Upgrading 7.5 to a 4.10/4.56

[Garage Hound]

Guys (and gals),
I am going to remove the stock 7.5" rear from my '80 Malibu this winter and upgrade the r/p to a 4.10, possibly a 4.56, gear ratio (4.56 scares me a little with my 355 SB/TH350 combo). I will probably install a new pair of axles as well. My question is this, what else can I do, cheaply, to get some strength/safety out of this thing. I was thinking about eliminating the C-clips, but I am not sure how that is done. I can't afford a complete rearend right now, and I hate the car sitting idle on the trailer all the time (strip use only). I puked up the TC last year because I was pulling the car through the traps in 2nd gear due to the stock rear ratio. After $750 in damage control, I didn't run it much this year hoping a cheap rearend would come along before I could tear things up again. Unfortunately, one didn't. I am probably pushing out 425-450 HP. Any ideas? Just trying to save money, while trying to make ET. Thanks in advance.

Jay

 

[DOUG213XRJ]

Replace all the bearings and seal.

 

[406Elcamino]

you could weld the tubes of the axles and get a T/A support cover the covers ties in the caps so they dont walk probably better off doing that then investing in c-clip elims in a 7.5" anways

those 7.5" are hit or miss though we through a cheapo 411 gov lock rear together my brother beat that thing pretty badly with the ol 283, i had it behind my 406 that makes brutal torque and not once did it ever give me problems and then this year my brother had it back in his car with his blown355 and a m21 which slicks and clutch dumps that thing still didn;t blow!

 

[79malibusbc]

you should really think about upgrading the rear totally to a 8.5 or 12 bolt or ford 9" if you can afford it.. i found tihs i dont know how far it is from you but here ya go

http://www.maliburacing.com/forum/viewtopic.php?f=10&t=74752


btw that is a steal

 

[Garage Hound]

Yeah, I really would like to upgrade, but I have looked for a long time for a bolt-in 4.11 or 4.56 within my budget ($400) and cannot find one. I usually look on craigslist in my area, but with no luck so far. That's why I thought I would do it myself. I have heard differing opinions about the strength of the 7.5", so I guess it will just come down to luck how long it holds together. If I blow it up, I can always get a part-time job long enough to pay for an awesome new rear. I don't suppose that was included in the bailout plan, huh? No, I didn't think so. Where I come from, you have work to make a living, and actually pay for your toys.

 

[79malibusbc]

i agree with you 100% but do you want to just waste $400 bucks...putting money in the 7.5 is just like throwing your hard earned money in the wind just to say goodbye to it.. did you think about doing a early chevelle 8.2 rear like a 68-72 there out there and very cheap..if you get that its a whole lot stonger then the 7.5.... my just my 2cents

 

[monzaz]

No 10 bolt 8.2...please. they have a smaller pinion shaft then the 7.5...lol. TRUELY.

I can help with the 7.5 rear parts BUT as stated before you should save your money and put it into a 10 bolt 8.5 . I have one of thwe guys on this board making up upper control arms for my custom 8.5 replacement rears COMING with in the month. they are made from the 1973-1977 center sections and the lower and spring perches shock mounting locations will all be stock location. The uppers will be fully adjustable for many different pinion angles. They will be in a realistic price range NOT a strange or moser price range. hopefully a complete posi rear will be under 1000.00. stock brakes shocks control arms (lower ) will all be usable. Driveshaft will still need the same 3/4 to 1" shortening...But that was with the 10 bolt 8.5 gn rear too. Same deal. All new stuff in the guts. Look for it soon. Jim

 

[Mike Allred]

I tried to get a 7.5 to live behind a mild 283 that ran low 8s in the eighth and in a year broke 2 mini spools, one ring and pinion, and two axles. Everything about them is weak. They're a grenade. The car had a TH350, loose 4,500 converter and a 4.56 7.5 gear. 12 bolt is in there now with the good stuff and believe me, I could now kick myself for throwing $800 plus into the 7.5. Truly wasted $.

 

[monzaz]

If you are truely just racing the car.... Any thing over 3000 stall I consider. It is foolish to even think about the 7.5 rear. Unless your trying to prove some wacky point to the world.
I made a 10 bolt 7.5 go into the 11.90 range but that was with 2500 stall and a screaming motor. Not a heavy launch and it was in a Monza. But remember the monza stock pinion is an even smaller diameter than the standard 7.5 1.438 compared to the 1.375 of the Monza pinion shaft. lol. Jim

If you do deside to do the 7.5 I will help you the best I can. I have 28 spline after market axles and 28 spline mini spool and gears. That is about the best and only way to beef it up enough. OIf your gonna use a posi go with the Eaton... that will be the only chance in that department.

 

[Redline396]

if you are bent on using your 7.5 rear and want a strong posi unit,consider a
zexel-torsen unit.they are super strong and with a reasonable cost(300.00)
check it out. http://www.zexel-torsen.com.........good luck