8 3/4 goes boom

-
RockinRobin

RockinRobin

Well-Known Member
Joined
May 15, 2013
Messages
1,249
Reaction score
909
Location
Corsicana, Tx
My ring and pinion went out last night at the track. I was very careful to replace everything in the driveline of this car with stuff that could handle the horsepower, EXCEPT the ring and pinion gears! So Murphy's law has struck! The rear end has Moser yoke, spool and axles. Would like to replace with same gear ratio, but something stronger than stock.
Any suggestions as to a brand? Moser? Richmond gear? It needs to be able to handle about 800hp or more.
 
X 2 on posts 2 and 3. If you're hell bent on using the 8 3/4 check Yukon gear, lots of racers using them around here with good results. Just keep in mind no matter what you do 8 3/4 will never be bullet proof reliable.
 
skrews said:
X 2 on posts 2 and 3. If you're hell bent on using the 8 3/4 check Yukon gear, lots of racers using them around here with good results. Just keep in mind no matter what you do 8 3/4 will never be bullet proof reliable.
Click to expand...
Thanks! Biggest issue is cost of R&R ring and pinion vs whole new rear end/narrowing/new spline axles,brakes, welding, etc. I spent a lot of $$ on Race quality stuff for the 8 3/4 and it hung in there for almost 2 years with a used ring/pinion of unknown quality.
Will look into Yukon, how to you feel about Richmond Gear?
 
Dr Diff has Richmond but I don't know whether it's a race gear. I believe Scott (pettybludart) put a Strange Dana in his Dart with no issues since.
 
What does you car weigh? The lighter the better for an 8 3/4, it's not the gears that can't handle the HP, it's the case, it pushes the ring gear back as it tries to climb the pinion and the caps can't hold it. They do make a billet cap that is supposed to help but IMO you might as well go to a Dana 60 if you are going to spend $ on a rear that will hold up.
 
I was told that the failure of the ring and pinion gears is the result; not the cause. Reportedly the
bolts holding the carrier together are about a third the size of the ones in a Dana 60. They stretch
and then the spider gears start to climb over each other....then BANG!

This from a Chrysler powertrain engineer that broke a lot of them before switching to the Dana.
 
crackedback said:
Please pull the trans and check the sprag.
Click to expand...

This, if you are running an automatic, for sure.

If the motor ran away, then likely the overrun sprag will need to be replaced. Otherwise your next passes after replacing the rear end will involve putting a new trans in.

Brian
 
You got 2 seasons out of a used ring and pinion not bad..put a new set in and go..by the way NOTHING is "bulletproof" seen many a dana 60 go "boom" too...
 
gtsdude said:
What does you car weigh? The lighter the better for an 8 3/4, it's not the gears that can't handle the HP, it's the case, it pushes the ring gear back as it tries to climb the pinion and the caps can't hold it. They do make a billet cap that is supposed to help but IMO you might as well go to a Dana 60 if you are going to spend $ on a rear that will hold up.
Click to expand...
Car weighs 2850. Would like to try the cheaper fix for now and switch to DANA in the future.
 
wsuwrhr said:
This, if you are running an automatic, for sure.

If the motor ran away, then likely the overrun sprag will need to be replaced. Otherwise your next passes after replacing the rear end will involve putting a new trans in.

Brian
Click to expand...
the motor did not run away, but will pull the tranny anyway. it has A&A's best sprag in it, so hopefully it survived.....
 
ring and pinion will always be the weakest link in a 8 3/4.....
 
stroked340 said:
You got 2 seasons out of a used ring and pinion not bad..put a new set in and go..by the way NOTHING is "bulletproof" seen many a dana 60 go "boom" too...
Click to expand...

Yeah..... 800hp. Throw a set of gears in it and go.... NOT! Break that rear hard enough and you can break the trans case. That's the next weak link when that super sprag does its job... my cousins high 9 Duster proved that theory. Anything can break.... but for gods sake!! Push the odds in your favor.
 
Go Dana 60 and spend more time racing then wrenching.I added a billet yoke and a chromemoly shaft with 1350 U joints also.Its been 3 years and close to a 1000 hard passes without any issue.You,ll be dollars and time ahead.JMO
 
My 8 3/4 broke on the second pass my 408 hooked, one 1.38 60' then one boom. 3260# 69 Dart. The case flexes and the pinion gear tries to climb the ring gear. Richmond gears btw.

I fixed it, then ordered a new S-60 directly from strange, then sold the 8 3/4 to recoup some of the $$$.

I lucked out, my 727 wasn't hurt but I had to pull and take it apart to find out.

Spend the money on something stronger now and save your self some headaches down the road. My$.02.
 
I stock a thick, nodular iron 489 casting made with the same forged steel caps found on a 9" race case. This super duty 8.75" casting helps, but unfortunately, the 8.75" ring gear diameter and tooth contact area is not large enough for a heavy, torquey application.
 
Big tires, 2900lbs, 800hp. You need a Dana. I'd also check the housing to see if it is bent. The tubes bend on them too.
To finish the season maybe try a set of pro gears. Not any long-term solution but they might help for the short term. I would not expect to get a full season out of any 8 3/4 given the setup.
 
A friend is giving me a Dana.I gotta buy ends and cut to fit.9 inch ring gear is thicker though
 
The car in my avatar I raced 14 years 73 dart sport 3170 lbs 525hp 440 727 9" jw conv coil overs and latter bars 8.75 with 5.13-4.89 12.2-31.25 15 firestone or phoenix 1.42-1.44 60' 6.90 at 100mph I'd break a ring gear every 2-3 seasons and twisted the spines on drivers side axle 2 strange and 1 moser in 14 yrs yea in the long run should have gone dana. Sold that car 2010 bad idea!
 
I was very anti dana for quite some time. Now it's the only thing I'd run if I had to drop a nickel into a rear end.

Round about numbers for a complete with brakes Dana vs. an 8.75 that will handle big hp. 3200 vs. 5200$.

I needed to upgrade axles to go to SBP to LBP, you're already looking at 400$ or so. Then you'll need brakes. I'm a disk guy so lets say 500-1000. 750 average. now if it's for a show car you'll need to have it painted or coated. There's another 100 at least. That's assuming the stock parts will work and hondle your HP which in many cases, tey wont'.

So you're already over a 3rd of the way to an ideal width dana that will handle 1,000hp all day long and look great doing it.

Deduct what you can get for your 8.75 the new dana costs you about a 1,000 or so net cost.
 
You must log in or register to reply here.
-

Back
Top