Rookie differential question

[jreyes]

Hi have a 9" rear end in my 72 F100, and a friend has a 8.8" rear end from 1990 Grand Marquis with posi trac for sale..

Question is if I can use the posi track in my 9" rear end with out changing my axels bold pattern?

if not, what will be batter to look for with out spending much money?

thanks

[clemsonjeep]

Not sure what you're after here but you cannot use a position from an 8.8 in a 9". You could swap the entire housing into your truck but it is wider and a different wheel bolt pattern.

[tnlprt]

In a word

No

Cheapest way is to weld the spider gears .....DONT DO IT

next cheapest way is to shim the side spider gears tighter.....Wont last long

next you could put a mini spool in ....Not recommended for the street

Full spool......Also not recommended for the street

Traction loc.What ford used in most vehicles.....Put any kind of heavy load or big tires on it and it will fail

Detroit Locker.....Noisy but works very well

Look for 6 cylinder 4 wheel drive trucks for traction locs .....Not all but a lot of those trucks have them
They may also be 31 spline axles which you should have 28 spline axles

[motzingg]

Yeah i'm in the same boat and have done the research on this.

Almost every axle post-bumpside got wider by at least 2" on either side. Swapping in a later model axle is easily the cheapest solution to getting a posi because the axle can usually be bought for less than it would cost to even buy the bearings and seals to rebuild the old axle.

Dentside axles, up until switching to 8.8, are 32 spline and 2" wider on each side. The springs are wider (2.5") and the perches are in a different location. The most direct way to swap would be to cut off all the old perches (very carefully) and weld them on to the new axle, keeping your entire geometry the same. You could probably even weld the old perches on the new axle without cutting off the new axle's OG perches, using a plate to keep them positioned correctly.

The panther axle is probably coil sprung? just guessing... no idea what to do there.. i guess cut everything off in that case, and try to get your leaf perches welded on somehow.

I don't know a ton about the 8.8 rears but the panther cars will be 5 on 5 instead of 5 on 5.5" bolt spacing. Once again, not a huge deal, but it is something to consider.

The u-joint might also be different, the f-150's of that era are the next bigger size, cant remember if its 1310-1330 or what exactly.

Hmm... what else?


So yeah, short answer, no the 3rd member wont swap... bummer. The 3'rd wont even swap from a Dent or a Slant, which in my area are pretty easy to find with posi 9" ers.

To make matters worse, the narrow rear end from a bumpside is what all the mustang guys are looking for to swap in, so they are priced way up at any swap meet or on craigslist. Bummer. The plus side to that is if you do swap your axle out, you might be able to sell it for 300-400 bucks, based on what i've seen them listed for. The Posi ones i've seen for sale 500+

[ultraranger]

All Ford F100s with a 9-inch rear end before 1973 had 28-spline axles. The only pre-'73 F100s that had 31-spline axles were the '68-'72 F100s that had a Ford 9-3/8" rear end. --I have 31-spline axles, in my stock '69 F100 9-inch rear end housing, that came from a '71 F100 that had a 9-3/8" rear end. My 3rd member is a Ford 9-inch N-case with a 31-spline Traction-Lok and 3.50 gears that came from a '75 F150 4x4 9-inch rear end.

My stock '69 C7AW-E casting 9-inch single vertical rib 3rd member with 28-spline open (single track) differential and 3.50 gears.



'69 9-inch 3rd member on left compared to the factory '75 Daytona 9-inch N-case on the right.



N-case installed in my truck's '69 9-inch housing.



My stock F100 28-spline 9-inch rear end axle on the left, '71 F100 31-spline 9-3/8" axle on the right.



'71 F100 9-3/8" 31-spline axle installed in the stock '69 F100 9-inch rear end housing.




Any 9-inch 3rd member will fit any 9-inch rear end housing (car or truck). The catch is the spline count of the differential has to match the spline count of the axles.

The widest (optional) 9-inch rear end used in the early Mustangs was in the '71-'73 models. All early Mustang rear ends had small axle bearings and a lug pattern of 5-on-4.5". The '71-'73 Mustang rears are the same overall bare housing width (56" wide, w/no axles & no brakes installed) as the Bumpside trucks but, the housing is not configured the same as a Bumpside but, also goes back to different sized axle bearing, lug patterns and size of brakes.

Bumpsides have equal length axle tubes and axles on both sides. Early Mustangs have a short side axle/axle tube on the left and a long side axle/axle tube on the right.

MOST '73-'79 9-inch rears have 31-spline differentials and axles. SOME '73-'79s have 28-spline differentials and axles.

1980-1986 9-inch rear ends all had 31-spline axles. Some '80-'83 Ford 9-inch rears had a 5-on-4.5" lug pattern compared to the rest that had a 5.5" lug pattern.

8.8" rear end was first optionally available in the F100/F150 trucks in 1983.

The Ford limited slip differential first came out in 1957. It was known as the Equa-Lok and was in use through 1968. In '1969, Ford revised the differential with a much better design --it's known as the Traction-Lok. It was also optionally available through 1986.

The Traction-Lok differential, for a Ford 9-inch rear, isn't the same as the Traction-Lok differential in a Ford 8.8" rear end (differential can't be swapped between the two rear end types).

[Grease Monkey]

I'm looking at this to cure my one wheel peel...........http://www.summitracing.com/parts/sum-c ... /make/ford