I have original 3.23 type o posi 28 or 27? spline axles.
Running a healthy 455, tremec 5spd with2.89 first and
275/50-15 bfg drag radials.
Worried that I may be close to breaking parts, and I was thinking of
going to a 3.90 or at least 3.42.
Any opinions and/or experience with this rearend at the track is appreciated.
Thanks to all.

 

Well no problem with the rear talking some track time. The bigger problem is PARTS- You can not get the 3.42 3.90 gears for this rear at the moment.

Posi units we have bigger axle shafts we can supply even a FULL spool we can get you.

JUST NO STINK IN gears as MOTIVE Gear is F- ing up the whole thing with the Richmond gear buy out... It has been a year already and STILL NOTHING.

Jim
J D

 

Hopefully they sort that out. For now I cringe when shifting 2nd wot.
Currently 12.5@110 1.88 60ft. 3800 lbs with driver.
How fast have these rears gone with a std car.
I could launch the car a lot harder/higher but of course that means
more stress.

 

I stick shift car will put more blunt force to the rear,compared to an automatic,unless the auto has a trans-brake. The O-axles have softer axle shafts,compared the the 71-up shafts. Those are usually the first thing to break in those rears. An automatic car can dip into the 11's at 3800lbs,when flirting with axle breakage.Not as fast with a stick.

 

Thanks Monzaz and 507olds.
If available I intend the 3.90 ring and pinion to go in. This could take the car into the mid/high elevens, no?
Being a #'s 4 speed car I have no intention of a cage or other required safety items to pass ihra specs at 11.5.
Most of us want to go faster next year than this year, that's all the fun.
Is there any options for this housing with better axles, safe to this level (11.5).
Axles, 8.8 carrier machined?
This is a street car frequently driven, 20 odd runs a year aat the track.

 

If you are considering aftermarket axles,then I would upgrade from the 28-spline to the 31-spline,and get a carrier to match. The cost of the axles is the same,and the aftermarket posi units are designed for the 3:08/3:23 GM gears,or the Richmond gears that were made.I had a few Eaton carriers remachined for this purpose.I assembled them with the good knurled steel clutches,not the polycarbonate clutches that all the new units come with.The reman'd Ford units are good for street use,but there is only one clutch available for those,and that is the only thing I don't like about those units.The helical gear Tru-Tracs are real nice for street use,but not intended for drag race use.

 

507olds,
thanks, do you know carrier #,s and axle #s?
Are we talking about upgrading my carrier and axles to the 3.42-3.90 factory carrier. These were 31 weren't they? Should fit my housing?
axle code 'sf' is what I believe I have.

 

The carrier that you have now is the # 671. It is 28-spline,an is made for the 3:08/3:23 GM gears. It is also correct for the Richmond gears that were made.
The axles will be custom-made,new axles,from Moser,Strange,etc. The cost of a 28-spline axle is the same as a 31-spline axle,so you you are willing to change the carrier,now would be the time to do both.
The new carriers are also made for the 3:08/3:23 GM gears and the Richmonds,so you can do a carrier and axle upgrade,while retaining your existing 3:23's.

 

So a new 31 spline carrier is available from Eaton? Same ring mount backspacing as my 3.23 carrier and the 3.42/3.90 gears that were made for this carrier?
So, factory 3.42,3.90 gears would not work with this carrier, and I am told new Richmond gears are not currently available.

 

I took the Eatons for the 8.8 and the 8.5 GM,and had them remachined.
The factory 31-spline O-axle carrier is #672. These are still floating around,but the original GM 3:42's or 3:91's are becoming scarce. Either way you cut it,the availability of the gears is the issue.

 

Will the factory 672 carrier and 31 spline oe axles be ok to low elevens?
As the aftermarket setup is a last resort for this car.

 

No. The carrier can,but the OE shafts,even the thicker 31-spline,were still made of the softer material they used back then. I had a pair from a stock W31 stick. At that looked more like threads than splines. They were twisted pretty good.

 

Thanks,
Will aftermarket axles in a 672 carrier hold up?
Provided of course I could find one.
I assume an eaton 8.8 machined would use slightly different31 spline axles. Of course the gear availability would still be an issue right.

 

Yes,I have plenty of them out there doing it,and own some of my own. The 31-spline Eaton will work as well. It is just a matter of finding gears.

 

Great, I will look for a oe 672 w/gears and if I find one by end of February I will purchase aftermarket axles. If I have to use previously enjoyed gears I will get the pinion depth and carrier shimming as close as possible to existing pattern and hope for the best.
Otherwise I guess its the eaton option.
Hopefully someone posts the Richmond gear availability if it happens.

Much appreciate the advice.

 

I have one true trac 31 spline I made for a special occasion...This might be the one...lol. JUST NEED THE DARN GEAR SETS

Oh and I think I have that 672 carrier you might want too. I just worry that if you use the 672 and blow the parts you will have trouble finding clutches and side/ spider gears for this unit.

PM if you have some interest...wish we had the gears for you Just do not. I will keep my eyes open in this area of the country for you. Jim Mitschke
JD

 

Bruce Ponti got the shims and clutches made.
the side and spider gears, gotta find em used. or NOS I suppose

 

I would still like to get the 672,but you never said what you wanted for it,bare or assembled.

 

I suppose I'll have to find a gearset before either carrier will help.
Gotta be out there somewhere, needs to be complete by april.

Thanks to all.