Rearend suggestions please

[Herr_Poopschitz]

I'm finishing up the chassis work on my 67 Plymouth sedan and going to be starting on the engine phase soon, but not sure which way to go on the rearend. Currently have an 8 3/4 w/ 3.23s...489 case if I remember correctly. I'm planning a 575ish hp 440 w/ a TKO 600. I've read about many people using the 8 3/4s in full weight cars going mid/high 10's so they seem capable...but all of these are autos w/o 'brakes, and wondering if the manual trans will be that much more violent and potentially causing breakage.

I plan on running 295/45 18's most of the time, w/ prob a 275/60 MT Drag Radial when I want to have some fun...intend to run a 3.5x or 3.73 gear in whatever I end up w/. The car is all steel, full interior, leaf sprung, w/ the normal aluminum stuff on the engine as being the only 'weight savings'.

Am I at the limit of the 8 3/4, and might it be smart to step up to a Dana or 9"? Just want to do it once.

Thanks for any advice.

 

[wedge69]

I don't see why the 8.3/4 won't work. Its a tuff rear for sure .

 

[themechanic]

I'm sorry but I just had to laugh when I saw the irony of your post. Herr Poopschitz needs help with his rear end.

I'm no expert but I think the 8 3/4 489 case should be fine on the track assuming it's a posi.

 

[Budnicks]

Properly set up the 8.75" can handle quite a bit, truss the back of the housing, use good hardware, get good aftermarket axles to be safe, a good diff or locker it should do pretty well {maybe also a nodular iron 489 or alum. 742 carrier}... I ran in the mid 9's N/A with a 727tf {went mid 8's with N20} with a 3250# 68 RR for 7 years with a 742 Carrier & Richmond Pro Gears, Mark Williams Axle IIRC... All my 4spd or Manual trans &/or Lenco/Jeffco cars either had a Dana-60 or a 9"... Not really what you want, but I did run a 8.750" center & Carrier, solid mounted, with full floating Lenco axles & ends w/spool in my 1600-lbs {1850-lbs with me in it} Altered for a while, I was trying to keep it as light as possible, it held up-to 1800hp Blown alky combo, Crowerglide & a Jeffco 3 speed, 33"x17" Hoosiers, 5500rpm launches, never broke it & they are allot tougher than some people give them credit for... IMHFO if you want it to be pretty much Bullet proof & do it basically only once, then I suggest to go with the Dana-60 {like a S-60 from Strange}, or even a Ferd 9" from Currie, by the time you spend the money to make a 8.75" strong enough, you can have a Dana-60/S-60

 

[Cranky]

Looks like we're back to how much do you want to spend on an 8 3/4 to make it as strong as a stock Dana 60 Before I ever spend that much time or money on an 8 3/4, a Dana 60 will get the nod. Run the 8 3/4 as it is and if you break it then get rid of it or, sell it and put the money towards the 60. It takes nearly a whole hand to tell you how many 8 3/4's we scattered on the track running low 11's-mid 10's with a 4 speed launching at 6k.....and after that, a bone stock (except for a spool) 60 took it's place and we never looked back that is until many many month later when the tech guy finally noticed we didn't have aftermarket axles for running 10's. The only benefit to a 9 is gear selection because you need to modify those too to take the abuse of a stick. And the thing is, the 8 3/4 will never be as strong as the 60....

 

[Budnicks]

. The only benefit to a 9 is gear selection because you need to modify those too to take the abuse of a stick.....

:iamwithstupid: they have a rear pinion support & bearing too, but a nodular case & beefed up, housing too, is also recommended on a ferd 9", Money & speed are relative how much do have to spend goes hand & hand with how fast you want to go...

 

[Herr_Poopschitz]

I was worried this topic had been beaten to death, but I couldn't find anything specific w/ respect to how they live in (higher) hp stick shift applications.

S60 it is.

Thank you gentlemen.

 

[Cranky]

:iamwithstupid: they have a rear pinion support & bearing too, but a nodular case & beefed up, housing too, is also recommended on a ferd 9", Money & speed are relative how much do have to spend goes hand & hand with how fast you want to go...

That bearing support doesn't do much as there's not much meat there at all. The first time I saw one opened up, I thought why bother lol. Also, the 9 eats a bit more horsepower than either the 8 3/4 or the 60 but another benefit is that it's a bit lighter than the 60 but weighs more than the 8 3/4. Also, not all 9's have the heavier/stronger case and when I see the pinion gear pulled out of it with the pinion adapter still attached with bolts....well....that's a sign of the one with the weaker case lol

 

[Meep-Meep]

Good choice. I'm going S60 or modified truck 60 in my green Bel at some point.

The stock 9" carrier is not that strong so if you do anything with those you will want a billet carrier.

 

[65hemi]

When I put my Cuda together my engine guy laughed and said the 8.75 would be fine as long as I did not get traction. I went with a modified truck 60 from Dr Diff. I have put an S60 in my 65.

 

[Endangered Species]

If I were starting from scratch and wanted to do it once, I would go with the Strange or MW Dana 60 or a Ford 9". If you have the 8.75 you can get it to hold up to quite a bit of power but you'll end up bracing the housing and tubes, M/W or Strange Axles etc etc...

 

[snakeoil24]

Properly set up the 8.75" can handle quite a bit, truss the back of the housing, use good hardware, get good aftermarket axles to be safe, a good diff or locker it should do pretty well {maybe also a nodular iron 489 or alum. 742 carrier}... I ran in the mid 9's N/A with a 727tf {went mid 8's with N20} with a 3250# 68 RR for 7 years with a 742 Carrier & Richmond Pro Gears, Mark Williams Axle IIRC... All my 4spd or Manual trans &/or Lenco/Jeffco cars either had a Dana-60 or a 9"... Not really what you want, but I did run a 8.750" center & Carrier, solid mounted, with full floating Lenco axles & ends w/spool in my 1600-lbs {1850-lbs with me in it} Altered for a while, I was trying to keep it as light as possible, it held up-to 1800hp Blown alky combo, Crowerglide & a Jeffco 3 speed, 33"x17" Hoosiers, 5500rpm launches, never broke it & they are allot tougher than some people give them credit for... IMHFO if you want it to be pretty much Bullet proof & do it basically only once, then I suggest to go with the Dana-60 {like a S-60 from Strange}, or even a Ferd 9" from Currie, by the time you spend the money to make a 8.75" strong enough, you can have a Dana-60/S-60

its only Money. The dana or the 9 inch will wind up being cheaper than modifying the 8 3/4 Don't get me wrong the 8 3/4 is fine. But the Dana is a Truck Rear and the Ford engages three teeth on RIng with Brass balls sized end bearings. Do it once in the following order 9 inch ford or Better is Dana 60 not a Strange S 60.

 

[robinsonwr]

I would stay with the 8.75. The 489 case boasts pinion bearing sizes larger than the 9 inch anyway. The 9 inch is preferred by a lot racers because the abundance of aftermarket parts.

 

[moparcardave]

Agree, stick with the 489 with the suregrip. It has the thickest pinion shaft and is plenty strong. Have owned about 20 old mopars and never ever had a problem with them. I wasn't very easy on them either.

 

[brian.linn]

I would suggest cutting down a truck Dana with a spool, bullet proof and cheaper than buying a performance third member.... There is a guy in the ICT area that did these back in the day, not sure if he would do it, but I did mine for about $700 which included new Strange Axles, spool, bearings and seals... Very happy with it... PM me for more info...

 

[hemi-hunter]

the factory used a Dana 60 when a 4 speed was ordered, they knew then the 83/4 limitations. A 9 inch ford with a strange center section pro gears and 33 spline axles with a strange spool you will never look back.

 

[69 GTX]

I'd say if you never go to the strip 8 3/4, but if you plan on slicks or the drag strip go with a Dana. A wrinkled rear quarter or front end isn't worth it.

 

[Cranky]

Agree, stick with the 489 with the suregrip. It has the thickest pinion shaft and is plenty strong. Have owned about 20 old mopars and never ever had a problem with them. I wasn't very easy on them either.

It's not the pinion that presents problems but the teeth getting shaved off the ring when the pinion tries to climb it. How many pinion shafts have you seen broken? Even the 41 case has a good strong pinion gear and it looks like a wimp next to the 89 pinion. I've never broke a pinion but have shaved the teeth off of several ring gears and all of them were 8 3/4 rears.