently has an 8 3/4 with 741 housing and 2.76 gears

I'm unsure how to slide the axles out. How far? will i need to replace any seals or anything?

How will i know how to align the axels with the new center chunk? Is it a feel thing or Will it all just line up when i slide them back in?

a step by step would help me a bunch. Thanks God Bless

Keni


www.kenithomas.com

 

[68bee70rr]

Its very easy, you only have to pull axles out enough to be able to pull center chunk (pumpkin) out. You should replace your gaskets on your axles, so pull them all the way out to replace gaskets. Auto Zone and most other parts stores still has them available or can get them for you in a day or two. When your putting the center chunk (pumpkin) back in also get a gasket from your local parts store. Make sure you have an extra set of hands because of the weight , it can be hard to do by yourself but i have done it. When sliding axles back in you may have to slightly wiggle them a little to get them back in. No big deal really. Dont forget, besides your regular gear lube to get the Posi Additive for posi units or you will burn yours up. I hope this helps.

 

[5.7 hemi]

Also dont forget to re-set the axle end play if you are still using the factory style Timken bearings, green bearings just re-install the axles.

 

[eagleone1983]

Dont forget, besides your regular gear lube to get the Posi Additive for posi units or you will burn yours up. I hope this helps.

Some brands already have this additive in it and do not require it. I've got the Lucas stuff and it says right on the bottle "No additives required" I confimed this with the guy that build my diff

 

[dryheat]

Also ... while you have it apart you may want to replace the axle bearings too ... depending upon their age/condition and your budget of course.

 

[racedodge]

you really do not need a gasket for the differential itself, black RTV works just fine. I have found when people use gaskets they usually split them by tightening down the nuts too much thus causing a leak. factory never used gaskets for the rear diff.

now, with that being said.. getting to your axles. they can be pulled out without removing all of your rear brake hardware, just be weary of the lever between the two brake shoes... you can lift it up a smidge to pull your axle out.

I would pull your axles all the way out so they do not rest on your inner axle seal. this weight can cause a split in the seal thus causing a leak. speaking of which, it is a great time to inspect that seal while the axle is out to determine if it needs replacing. if it is the OE seal, then replace it.

step by step:

1. loosen lug nuts
2. jack up rear end of car and place on jack stands
3. remove rear wheels
4. remove brake drums
5. remove the 5 nuts that hold the axle flange
6. lift up brake drum lever that resides between the two brake shoes, and pull the axle from the axle housing ensuring that you do not put any pressure on the inner seal
7. inspect inner seal for premature wear, remove and replace if it is the OEM seal
8. remove driveshaft
9. loosen and remove each nut on the differential carrier
10. place a drip pan underneath the differential carrier
11. use a screwdriver and a hammer and pry the bottom of the carrier away from the housing to drain any and all fluid
12. once fluid has been drained, remove pan and use a floor jack with a board and place under the carrier and pry carrier away from housing so that it will be supported by the floor jack
13. clean out any old fluid in the axle housing with papertowels
14. with a razor blade or your preferred method, begin to remove any old silicone in between the studs on the differential, ensuring surface area is clean of any contaminates
15. apply a decent coat black RTV in between and around studs (attempting to veer away from getting to close to differential opening on housing)
16. install new differential carrier using your manly muscles or a floorjack
17. replace all differential nuts to studs and tighten in a star/opposite pattern (I use nylon thread lock nuts)
18. replace axle's in reverse steps as above
19. let silicone set for a minimum of 12 hours prior installing fluid
20. 12 hours later add your gear oil through your brake vent bolt hole or on the side of the carrier (seen it done both ways).
21. start up car and put in gear and let wheels turn to get fluid flowing throughout the entire housing before putting a load on it.
22. let car off of jackstands and start driving it

 

[roadrunnerh]

Excellent step by step racedodge. I would add one little option.

In step 9, remove all the nuts completely except for the top two, keep those two on by just a couple threads so you can pry the carrier without risking it falling out and making a huge mess. Once it's drained, remove those two nuts.

 

[65 Dartman]

7. inspect inner seal for premature wear, remove and replace if it is the OEM seal

What are you guys using to drive the seal in if you don't have a seal driver (or correct size)?

In till it won't go any further?

 

[racedodge]

What are you guys using to drive the seal in if you don't have a seal driver (or correct size)?

In till it won't go any further?

if you do not have a seal driver, you could knock it into place using a 2lb mallet and a 2x2 piece of wood alternating with each strike, but doing it so you do not contort the seal. I have done it this way in the past and just took my time. I drove it until it is fully seated and called it good. You have to get it fully seated, if you do not, then the bearings (either tapered or green bearings) will obstruct your ability of fully seating the axle into the carrier.

 

[65 Dartman]

Thanks for the info!

 

[kenicb]

Hey RaceDodge, thank you so much for taking the time to write me out the step by steps. Using your guide, i got up to step 14. begin to remove any old silicone
I've already ordered the differential gasket and the two gasket-seals for ea axle so Im waiting on those to arrive.

But you can see where Im at so far. the new 742/ w 3.91 is the one on the left. The 741 w 2.76 is the original on the right w the yellow on the gears. Will keep you posted. Thanks again. Godspeed

keni

a close up of the adjuster ring to take out the end play. notice the little locking device that holds it in place.

 

[racedodge]

looking good! keep up the good work. if you want to use the carrier diff gasket you can, but 1/8" bead of RTV silicone works just as good.

way to git'er done!