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8 3/4 Horspower limits

Cojohnso1 said:
That's actually a fair question. You know. I don't know? I assumed so? Like Strange Engineering? I have been researching some gearsets for Dana? But my A-body is the only 8 3/4" I have. And holding strong. (At least for the moment.)
Click to expand...
I assume you know about racing (pro gears) vs street gears. Even back in the early 80's, they were limited in gear selection then they became hen's teeth so we used whatever we could find and lots of them came from wrecking yards but then when we needed stuff like 4.56's and 4.88's and wrecking yards didn't have that sort of ratios usually. After shaving teeth for the 3rd time, we stuck a Dana in the car and never looked back. 'Mo power' was added at the same time and the car was going high 10's and still was running a 4 speed. Even that didn't last all that long launching at 6k. Fun times though lol
 
No pro gears available for 8-3/4 as far as I have found.
 
Cranky said:
I assume you know about racing (pro gears) vs street gears. Even back in the early 80's, they were limited in gear selection then they became hen's teeth so we used whatever we could find and lots of them came from wrecking yards but then when we needed stuff like 4.56's and 4.88's and wrecking yards didn't have that sort of ratios usually. After shaving teeth for the 3rd time, we stuck a Dana in the car and never looked back. 'Mo power' was added at the same time and the car was going high 10's and still was running a 4 speed. Even that didn't last all that long launching at 6k. Fun times though lol
Click to expand...
I have actually heard that street gears may be more favorable. For street/strip? Pro gears reported too hard a material. So unless for big time power? Aftermarket street gears are plenty tough for most applications.
 
If I'm not mistaken, pro gears are softer, better to absorb the shock.
 
Did just a little research. Found pro gears for a 7 1/2 Chevy (why?!) but nothing for 8 3/4. Some Dana gears, lots for a 9" and even some for a ten inch (?) Ford.
 
33 IMP said:
Did just a little research. Found pro gears for a 7 1/2 Chevy (why?!) but nothing for 8 3/4. Some Dana gears, lots for a 9" and even some for a ten inch (?) Ford.
Click to expand...
Good question!! Funny how an 8 3/4 is only a 1/4" smaller than a 9" and is pretty dang strong but the 9 got the nod for being the rear end of choice......even though in stock form, the 9 might be just a tiny bit stronger than the 8 3/4. Thing is, the 9 takes more hp to run than just about any other rear end out there!
 
Cranky said:
Good question!! Funny how an 8 3/4 is only a 1/4" smaller than a 9" and is pretty dang strong but the 9 got the nod for being the rear end of choice......even though in stock form, the 9 might be just a tiny bit stronger than the 8 3/4. Thing is, the 9 takes more hp to run than just about any other rear end out there!
Click to expand...
To be honest, I think it's cause the Mopar guys that NEED a pro gear had already converted to a Dana first. And I agree , the ordinary 9" is not some killer strong piece. The grey iron centers with 28 axles aren't any stronger than an 8 3/4. The nines rep comes from all the good aftermarket parts available for it.
The hypoid angle of a nine, and the third pinion bearing is what makes the gears stronger than the 8 3/4. Also the reason why they are inefficient
 
33 IMP said:
To be honest, I think it's cause the Mopar guys that NEED a pro gear had already converted to a Dana first. And I agree , the ordinary 9" is not some killer strong piece. The grey iron centers with 28 axles aren't any stronger than an 8 3/4. The nines rep comes from all the good aftermarket parts available for it.
The hypoid angle of a nine, and the third pinion bearing is what makes the gears stronger than the 8 3/4. Also the reason why they are inefficient
Click to expand...
If you look at how close the front and 'rear' pinion bearings are (not including that 3rd 'nose' bearing), the 9 needs that 3rd bearing! And if you look at the stock setup, I don't see how that 3rd bearing fit does much. From the ones I've seen (stockers), the casting looks pretty weak. But what made the 9 so popular before they got really popular with the aftermarket was the choice of gear ratios and that alone made the CRAPCAR guys look at them pretty hard and then so did the aftermarket. The aftermarket saw $$$$$$$. The short track guys could make a 5% gear change in many instances and improve their lap times without over revving and well, that option wasn't available with the 8 3/4's.
 
Doesn't apply to most of us but part of these axles popularity is just because they are NOT GM 10 BOLTS LOL.
I remember a particularly rough night at the dragstrip when the announcer was begging the Chevy heads to give any other corporate axle (Ford9, Mopar or a Dana) a shot.
 
Lefty71 said:
Doesn't apply to most of us but part of these axles popularity is just because they are NOT GM 10 BOLTS LOL.
I remember a particularly rough night at the dragstrip when the announcer was begging the Chevy heads to give any other corporate axle (Ford9, Mopar or a Dana) a shot.
Click to expand...
I don't know about being a "Chevy head" (I suppose I was at the time) , but I did have a V8 vega...... with a narrowed 8 3/4 under it.
 
Cranky said:
Was the spool a 35 spline unit and where did the axle break? I know they make a 30 spline spool for the 8 3/4 but never saw one for a 60. And sorry about your injuries....
Click to expand...

35 Spline/solid not rifle drilled/Broke on the flange end of axle. I am lucky the wheel/
tire/drum missed the starting line crew tossed it 300 ft. like a bazooka shell!!
 
padam said:
Of course you quit racing after that.
Click to expand...

My boy finished 3rd @ NHRA World Finals in November and I finish 5th in Stock.
We were Mopar Top finisher. We have been Mopar Top Finisher more than any other
team.
We are aware of the risks and are fortunately lucky enough to Pray with RFC Pastors
every pass at was Nationals/Divisionals.
I know some people only watch TV or in Stands to see the accidents = And I understand that. However, keep in the back of your mind that the wreck can be
life changing for the driver = sometimes life ending. I was standing on the rail watching at Arizona Nationals when a tire came of Anton Browns race car at finish.
We scattered fast enough BUT an lady in a wheelchair next to me was cut totally
into 2 Pieces and died instantly.
 
Cranky said:
Are pro gears being offered for the 8 3/4 these days? That was most of the problems in the past when they quit producing them....
Click to expand...

No Pro Gears for the last 10 years.
They were actually softer but absorbed impact load better.
However, I put a set of 4:86 Pro Gears that we found sitting in
a speed shop for many year = The 4000Lb. High 11 Sec. 318
Wagon Knocked several teeth off on the first pass in first 10 Ft.
off the line. The driveshaft would spin and the wagon just sat still
with the engine running in gear. I killed the overriding clutch in the 904
trans as well
 
GTX JOHN said:
No Pro Gears for the last 10 years.
They were actually softer but absorbed impact load better.
However, I put a set of 4:86 Pro Gears that we found sitting in
a speed shop for many year = The 4000Lb. High 11 Sec. 318
Wagon Knocked several teeth off on the first pass in first 10 Ft.
off the line. The driveshaft would spin and the wagon just sat still
with the engine running in gear. I killed the overriding clutch in the 904
trans as well
Click to expand...
You busted a pro gear with a 318 on the first pass.? Pretty good endorsement for a Dana, for people that want to know if their 8 3/4 will last.
 
33 IMP said:
You busted a pro gear with a 318 on the first pass.? Pretty good endorsement for a Dana, for people that want to know if their 8 3/4 will last.
Click to expand...
Pro Gears were too soft for that heavy a car (For about 10 years only available 488 ratio in pro gear)
Regular Gear sets lasted almost forever if set up right in old days.
Chinese/Italian junk = who knows
I have a stash of a dozen sets of early gears.
I only run 742 case = Can not find many options for 741.
I do not use 489s much even with crush sleeve eliminated.
I make hundreds of runs each and every year on 8 3/4's
Eliminating the run out on the carriers/spools in critical but
it is on Dana 60's as well for longevity.
I have 8 race cars with 8 3/4's
I have 3 Transbrake Fast cars with Dana 60's
 
Last edited:
GTX JOHN said:
Pro Gears were too soft for that heavy a car (For about 10 years only available 488 ratio in pro gear)
Regular Gear sets lasted almost forever if set up right in old days.
Chinese/Italian junk = who knows
I have a stash of a dozen sets of early gears.
I only run 742 case = Can not find many options for 741.
I do not use 489s much even with crush sleeve eliminated.
I make hundreds of runs each and every year on 8 3/4's
Eliminating the run out on the carriers/spools in critical but
it is on Dana 60's as well for longevity.
I have 8 race cars with 8 3/4's
I have 3 Transbrake Fast cars with Dana 60's
Click to expand...
What do you do to eliminate runout? Re-cut the carrier or shim the gear?

Oh and I didn't really figure you quit racing after that wreck.
 
Recut the carrier as runout is very critical
Easy on a spool to set up.
That allows me to set the backlash closer.
You can also Microfinish the gears if you have a thick Wallet.
 
GTX JOHN said:
My boy finished 3rd @ NHRA World Finals in November and I finish 5th in Stock.
We were Mopar Top finisher. We have been Mopar Top Finisher more than any other
team.
We are aware of the risks and are fortunately lucky enough to Pray with RFC Pastors
every pass at was Nationals/Divisionals.
I know some people only watch TV or in Stands to see the accidents = And I understand that. However, keep in the back of your mind that the wreck can be
life changing for the driver = sometimes life ending. I was standing on the rail watching at Arizona Nationals when a tire came of Anton Browns race car at finish.
We scattered fast enough BUT an lady in a wheelchair next to me was cut totally
into 2 Pieces and died instantly.
Click to expand...
Oh man, I'm not one that watches to see crashes and heard about Brown's crash. Was at a National Event at the Houston track a lot of years ago (back when they were still using those goofy looking small front wheels in TFD) watching qualifying and a TF dragster crashed hitting both walls crossing over in front of Darrell Gwynn (1989?) but missing him. IIRC, it was Connie Kalitta that hit the wall. The sound of the impacts was crazy loud. Darrell Gwynn looked visibly shaken when he finally pulled back into the pits. Years later a buddy of mine with his low 9 second car tried to knock down the wall (his second time) when he got out of the groove and tried to drive it though. He was ok except for a mind concussion. I don't hang around people that go watch just waiting for a crash to happen. Somethings wrong with that mentality....
 
Cranky said:
Oh man, I'm not one that watches to see crashes and heard about Brown's crash. Was at a National Event at the Houston track a lot of years ago (back when they were still using those goofy looking small front wheels in TFD) watching qualifying and a TF dragster crashed hitting both walls crossing over in front of Darrell Gwynn (1989?) but missing him. IIRC, it was Connie Kalitta that hit the wall. The sound of the impacts was crazy loud. Darrell Gwynn looked visibly shaken when he finally pulled back into the pits. Years later a buddy of mine with his low 9 second car tried to knock down the wall (his second time) when he got out of the groove and tried to drive it though. He was ok except for a mind concussion. I don't hang around people that go watch just waiting for a crash to happen. Somethings wrong with that mentality....
Click to expand...
Sometimes I think that the current no-prep craze is promoted for the i-wanna-see-a-crash crowd.
 
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