Differential question

[historyg]

hey i was wondering if i could just buy a Differential and put it into my rear axle assembly, would that work like im looking at this
http://www.summitracing.com/parts/PWT-9 ... mage=large

would that allow me to use my stock rear end, instead of looking for a grand national or 442 rear end, if I am wrong I am sorry, i am just not sure...

Thanks

 

[pontiacgp]

:?

 

[Bonnewagon]

I did just that to my 83' Bonnewagon. It has a 301 4-speed manual so the 7.5 rear is quite strong enough. I scored a rebuilt 7.5 posi setup at E-town swap meet for $200.00 and installed it in one day. You don't even need to touch the pinion gear. Just swap over the ring gear onto the posi and reinstall it using a new shim kit. Just record the initial backlash and tooth contact pattern so you can put it back the way it was.

 

[historyg]

thanks guys so if i bought this instead

http://www.summitracing.com/parts/ETN-19663-010/

or something similar would it bolt in or, would i still need a new housing, the housing on gbodyparts.com for 950 does it come with everything? I am just so confused with this rear end, I am just so new to it. is it just pretty much a housing for the differential and axles, and the that's it, or is it made up of more.

Would i be better off with a 8.5, does it perform better then the 7.5?

Thanks again and sorry for the questions over and over again.

 

[Bonnewagon]

Are you pushing serious horsepower? If so an 8.5 would be great or a Currie Ford 9 inch that is set up for your body though these are some serious money too. The Eaton is a very good unit and rebuildable.Prices seem to be dropping on the G/N 8.5 rears I saw one at E-town with 3:42 posi going for $600.00. If you are not fluent in setting up rears a whole complete rear would be your best bet. Just bolt it in with new bushings and go. A buddy just had 3:73 gears installed and it was hard to find a shop capable of doing the job these days. For a stock low HP motor you might get lucky with a junkyard or swap meet posi rear.

 

[pontiacgp]

:?

 

[historyg]

i am going for around 400 hp with a fully built sbc 350 or a olds 350 , I want to do the whole suspension, and drop the rear axle assembly and bolt in a new one, but it seems it might be a lot harder then i thought. if the 8.5 is 950 on gbodyparts.com i might go with that as it seems to be the cheapest route

 

[Bonnewagon]

What you want to do is easy-just drop in a new rear. Boxed or adjustable tubular control arms. Poly or aluminum bushings. With 400hp I'd go with the complete 8.5 assembly which is basically a 70's Camaro/Firebird rear adapted to the A/G body. I have a GM ring and pinion gear tool and even with that I scratch my head and cuss every time I do a rear. As stated above the new pinion shim is usually within .001 or .002 of the one GM put there. It's the backlash and preload that guys mess up.Pro's just go by tooth contact pattern,but I'm no pro! If you have not digested the GM service manual instructions on ring and pinion servicing I'd advise not touching it. Just get a new rear.

 

[pontiacgp]

:?

 

[Bonnewagon]

Actually the preload is quite important on the ring gear carrier just as it is on the pinion. The slip on test bearing is a great way to perform the pinion depth operation but if you have the depth setting tool it uses no shim at all at first. The tool measures the pinion depth in relation to the centerline of the axles. A fixture mounts where the carrier bearings would go and you measure away.Using an existing shim in a pinch is acceptable since most of the time the original GM shim is right on with very little variation between pinion gears has been found in my experience.A plus (+) or minus (-) stamped on the gear warns you to add or subtract accordingly.Once the depth is verified,then the pinion crush collar is carefully tightened to establish the pinion preload as measued with a torque wrench on the pinion nut. Carrier preload consists of installing the carrier and bearings to a 0" clearance and then adding .008" shims (.004" on each side)to preload the bearings. The proper way is to get an initial clearance of ,say, .010" and then knowing that adding .018" will achieve the proper preload. Then the backlash is checked and corrected by adding or subtracting shims equally from either side thus moving the carrier closer to, or farther from the pinion while maintaining the preload. Once the backlash is correct,tooth contact pattern is checked with dyed oil to verify that the pinion and ring gear are meshing correctly,patterns being different for new vs. used gears. Seems like a lot of work but remember that the gear set is held in place very tightly thanks to the preloads and allows the gears to operate properly under extreme loads without moving and letting the gear mesh change.I've done gears with a feeler gauge and luck, and got away with it, but I've also trashed gears that way. Once you learn to do it as per the GM service manual,you are rewarded with quiet long lasting rear ends that you can forget about. Then all your friends want you to do their rears. Sorry for the long winded post but it is a complicated operation.