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8 3/4 Sure grip options for a lot of abuse

Dodge Bros

Dodge Bros

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My brother (curiousyellow71) and I are working on installing of our old drag racing engine from our super street 10.90 index days in a car for the street. It is a 445 cid RB with stage 6 heads, solid roller cam, 1050 dom/max wedge combo, right around 700 hp in a 72 Charger. Big converter and a Transbrake, but I doubt we will use the brake until we get a Dana in it. We plan to do a Dana, just do not have time at the moment to get it all together, but we have a 8 3/4 that will drop in the car temporarily until we get time to take it to the track.

Last I counted we have 10 or more cars with 8 3/4s, I know they can break. But that also means once the Dana is ready we do not have a issue finding a home for whatever we decide to do in a 8 3/4. The last time we had slicks and a stock factory suregrip it quickly ate the spiders gears. What is out there that is better for abuse?

I just did a jegs unit and 3.55 in our 65 383 dart. Seems to be fairly strong looking and reasonable priced. Maybe appears to be a USA gear? Jegs didn’t list the mfg. It is clutch type. We are working on getting that car on the road, I think one is enough for now. LOL. Anyone broke one of those?

How about one of the Auburn Pro’s?

Reading the description the powertax set ups look interesting. They appear to get rid of the spider gears, which for us has been the weak spot on the carriers. I can care less about the clicking noise on a turn on this car. They also have one that fits inside the open carrier and one that has it’s own carrier. Any advantage to the fancier one? Sure appears it is as close as you can get to a spool.

Thanks for input!
 
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LOL...Our 71 Chevelle has a 8 3/4. HA! Have to call that one a posi or I can’t talk to the Chevy crowd. Sorry...got the title fixed...Carry on...:lol:
 
Curiousyellow71 said:
:popcorn:

yes where is the meme.
Click to expand...
This one?

Posi SG.jpg
 
IMO use a 489 or a 742 case, back brace it,top quality parts , good bearings, good axles and race .
 
The PowerTrax replaces the spider gears. This one was installed in an “open” differential. No problems driving on the street, track other than the audible clicking while turning. While cruising the hotel scenes parking lots during a car show at Carlisle Pa, it’s amazingly amazing how many people would comment that something’s wrong with the rear end as the PoweTrax loads and unloads. Lol Not only does it click but the car actually shakes her hiney as this happens. I like my spool better!!
upload_2021-1-30_6-42-24.jpeg
 
I'm using a real detroit locker in a 742 with 3.91s. No complaints. I have not tried the locker kits for open diffs, but i am contemplating trying a set in one of my nine inchers.
When i was putting the 8 3/4 together, a friend who ran a rearend shop could get the locker for me, for about the same price as a clutch unit. That is not true any more.
 
get yourself a Detroit Locker -- the mechanical lockup unit -- part number is Eaton Detroit Locker # 187SL14A ----can still be used on the street and track -- they hold up extremely well under Nascar use --- DO NOT confuse this with the True Trac gear unit --- the Detroit locker is a much better unit for abuse.
 
Thanks for the replies! :thumbsup: Wow, shaking the backend of the car sound like more than a clicking sound! That would stink to spend $400+ on a carrier and wish we did a spool!

Considered doing a spool and axles instead, but makes moving the carrier down to one of the other less powerful street cars pretty unattractive. Still would consider it though, this combo isn’t exactly something I want to drive a lot, the cam is 273/282 @.050, which on the street is going to be :mob:kind of snarly. Just doing a spool and some axles probably is a possiblity. Just afraid we might have more of a tendency to push that to the limit and spread it all over the track. Friend suggested we carry a bag of floor dry in the trunk so when the carrier explodes we are prepared. :)

The prices of the Detroit lockers initially scared me away. That is why I didn’t have that one in the initial post. When I did the search they looked like the were $650 to $750. Detroit list 3 different 8 3/4 carriers. 2 looked like helical set ups, and are available for bigger axles. Going by that, I assume the helical are strong yet? The helical appears to be more than we want to spend though. I did find a 14A on sale from one of the vendors for $567. I believe I spent $368 on the Jegs unit. If it is tougher though I would gladly spend the extra $199 if it will survive.
 
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Dr. Diff says they aren't selling the truetrac from quality issues...wonder what is going on.:poke:
Screenshot_20210130-062602_Chrome.jpg
 
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go with the locker i mentioned in my previous post --- they have been around forever and are proven effective -- even found their way into production cars ( Drag Pack Fords ) and used exclusively in Nascar racing -- if it will stand up to that use-- 800 hp ,, drop the jack at 6000 rpm ,, on concrete pit surfaces with slicks over and over again ,,, well???? the helical units are OK but the locker will last longer and take more abuse .
 
Drag race application..... don’t fool around. Go straight to a spool and don’t look back.
 
If you want the most stength for the least money, i would go 35 spline spool. You can probably get the spool AND the axles for less than a detroit locker. But that isnt real friendly for eventual street use.
If you want the most bulletproof limited slip, i would go with the detroit locker.I believe it is substantially stronger than the clutch type. If you want the most strength, worth the $200 price increase.
But, since you want this to last a while, till the dana replaces it, and you want it in a street car eventually, i would get the clutch suregrip from Dr Diff, and try not to break it till the dana arives.
 
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33 IMP said:
If you want the most stength for the least money, i would go 35 spline spool. You can probably get the spool AND the axles for less than a detroit locker. But that isnt real friendly for eventual street use.
If you want the most bulletproof limited slip, i would go with the detroit locker.
But, since you want this to last a while, till the dana replaces it, and you want it in a street car eventually, i would get the clutch suregrip from Dr Diff, and try not to break it till the dana arives.
Click to expand...
Yes... you nailed the delema. Trying to walk the line between racing and street and then throwing the cost into the equation.:eek:
I don't mind spending some money, but it really stinks when you brake something after emptying the bank....I guess that's racing.Lol

Maybe if we left the line with a 2 step on the brake the 8 3/4 would survive? Our 60' times were around 1.43 with this engine/ transmission before and that was a soft launch with a 2000rpm 2 step. The car is heavier this time with 75 more hp and drag radial vs the 14x32 slicks ran. I know guys go fast with 8 3/4s....until they go bang.
Dana 60 oem sure grip any heavier? I think we have one with a 31 spline? We would have to narrow it and buy axles.
THANK YOU Guys for the input!
 
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I'm pretty sure with that much power and hard launches it's not a matter of if but when you will break it or the axles.

My buddy has a 55 Chevy with a 454 and a 31 spline 9" Ford that I built. Everything is holding up fine except he is bending or twisting axles. 100 passes and the rear brakes start squeaking. The Moser axles were like a banana. He has Mark Williams now and they are much thicker cross section but starting to bend. He needs to go 35 or 40 spline. The car is running mid to high 11s with a 4 speed.
 
I always remember Monte Smith saying that drag radials are harder on drivetrains than slicks. He said that slicks can still work good with some wheel spin, and sometimes wheel speed is actually preferred with high horspower cars. Drag radials need to be dead-hooked. If they spin, the car needs to be pedaled to hook them back up.
Your quandary of putting money into a 8 3/4 and hoping it lives.... is exactly why people invest in dana's! You now have more power, more weight, and a transbrake. I would put the bare minimum into an 8 3/4, if anything.
The sooner the dana, the better.
 
I appreciate the input.

We talked our axle options over. Our conclusion was if we do a spool we need to go straight to the Dana. Which we may just go ahead and do. The spool for the Dana and 35 spline axle’s from Dr. Diff is cheaper than the 8 3/4 locker or sure-grip carriers.

But, that said, we have other car’s that are pushing the limits on the 8 3/4. So it still makes some sense to start with the 8 3/4 and move the pumpkin to another car when the Dana is ready. We are splitting up our S/ST parts between a couple cars. The other S/ST engine going in our 69 bee, it won’t be as powerful, but planning on running the 440 and the other tranny brake w/5000 stall and the 8 3/4 at the back. Probably do the spool and big axles, though. Spool and axles appear to be the most bang for the buck in an abused 8 3/4. Our 72 Satelite Sebring is getting a stock appearing 542 in a 400 block, not sure what it will end up with for a stall, but hoping to keep the 3.23s, it is next on the engine list. Seems like it is a OEM clutch type carrier in it’s 8 3/4. Mostly a cruiser, but that is going to be a lot of TQ to manage. The stage 6 and the bee engine are after it. Our 69 Charger still has a 8 3/4 with the 510 and a 4200 stall with 8 3/4 4.10s, cone diff, and 295/65-15 Mickey DR’s. Just a guess, but if radials are harder on stuff, these are probably the kiss of death to the carrier in that car. Might need to stay with biased type tires. We have some M&H street masters that have the wrinkle type sidewalls. Maybe that type tire is a better choice on our 8 3/4 cars?

So far, it appears the best bet for better carriers are these two:

CB753433-ACF4-45A4-B742-88060DD867A8.jpeg BB31DC1C-0BCA-464D-B016-C49B6F110D70.jpeg 824D04E1-B93E-4983-9310-BA1D65E33864.jpeg 6C55EEBC-872F-4E28-A631-C73BCE9AE23A.jpeg
 
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Googled 35 spline axles and spool. Ebay shows a lightweight steel 35sp spool, for $125 plus shipping, and a pair of 35 sp axles for $300 with 3" studs and bearings. Both from Dr Diff. Strongest for least money, saving a few bucks for the dana.
 
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