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Author Topic:   8.5in rear
btennant
Dirt Full Roller

Total posts: 28
posted August 01, 2005 06:03 PM  
Do you think it would be feasible to run an 8.5 gm rearend out of a B-body in a G-body? I have one out of a 96 Imp with rear disc brakes and was thinking of using it to move up next year. I know it will take the abuse my drag car (B-body) makes 600 ponies on the bottle and the stock rear end with a few mods has yet to fail me. The only real difference is width. And would that really hurt you out back? Maybe just different offsets on the rear wheels would help.

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 01, 2005 07:43 PM  
I think you're backwards - G-bodies aren't "big metrics" - they are 108" wheelbase (Cutlass/Regal/MC/Grand Prix). A b-body is 116" wheelbase (Impala/Caprice/LeSabre/88/etc).

YAZ
Dirt Maniac

Total posts: 147
posted August 02, 2005 08:43 PM  
If your rules make you run a gm rear end,
Then I would use the 8.5". the axles are
bigger than the 7.5"
I ran the 8.5 four years and never broke
one.

but if you can run the 9" ford, thats better yet.

outlaw#03
Dirt Roller

Total posts: 25
posted August 03, 2005 11:33 AM  
You can put an 8.5" out of a "big" car in a metric car but if you can go with a Ford 9". The 8.5" is 4" wider and the upper trailing arm mounts are at different angles. You can run offset wheels in the back (which is a pain in the **** ) or narrow the 8.5". To overcome the upper trailing arm angle problem you can cut the upper trailing arms down about 1 1/2" or cut holes in the frame at the mounts and relocate the arm further forward.

An easier fix is to put 28 spline axles from Moser www.moserengineering.com in the 7.5".

Just order axles for a 7.5" rear end with 28 spline ends and weld the 28 spline side gears out of an 8.5" rear end. You’ll have to grind flat spots on the C-lock holder pin and your done.

Koolaid
Dirt Forum Racer

Total posts: 82
posted August 03, 2005 03:10 PM  
I'm confused why you would want to order Moser's with 28 splines and go through that work to put them in a 7.5" rearend? The 26 spline Moser's will go right in and I haven't heard of people ruining axles at the splines - sounds like everything stock busts out by the hub. Maybe I'm missing something - I'm new to the whole racing thing this year.

Also - would someone explain to me why a non-full floater 9" is a good choice? I've always had Ford street vehicles and am familar with it - I put a lot more trust in a c-clip holding up to a shear load then just the interference fit of a bearing pressed onto an axle? It seems like with enough bumps and knocks the 9" axle can start working it's way out the side of the car (and I have seen a couple of Ford's with non-full floaters do this at the track). If I have a C-clip style setup with strong axles with good c-clip grooves and c-clips that aren't hammered to death I don't think they'll just up and shear off on me? I'm not trying to start an argument or anything - just hoping someone with more knowledge on this subject will lend me some advice. Thanks.

wenee9w
Dirt Roller

Total posts: 11
posted August 03, 2005 03:23 PM  
The retainer that holds the bearing on can be tack welded to the axle to make a po-mans floater.If the axle breaks the wheel will remain with the car.To a certain degree.

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 03, 2005 04:42 PM  
Thats just the thing I was planning to move up to the street stock class with bigger motors and bigger tires and more bite. And yes most if not all of the street stocks run a fud 9inch but i just wanted to be different. also if the upper control arms are different on the B-Body (as in big car thats how I remember)what do you do to the 9inch to get the uppers yo work? How about a 8.5 out of a camaro firebird 2nd gen (70 to 81) cut off the leaf spring perches add lower control arm mounts coil spring mounts and a plate across the top of the carrier for the upper control arms? Hate to keep askin but I like my gm all gm and do not doubt the generals engineering to put the power to the ground. Speed kills drive a ford live forever

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 03, 2005 09:12 PM  
BIG CHECK??? You mean you guys get a check if you win? must be nice lol. I win.....That just means I get a bigger mug then second and third and it sayd feature winner. I'm running a 8.5 out of a 75 monte in my 81 cutlass metric chassis.....and I have no problem running in the top 2 every race. My cars a definate winner with the 8.5, but then again we can run a 9 inch in our class so I'm limited. But if we were given the option right now to run the 9 inch....I would stay with my 8.5 GM. But then again I am different too....and winning being different is the added bonus lol. Anyways mine is dialed in using the 8.5, so me going to a 9 inch wouldnt work cuz then its all the work to get it dialed in again. If I was running multiple tracks and can run a 9, I would change it then so gear changes from track to track would be easier. Maybe I'm the wrong guy to ask about rears....cuz I'm happy with what I have.....but under other circumstances would change to the "F" word rear lol.

outlaw#03
Dirt Roller

Total posts: 25
posted August 04, 2005 11:36 AM  
I put the 28 spline axle in because 90% of the time the 26 spline axles break off at the splines, very rearly do we break them at the flange. By putting the 28 spline axles in the 7.5 you can take advanage of the lower rotating mass of the 7.5 compared to the 8.5 (not a big help for a bomber but can't hurt) I'm running pretty close to 375HP and have never torn up a 7.5 carrier but have broke many, many 26 spline axles. Just my $.02.

btennant
Dirt Full Roller

Total posts: 28
posted August 04, 2005 03:02 PM  
Still didnt answer my question on how to hook up a ford rearend in a gm G-body. Is it a direct bolt in from another car? What i was refering to on the upper control arm mounts on the 8.5 F-body rear end is a plate that hooks to the axle tubes and crosses over the top of the housing. I know u cant weld steel to cast. Dude 75 monte rear end is it a direct bolt in? That would be cool.

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted August 04, 2005 04:17 PM  
Yes it pretty much is a direct bolt in. The upper control arms have to have there hole drilled 1 1/4" farther forward and you have to weld bolts to the back of the lower control arm bracket for your shock mounts....being the monte has the shocks mounted on the front side of the rearend. The spring perches are mount off center towards the back so the springs sit angled back on the bottom....but just a little bit...not to much.....I left mine like that but you could cut the perches of the 7.5 and weld them to the 8.5 if you were concerned about it. I left mine and it doesnt make a difference. Also the flexable brake line has to be taken loose off of the frame and let it hang....you could make a braket for it....but I just let mine hang. Also use the flexable line for the 8.5.....not the one from the 7.5. Its super simple....I put the gears in my 8.5 and welded up the spiders the pulled the 7.5 out and put the 8.5 in and it only took me 1 1/2 hours to do it....and thats taking a couple beer breaks too. If you want more info on it or have any questions just PM me.

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 04, 2005 07:46 PM  
are you talking stock or good hardened axles?i'm still not getting where 2 more splines does anything for you?the axle is still the same diameter. if the splines were a big deal you wouldn't see anybody running 28 spline fords just 31's. your lower rotating weight is countered by running the tranny in 2nd or low gear instead of the 1-1 high gear you can run with fords. yes i supose if you are only planning on running one track your entire carrier and have the right gear then stick with your gm but with the way they change rules on tires and motors now a days you may need to change gear that you can't get in a gm you can't get anythinjmg between a 3.73 and a 4.11 in 7.5 alot of times it's pretty tough to get geared with a new tire you may have to run where with a ford you have 5,43,5.67,5.83,6.0,6.20. like with mine we have to keep the gm in my class and if they went to say an 85 in spec tire i would be screwed i could either run a 5.67 or a 6.24. one is way to little the other is way to much

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