8 3/4 & 4spd hi hp cars

[XMAN JR]

Who here is running a 8 3/4 & a 4spd with a 500 or 500 + HP motor ? If so, any problems or concerns ? How did you fix them ?

 

[1967coronet440]

Who here is running a 8 3/4 & a 4spd with a 500 or 500 + HP motor ? If so, any problems or concerns ? How did you fix them ?

Problems will come when you get traction, how heave of a car are we talking about here? Safest bet would be upgrade to a dana, 8 3/4 might last a while but for Me I would rather have piece of mind knowing I don't have to worry about leaving that rear sitting at the starting line or at the stop light.

 

[Jcharger]

That is what I have been told. I'm told it depends on how hard you are on it. I haven't broke mine yet, but also have not pushed it as far as it might.

 

[66Satellite47]

I bought my '65 Coronet 426 W with 1 good 4spd, 2 broken 4 spd's & a broken 8 3/4. A couple years later, put in the narrowed Dana. Never had a bit of rear axle trouble, many thousand runs with 550 -600 HP. Dana be good. Even though heavy.

 

[5.7 hemi]

As long as you run "street" tires you'll be fine with the 8 3/4. If you have really sticky tires, better up grade the rear end.

 

[66Satellite47]

Ya, if you spin the street tires, the 8 3/4 will be fine. If you have good hooking tires a fairly good big block will kill most 8 3/4's fairly quickly.

 

[Cranky]

Keep in mind whenever you blow a rear, you will most likely have damage elsewhere too. And a Dana usually runs about 50-60 lbs more than the 8 3/4.

 

[XMAN JR]

My son has a 69 barracuda original 383 4spd. He wants to run low 11s.

Problems will come when you get traction, how heave of a car are we talking about here? Safest bet would be upgrade to a dana, 8 3/4 might last a while but for Me I would rather have piece of mind knowing I don't have to worry about leaving that rear sitting at the starting line or at the stop light.

My son has a 69 barracuda original 383 4spd. He wants to run low 11s. He will be running street slicks. Sad thing is he already had his 8 3/4 rear narrowed & new moser axles, green bearing & long studs.

 

[Cranky]

How much does the Barrcuda weigh and at what rpm will he be launching it?

 

[mopar 3 B]

No mention of the back brace on the 8 3/4? Housing flex is what takes out most carriers.

 

[1967coronet440]

2 choices at this point then run it til ornate spills its guts or you can put it up for sale and use the money towards a dana, I paid about 3 grand for a strange s60 35 spline race axles, s track spool 4.10 gear chromoly pinion yoke delivered to my door.

 

[1967coronet440]

Shipping weight was 303 lbs

 

[Cranky]

No mention of the back brace on the 8 3/4? Housing flex is what takes out most carriers.

I've seen my share of broken 8 3/4's that were back braced too. It helps but it's not a cure all. When you are running a good deal of power AND a 4 speed, the hardened street gears will shave off the ring and I'm not sure you can find the softer pro gears for the 8 3/4 anymore. Don't wanna run the softer gears on the street anyways...

 

[mopar 3 B]

Honestly had more problem keeping the spider pin hole in the carrier in tact with the 4spd. I do understand the gear problem which seamed to be greater the lower the gear.
Never had that problem with 2:93 gears. But replaced clutches constantly.

 

[lewtot184]

i've broke 8 3/4's with a 383 4spd and no big power.

 

[mopar 3 B]

i've broke 8 3/4's with a 383 4spd and no big power.

Point taken. But some people seam to be able to brake anything while others can use the same thing for years with no problems.

 

[Cranky]

Point taken. But some people seam to be able to brake anything while others can use the same thing for years with no problems.

I started helping a buddy race his 69 roadrunner in 82. It was just a bracket car at the time but it was a 383 and 4speed and was running high 11's. Of course he was launching it at 6k rpm and well, when I drove it, I did the same. The car was 3200 at the time and the 8 3/4 was holding up for the most part but we did break one. Then along came a 440 that put it easily into the low 11's and that's when the carnage started. In went a Dana and all that stopped and we went on to running 10.70's with it. That's when the 833's said "can't do that for very long" lol. It got a Doug Nash pretty shortly. We tried lower launch rpm's to try and save parts but the car was faster doing the 6k thing.

 

[mopar 3 B]

I started helping a buddy race his 69 roadrunner in 82. It was just a bracket car at the time but it was a 383 and 4speed and was running high 11's. Of course he was launching it at 6k rpm and well, when I drove it, I did the same. The car was 3200 at the time and the 8 3/4 was holding up for the most part but we did break one. Then along came a 440 that put it easily into the low 11's and that's when the carnage started. In went a Dana and all that stopped and we went on to running 10.70's with it. That's when the 833's said "can't do that for very long" lol. It got a Doug Nash pretty shortly. We tried lower launch rpm's to try and save parts but the car was faster doing the 6k thing.

In 73 clutch replacement was the largest portion of the race budget. After distruction of the best single disk Hays had to offer going the the track became to large a financial burden. Some how life takes presidencies and bills need to be payed.

 

[Cornpatch MO]

If you do run a 8 3/4 be sure your trans. yoke , driveshaft, U joints , and differential yoke are for 7290 . And then that is "iffy" with sticky tires. Best use a billit steel differential yoke. Even with these parts, and Nitto Drag tires, I am " gun shy" about a 3-3500 RPM launch after having broken a 7260 diff yoke. With these Nitto's , I cant break the tires loose with an idle rolling start. 3:55 rear gears -sure loc, and about 400 horses. It runs good.
Thinking about getting tires with a little less traction, but I don't know what that would be....suggestions?.............................MO

 

[66Satellite47]

I agree with Cornpatch, an 8 3/4 will hold up for a while, just be prepared to change ring & pinion every so often. Be sure the yokes, U joints & driveshaft are stout. Forged or billet diff yoke and slip yoke, 3" thick wall chrome moly driveshaft, 1350 U joints are good. Exploding a driveshaft is no fun, been there. The tough parts cost, but sure save in the long run.