8.5 10 bolt in the mid-low ten's looking for ideas


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It's time to update the stock rear in my GN,and I'm looking for ideas,see what other people did,or think? It's just a street car with DR's,no trans brake I drive on the street alot,this car is fun,and I want to keep it that way! I already have a race car,and don't want this to be another! I have a 70 bb turbo & all the go fast stuff,now it's time to do the rear & drive shaft. I was thinking of 30 spline axles,and posi with ford ends,or do I just spend the bucks for a 12 bolt? A Dana 60 sounds overkill,and can't get lower than 354 gears with might be too much gear. What have other people done in the mid-low 10's zone? I'm also looking to put in a 6pt bar to keep the car together,I know the NHRA will want more but TOO BAD! like I said it's a street car! I'll make a few passes till I get kicked out & go home. I raced my other car deep in the 9's for a long time without a comp lic. Thanx for any input,and thoughts! Have a great new year Charlie
There have been many stock 8.5's that have gone deep into the 10's with just an after market sway bar, air bags and LCA. I believe there are even a couple in the 9's if my memory serves me correct but it's pushing it without upgrading the axles. If it's just a street car, I wouldn't even bother to be honest with you. I'm sure other will chime in......
For what you described, upgrading the 8.5 is the way to go. How big you go on the axles dpends on what center section you want t run and their availabilty in that spine count. You said you dont want a race car , so a Posi-locking type diff should be used. Most are only available in 30 spline last I checked.

Good Luck
cottons great pumkin has been 8.90 with an 8.5

i beleive Jack is running similar to what i run in my 86 which has been low 10s off T brake ,
33 spline mosers , moser clip elims , moser spool, good studs

as for the bar and NHRA tech , all you need is a 6 point for our cars and you dont even need the passengerside door bar so only 5 points are nescessary for tech to 10.0 and speed under 135 , and must be welded to the frame

and stock axles have no place on the track with a modified buick 6, read the NHRA rule book

once you hit 9.99 or faster than 135 it all changes
60 foots?
Launch Boost?
Launch RPM?

These are all better indicators than ET so far as how stout a rear end needs to be.

If and when I get the rear end in my T built I'll go right to Mark Jackson for their advice because they make the best stuff in the business, bar none, and I won't care if it costs a little more because it's incremental and cheap insurance.

I know that MW does not advocate candyazz 28 and 30 spline axles for anything serious. More like 35.


i suggest getting the TA girdle/cover along with big bearing axle change
weld axle tubes in also.
i have same setup with a spool in my big block car. i know the 8.5 can
hold up to a bit of punishment but like anything ,it has its limits.
if anything you will be ready for the next upgrade you do to engine.
Yes I know stock c-clips no good! can I buy a posi over 30 spline? will 30 spline hold up? I do have good adj control arms,& 1.5 bmr sway bar. Thanx
I have an Eaton 30 spline posi and Moser axles, with Ford ends.

Also went with TA perf rear-end gridle and brand new GM ring and pinion just to be safe.

I did a post at the time I was upgrading ( a couple years ago now) and there were quite a few guys running upper 10's with just Moser 28 spline replacement axles. I would go 30 splines just for the extra safety factor for low 10's.

Any of the big name suppliers will tell you you need at least 33 spline axles and a spool etc. That's what they told me at the time.

My car 60's in the 1.4's off the foot brake with no issues since the upgrade.
Thanx to all for their input! I also spoke to Cotton who set me straight! I'm goin 30 spline axles & eaton posi. It's a dam street car anyway! Don't think it will 60 ft faster than a high 1.40 anyway! Yeah everyone I called wanted to sell me 33 spline or better in a 9inch or Dana! While my race car has a 12 bolt with 33 spline with 17-33 tires that 60's in the mid 120's on the rear tires! The buick is just a street strip car,with is about 99% street! This things more fun than the race car anyway,can drive it anywhere,and play around on the street! What do most TSM guys do about a rear, and what do they 60 ? Everyone have a great new year. Charlie