8 3/4 Info needed

[528Wedge]

Hello, Gents building a 62 Dart and have new unfired 505 inch with Victor heads and intake and large comp solid . I was wondering with all aftermarket performance goodies added to 8 3/4 what is safe max HP it could handle ??
I will be running 727 [ front & rear ] 4 gear planetary's with a transbrake . What are some members cars running with heavily modified 8 3/4 units - thanks Chris

Detroit locker / Backbrace / etc all top quality items .

 

[ironside]

It's a multitude of factors that kills the 8.75. HP, weight, torque and the transbrake really. If your only going to make a few passes a year you'll probably get by. But that's a pretty heavy car with a brake and a good amount of torque. It's more of a WHEN will it break not IF.

I have a buddy with a foot braked 3300 dart that runs high 9's without much problems but only a few times a year. But the cars been together a while too.

In my opinion I'd go with a dana or 9". You'll be money ahead. Usually when an 8.75 breaks you'll have to pull trans as well, plus whatever parts it hurts in the pig. You can break a dana or a 9" too, but it just happens much less frequently.
Good luck.

 

[1969CoronetR/T]

I put a Moser 489 case with a Detroit Truetrac in my R/T. I hope the 8-3/4 will hold up.

 

[66Satellite47]

One thing to consider with the 8 3/4 is gear ratio, actually the number of ring gear teeth. I'd say get the combination in your approximate range that has the fewest ring gear teeth compared to pinion teeth (largest physical size ring gear tooth). My experience is limited though, I switched to a Dana after the 3rd 8 3/4 ring & pinion. Never broke a Dana with 3550# car, 500 - 600 HP 451 & many, many hundred runs.

 

[Budnicks]

By the time you spend enough to make the 8.750" last
you could get a Dana-60
or S-60 from Strange Engineering even better yet

I've had a few high $$$ 8.750" rear ends in drag cars,
mainly they were much lighter,
I was on a mission to have an 1800# car with driver
{not the best reason when the weight is over the rear tires}
even in an Altered that made well over 1500hp at the rear wheels,
they lived it ain't cheap either,
especially back then it was all custom parts from Lenco IIRC

but housing $1000+ like a Moser then it needs to be backbraced
alum. MP 742 center section another $1000+
35 spline aftermarket hardened or drilled axles or bigger/more splines $400+
to live under high hp hard launches
dead hook launches or trans-brake launches over 5000rpm's
spools are cheap $200, either way
Pro-gears $200 are softer & last a little long under high shock loads,
but wear very quickly too,
not really the best for any street use or very limited at minimum,
hard to find sometimes for a 8.750" in the gear ratios you actually want...
Eaton lockers $500+
or true-tracks or sure-tracks $400+
either won't be the best or strongest, but are relatively strong for a 8.750"
the brakes are the same basically between 8.750" & the Dana-60

 

[dvw]

Lets see. Sons 3800lb 62 Plymouth with a brake. Drag radials and a 3.23 8 3/4. Broke the sprag, then the pinion shaft and 90% of the ring gear teeth, then stripped the front planet. 3 pin planets, never hurt the planet gears, just stripped the hub. Installed an A&A super sprag, steel front planet and a junkyard Dana (used the 3.55 that came from the junk yard). Never an issue since.
Doug

 

[383man]

10.70's at just over 3700 lbs in my 63 with a basically stock 8-3/4 as the only mods are a Detroit Locker. I only make a few passes a year but its been holding up like this with the 10 second eng since 2011. I dont recomend running a stock 8-3/4 with a 10 second car but with only a few passes a year I have gotten away with it. Ron

 

[66Satellite47]

10.70's at just over 3700 lbs in my 63 with a basically stock 8-3/4 as the only mods are a Detroit Locker. I only make a few passes a year but its been holding up like this with the 10 second eng since 2011. I dont recomend running a stock 8-3/4 with a 10 second car but with only a few passes a year I have gotten away with it. Ron

Yup, that's the key, "only a few passes". I really only works if the car is light, the arm isn't real long & the tires aren't real sticky, then it'll work for a while. When I bought my '65 Coronet w/426 Street Wedge - 4 spd, 3700# 12.6 car it had one axle with 1/16 turn in the splines.

 

[528Wedge]

Thank-you Gents considering that I have a D-60 and a new spool I think I will build it instead of 8.7/5 . Next question is I have a friend whose father regularly attended military auctions and he has several GM Dana 60 gear sets from GM 3/4 ton 4X4 military trucks and was wondering if their is a difference in front end gear and rear gear thanks again for all the help Gents yall are the best .

 

[dvw]

Front gear sets are reverse rotation. Plenty of junkyard stuff out there. We did the axle for the pictured 62 above for $600 in parts. New ends,shafts, side bearings, and spool. The original pinion bearings and gear set were reused. Did the labor ourselves.
Doug

 

[528Wedge]

Thanks Gents , I believe the D60 will be used and when I get my car back from blasting I will put the 741 case up on forum cheap i have 2 of them .

 

[1969CoronetR/T]

I have a 741 with 4.10 gears and a sure-grip that I need to sell, too.

 

[dvw]

I have a 741 with 4.10 gears and a sure-grip that I need to sell, too.

I didn't think they made 4.10 for a 741? I thought 3.91 was the end of the line. Did you count the teeth?
Doug

 

[1969CoronetR/T]

No, but I did the spin the wheel and count the drive shaft spinning and it was over 4 turns as far as I could tell. It may be 3.91 but in any case I went with 3.55 gears from Moser. It is at the transmission shop and the case has not been opened yet. I will have to count the teeth or see if the gear ratio is punched into the side. I hope I have the clutch type Sure-grip and not the cone type that I replaced with a Detroit Truetrac. Sorry to hijack the thread 528Wedge.

 

[Mopardaddy6969]

Ill take the 741 with the 410 gears

 

[1969CoronetR/T]

PM sent.

 

[Cranky]

Lets see. Sons 3800lb 62 Plymouth with a brake. Drag radials and a 3.23 8 3/4. Broke the sprag, then the pinion shaft and 90% of the ring gear teeth, then stripped the front planet. 3 pin planets, never hurt the planet gears, just stripped the hub. Installed an A&A super sprag, steel front planet and a junkyard Dana (used the 3.55 that came from the junk yard). Never an issue since.
Doug

Yup, that's where the pinion will usually give up the ghost. It doesn't matter what case it is from the 41 to the 89. They all use the same size yoke. The 89 might have a little less pinion gear deflection because of it's size but basically has the same strength at the yoke.

I didn't think they made 4.10 for a 741? I thought 3.91 was the end of the line. Did you count the teeth?
Doug

Probably factory gear ratio still.....?

 

[roccodart440]

By the time you spend enough to make the 8.750" last
you could get a Dana-60
or S-60 from Strange Engineering even better yet

From strange, a D60 set up for 1,000HP with disc brakes, powdercoated and all the bells and whistles was around 3200$. 8.75 was over 5,000.