7.5" Rear, 200-R4 Stock, with a 305 in front

pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
24,750
10,212
113
Kitchener, Ontario
#11
Your not going to blow up the 7.5 any time soon so why rush. Why not keep looking and wait for a 8.5 to pop up. Or do the upgrades and for sure an 8.5 will appear making you ask yourself, w the f did I do...
 
64nailhead

64nailhead

G-Body Guru
Dec 1, 2014
916
1,043
93
Upstate NY
#12
If you want to upgrade the 7.5 on the cheap, then you need this : http://rover.ebay.com/rover/1/711-5...0001&campid=5335822911&icep_item=183510173004

with a set of junkyard 2wd S10 axles from a 7.626 (28 splines.) Then take a piece of 3/16" or 1/4" plate steel and make a spacer to put between the axle flange and brake backing plate.

I ran this setup for a full summer with 400+whp in front of it - no problems and never broke. Rear is in the basement as a spare for the 8.5" we found. Auburn's are over rated IMO.

BTW, we run a 200-4R as well, the only difference between then and now is that the new motor makes 650+ to the wheels before we flip the boost control switch :):)
 
Myles

Myles

Apprentice
Jun 17, 2011
55
13
8
#13
I had a stock 305 going 15.5, broke the 7.5 spiders because it didn't hook and the street tires hopped.

Now with slicks over 1200 passes on the 7.5, stock axles with 4.11 and a jegs mini spool. 383 4 door '83 [email protected] 325hp 390tq.

With those little 7.5s I think it's going to come down to how well its assembled.. just dont let the 7.5 hop no matter what the power. (Just my experience)
 
Myles

Myles

Apprentice
Jun 17, 2011
55
13
8
#14
I had a stock 305 going 15.5, broke the 7.5 spiders because it didn't hook and the street tires hopped.

Now with slicks over 1200 passes on the 7.5, stock axles with 4.11 and a jegs mini spool. 383 4 door '83 [email protected] 325hp 390tq.

With those little 7.5s I think it's going to come down to how well its assembled.. just dont let the 7.5 hop no matter what the power. Just my experience.
 
B

bracketchev1221

Master Mechanic
Jan 18, 2018
401
362
43
#15
I went 13.60’s as well with a stock Monte ss 3.73 rear.
 
DRIVEN

DRIVEN

Geezer
Apr 25, 2009
5,735
5,485
113
Owyhee County
#16
Gonzo, your combination will be fine. Similar to mine, in fact. My 305 is factory stock with the exception of an L82 intake, which I suspect is just an aluminum version of the stock cast iron intake.
I put my 7.5 together with junkyard parts using a 3.42 gearset from an S10 and a 26 spline posi carrier from an 87(?) Camaro so that I could reuse my original axles.
My 200-4R is essentially stock with a rebuilt 2200 converter. It was pulled from a well maintained '90 Caprice wagon.
I used a gear calculator to determine that my 3.42 were the overdrive equivalent to my stock 2.29s with my TH200 so my cruise RPM and mileage stayed exactly the same.

I mostly drive my car like an old man but occasionally beat on it and it's been to the dragstrip a couple times. Held up fine with this combo for several years but I've got changes in the works that will require a beefier rearend and some transmission upgrades.
 
Gonzo1970

Gonzo1970

Master Mechanic
Supporting Member
Sep 30, 2018
418
451
63
#17
Gonzo, your combination will be fine. Similar to mine, in fact. My 305 is factory stock with the exception of an L82 intake, which I suspect is just an aluminum version of the stock cast iron intake.
I put my 7.5 together with junkyard parts using a 3.42 gearset from an S10 and a 26 spline posi carrier from an 87(?) Camaro so that I could reuse my original axles.
My 200-4R is essentially stock with a rebuilt 2200 converter. It was pulled from a well maintained '90 Caprice wagon.
I used a gear calculator to determine that my 3.42 were the overdrive equivalent to my stock 2.29s with my TH200 so my cruise RPM and mileage stayed exactly the same.

I mostly drive my car like an old man but occasionally beat on it and it's been to the dragstrip a couple times. Held up fine with this combo for several years but I've got changes in the works that will require a beefier rearend and some transmission upgrades.

Perfect..

Getting the headers/exhaust put on after the holidays.. I may or may not put the intake on (need to clean it up a little) before it gets warmed up again. I would have to rent a stall at the auto-hobby shop to do it, but run the risk of needing a part and being stranded.

Got my eye on the same carrier (not the gov-lock, the auburn style) from a S-10 for the 26 spline.. 3.55's If I get them for the right price, I may jump on them befoer the exhaust.. at least I will have the parts on hand, ready to go.

Thanks everyone!

-Gonz
 

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