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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend> 8" third member swap
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Topic Review (Newest First)
06-22-2006 04:02 PM
blacksunshine Yeah, im not worried about breaking an axle with the lil 302. I hear alot of 9"s have 28 spline axles like the 8"s. I'll just find me a 8" third member with a 3.55 like you said and go from there. Thanks for the help !!
06-22-2006 03:53 PM
xntrik I wouldn't worry about breaking an 8 inch rear until you had 300 hp to the tires, super traction, and were doing severe clutch drops or using a trans brake. Most 8s have the same axles as the light 9s. 8s are getting very popular in the street rod crowd because they are very stout, cheap, and easily available in the popular width, e.g. 70s Granada. $100 wheel to wheel, or $50 or less for the center chunk, unless it is a 70s Traction-Lock which brings $300.. avoid the Equa-Lock if possible..... no parts available.

Grab a 3.50 gear from a mid 66-67 Fairlane OD car, or a 3.55 from a V6 Mustang II. Hope for a Traction Lock differential.
06-16-2006 10:35 AM
onovakind67 The 8" and 9" Ford rears share a lot of common parts. For example, a Granada rear used the same axles, brakes and tubes in the 8" and 9", the only difference is in the center section of the housing. I have replaced 9" Mustang axles with axles from a 8" rear from the same model.
06-16-2006 10:31 AM
Originally Posted by timothale
9's and 9' 3/8 which were used in monster lincolns can be interchanged in a lot of housings with a little grinding but 8's and 9's are different.
Yup, I just read that in that article. This is perfect info. Thanks guys.
06-16-2006 10:23 AM
Originally Posted by blacksunshine this means that the 8" and 9" axle housings are the same?
NO they are COMPLETELY different

Originally Posted by blacksunshine
all I would have to do for a complete 9" rear is swap to a 9" third member and replace my axle's with 31 spline axles?
NO but u could swap the complete rearend out and some should be a direct bolt in. HERE's a good site that'll tell the widths & what kinda car to find a 9" in....joe
06-16-2006 10:21 AM
9 's are bigger

9's and 9' 3/8 which were used in monster lincolns can be interchanged in a lot of housings with a little grinding but 8's and 9's are different.
06-16-2006 09:45 AM
blacksunshine this means that the 8" and 9" axle housings are the same? all I would have to do for a complete 9" rear is swap to a 9" third member and replace my axle's with 31 spline axles?
06-16-2006 08:53 AM
blacksunshine Awsome!! Thanks Joe, thats good info.

Now all I have to do is find a 3rd member w/ a decent ratio.
06-16-2006 08:06 AM
TooMany2count 8inch came in only cars i believe & the dead give away to tell an 8" from a 9" is on the 3rd member the 2 bolts on the very bottom of the 9" u HAVE to use a wrench to remove it. also the eight inch came only in 28 spline

good info on this page about 8" & 9" ford rearends

as for removing its fairly simple. put the car on jackstands, remove ur tires & brake drums. disconnect ur driveshaft, (u might have to disconnect ur brake lines at the wheel cylinder), unbolt the 4 bolts u see on the backing plate, these hold the axle/bearning in. then give the axle a good pull, if it doesnt come out try this. put the brake drum on backwards & tighten up the lugnuts just enuff so the drumm w/still slide on the lugs & then w/the drum as far in as u can get it give it a hard yank. it should act like a slide hammer & pop the axle/bearning out. w/the axles removed start to unbolt the 3rd member, here's a hint:leave 1 or 2 nuts on(but loose) on the top of the 3rd memeber, this way it wont just fall out on u. when all the bolts are off take the top 1 or 2 off & carefully pull the 3rd memeber out. u may have to hit it w/a hammer or use a screwdriver or chisel to break it loose. BUT becarefull when it breaks loose because those thing can & will hurt u ask me i know.
when u put it back together i would replace the seals on the axles & if u dont want to or cant get a 3rd member gasket a good ATV sealer will work just fine. put the 3rd member in the housing, then slide ur axles back in, tighten up the axle bolts, add ur rearend grease, install ur driveshaft, hook up ur brake lines & bleed them(<~~IF u had to disconnect them), & adjust ur brakes & u should be good to go. once the car is in the air i used to do this job in less then hour. normally u'll spend more time jacking the car up & getting ready to do the job & the clean up then u'll have in replacing ur parts..joe
06-16-2006 07:29 AM
8" third member swap

The one thing I know about rear ends is that when they go out and lock up on you, its no fun. This is why I have never touched gear swaps, or any diff for that matter.

But im over my fear of screwing it up and locking the back wheels solid..I have a 69 Torino, just a lil 302 and c4 in it. It has the 8" with a granny 3.00:1 gear, and actually I can still do a burn out, and freeway cruising is at a nice low RPM. I think 3:55's would wake it up just a little bit and not kill my freeway fun. Here's where I need help, if im not mistaken I should be able to pull a 3rd member out of a 3.55:0 ford 8" car / truck and it should be a direct swap right...or should I just look for a complete axle, or maybe a 9" swap. ??

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