Rebuild Diff. or spool for drag car?

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RockinRobin

RockinRobin

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Car already has narrowed rear, 8 3/4 Sure grip. I'm trying to decide whether to take the diff. to a shop and have them go through it or just replace it with a spool. Spool looks to be cheaper, lighter, more dependable. Any reason I wouldn't want a spool?
Also the yolk has straps to attach the U joint, should I change to U bolts?
Will be about a 10 second car.
 
No good reason not to have a spool in your application. You got all the benefits down.

As for the yoke, I have gone to billet steel yokes on my 8 3/4 rears and have had no problems and peace-of-mind for many years. I found that over time and hard use, it is possible for the regular style yokes to spread, leading to the u-joints loosening & pounding out if not caught in time. Spicer solid u-joints are also used in the race car.
 
Locomotion said:
No good reason not to have a spool in your application. You got all the benefits down.

As for the yoke, I have gone to billet steel yokes on my 8 3/4 rears and have had no problems and peace-of-mind for many years. I found that over time and hard use, it is possible for the regular style yokes to spread, leading to the u-joints loosening & pounding out if not caught in time. Spicer solid u-joints are also used in the race car.
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X2. Sell the current differential to someone building a street car to offset the price of the spool or keep if for another project.
 
Would I need any special tools to install the spool myself?
Myron, you had mentioned Spicer as your choice for U joint, do you have a brand preference for billet steel yoke?
 
RockinRobin said:
Would I need any special tools to install the spool myself?
Myron, you had mentioned Spicer as your choice for U joint, do you have a brand preference for billet steel yoke?
Click to expand...

I believe one manufacturer is "Victory". The few that I've seen from different dealers appear to be the same, including Mancini, Mopar, differential vendors and some trans builders. I believe Mancini is one of the few that have a 7260 steel billet yoke for a 10 spline 8 3/4" pinion.

Anytime you replace parts of a differential, you basically have to recheck the gears, like when setting up new gears. You'd need a press as well for the bearings. I don't think a Sure-Grip and spool take the same carrier bearings.
 
Locomotion said:
I believe one manufacturer is "Victory". The few that I've seen from different dealers appear to be the same, including Mancini, Mopar, differential vendors and some trans builders. I believe Mancini is one of the few that have a 7260 steel billet yoke for a 10 spline 8 3/4" pinion.

Anytime you replace parts of a differential, you basically have to recheck the gears, like when setting up new gears. You'd need a press as well for the bearings. I don't think a Sure-Grip and spool take the same carrier bearings.
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Thanks, will check with Mancini for the yoke.
 
Well, it looks like I will be replacing axles, diff, yoke and all bearings. All of my stuff is 30 spline, Moser says its rated up to 600 HP, so will be upgrading to the 35 spline stuff to be safe, rated at 1000 HP. Gonna stick with the ring and pinion and case I have now, might be able to upgrade them later....
 
RockinRobin said:
Well, it looks like I will be replacing axles, diff, yoke and all bearings. All of my stuff is 30 spline, Moser says its rated up to 600 HP, so will be upgrading to the 35 spline stuff to be safe, rated at 1000 HP. Gonna stick with the ring and pinion and case I have now, might be able to upgrade them later....
Click to expand...

"Ratings" have too many "it depends" associated with them. Weight, HP, torque, traction, gearing, etc. OEM axles can work for a while behind a high HP car. But aftermarket 30, 35 and 40 will all last longer respectively.

I knew of an IHRA Stock class 360 crate motor Duster using the OEM 4" bolt pattern axles for at least a year or two. Mid-high 10's with low-mid 1.40 60' times weighing probably 3,200 - 3,300 lbs. Eventually, an axle broke or was found with a "twist" starting. I broke a 35 spline axle in a Dana 60 (same as 35 spline 8 3/4) with a 360 W-2 motor running mid 10's and around 1.40 60' times at around 2,850 lbs. But this was after 10 years and a LOT of racing. My current car had a 35 spline 8 3/4. 1.47-1.50 60' times running low-mid 11's at 3,550+ lbs. Been at it for many years with no issues.

But 35 spline is a smart choice. I really like the aluminum cases, but they are expensive. They do make new, aftermarket nodular iron cases which are said to be better than OEM and cost a lot less than the aluminum ones. Good set-up is important and I have been getting my gears cryo'ed and REM finished as well. It seems to have helped longevity.
Gear teeth tend to be the weak link in 8 3/4 rears.

http://www.evansperformance.com/home2.html
 
Tried the aftermarket cast cases, not getting the longevity with them either.

30 spl is rated to 6200 ft lbs, not 600hp. 35spl is rated 9600 ft lbs.

However you can break a 40 spl axle with 1000 ft lbs and simple wheel hop
 
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