8 3/4 Chrysler pro gears?

[Myron Piatek]

Originally Posted by Coleydog

All this bad vibe has made me change direction, going with Dana instead. Always heard the 8-3/4 was more efficient.

I read a dedicated article comparing rear end efficiency in one of the old car magazines a long time ago. Of the rears that I remember they tested, this was the order of efficiency:

1) GM 12 bolt
2) Dana 60
3) Chrysler 8 3/4
4) Ford 9"

I believe it said that the biggest factor is the placement of the pinion in relationship to the ring gear. The higher the pinion (closer to center), the more efficient it is. The 9" has the additional disadvantage of an extra pinion bearing.

I don't recall what others were tested.

Somebody makes/made a 12 bolt style center section for 9" housings. Was it Jim Kinnett that had a 12 bolt or a Chrysler 9 1/4 rear in his SS/AA Cuda?

[Jim Wahl]

Originally Posted by Myron Piatek

I read a dedicated article comparing rear end efficiency in one of the old car magazines a long time ago. Of the rears that I remember they tested, this was the order of efficiency:

1) GM 12 bolt
2) Dana 60
3) Chrysler 8 3/4
4) Ford 9"

I believe it said that the biggest factor is the placement of the pinion in relationship to the ring gear. The higher the pinion (closer to center), the more efficient it is. The 9" has the additional disadvantage of an extra pinion bearing.

I don't recall what others were tested.

Somebody makes/made a 12 bolt style center section for 9" housings. Was it Jim Kinnett that had a 12 bolt or a Chrysler 9 1/4 rear in his SS/AA Cuda?

Kinnett ran a 12 bolt GM rear in both the Hemi SS car and the Pro Stocker. I have seen them both personally. Jim

.

[Bob Mulry]

Originally Posted by Myron Piatek

I read a dedicated article comparing rear end efficiency in one of the old car magazines a long time ago. Of the rears that I remember they tested, this was the order of efficiency:

1) GM 12 bolt
2) Dana 60
3) Chrysler 8 3/4
4) Ford 9"

I believe it said that the biggest factor is the placement of the pinion in relationship to the ring gear. The higher the pinion (closer to center), the more efficient it is. The 9" has the additional disadvantage of an extra pinion bearing.

I don't recall what others were tested.

Somebody makes/made a 12 bolt style center section for 9" housings. Was it Jim Kinnett that had a 12 bolt or a Chrysler 9 1/4 rear in his SS/AA Cuda?

Hi,

Strange still manufactures an aluminum 12 bolt drop out center section that fits into a 9" Ford housing........

I wonder if that will pass tech (HA HA) for a GM Stock Eliminator car?????

Just sayin'

[SSDiv6]

Originally Posted by Bob Mulry

Hi,

Strange still manufactures an aluminum 12 bolt drop out center section that fits into a 9" Ford housing........

I wonder if that will pass tech (HA HA) for a GM Stock Eliminator car?????

Just sayin'

Bob,

The Strange 12-Bolt, 9" drop out has weight limitations on its use.
It's designed for very lightweight cars, dragsters and roadsters.

[Bob Mulry]

Originally Posted by SSDiv6

Bob,

The Strange 12-Bolt, 9" drop out has weight limitations on its use.
It's designed for very lightweight cars, dragsters and roadsters.

Do you want stuff to live forever??????

Look at all of the "Stock" cars that run lightweight front disc brakes for "safety"

Usually light duty is fast, at least for a while.......

[Dwight Southerland]

Originally Posted by Myron Piatek

I read a dedicated article comparing rear end efficiency in one of the old car magazines a long time ago. Of the rears that I remember they tested, this was the order of efficiency:

1) GM 12 bolt
2) Dana 60
3) Chrysler 8 3/4
4) Ford 9"

I believe it said that the biggest factor is the placement of the pinion in relationship to the ring gear. The higher the pinion (closer to center), the more efficient it is. The 9" has the additional disadvantage of an extra pinion bearing.

It's called hypoid distance. Dana 60 is 1.125". MoPar 8 3/4, GM 12 bolt and 10 bolt, AMC Model 20 are 1.50". Ford 9" is 2.25". The farther the pinion is from the centerline of the ring gear, the greater the angle of the drive teeth to the ring gear teeth and more friction. Bearing size is a factor for efficiency as well as rotating mass.
I remember that same article, but have since learned from other sources who have done serious experimentation that the Dana 60 is more efficient than the 12 bolt.

[SSDiv6]

Originally Posted by Dwight Southerland

It's called hypoid distance. Dana 60 is 1.125". MoPar 8 3/4, GM 12 bolt and 10 bolt, AMC Model 20 are 1.50". Ford 9" is 2.25". The farther the pinion is from the centerline of the ring gear, the greater the angle of the drive teeth to the ring gear teeth and more friction. Bearing size is a factor for efficiency as well as rotating mass.
I remember that same article, but have since learned from other sources who have done serious experimentation that the Dana 60 is more efficient than the 12 bolt.

Dwight is correct; after much analysis, the final result is the Dana 60 is the most efficient of the bunch.

[Coleydog]

Originally Posted by SSDiv6

Dwight is correct; after much analysis, the final result is the Dana 60 is the most efficient of the bunch.

Maybe someone will make more ratios again. Picked up another Dana housing yesterday, free

[Todd Boyer]

Originally Posted by Myron Piatek

I read a dedicated article comparing rear end efficiency in one of the old car magazines a long time ago. Of the rears that I remember they tested, this was the order of efficiency:

1) GM 12 bolt
2) Dana 60
3) Chrysler 8 3/4
4) Ford 9"

I believe it said that the biggest factor is the placement of the pinion in relationship to the ring gear. The higher the pinion (closer to center), the more efficient it is. The 9" has the additional disadvantage of an extra pinion bearing.

I don't recall what others were tested.

Somebody makes/made a 12 bolt style center section for 9" housings. Was it Jim Kinnett that had a 12 bolt or a Chrysler 9 1/4 rear in his SS/AA Cuda?

I remember reading that Rick Johnson ran a 9 1/4 Mopar rear in his SS/AA Barracuda at one time. He may still.

[Rod Greene]

DeFrank and Cohen had a 9 1/4 in their AA Cuda. I remember looking at it during a points race at Irwindale in the 70's.

There have been many articles about the low drag of the Dana 60. there was an article in one of the Mopar magazines where they took out the 8 3/4 and back to backed it with a Dana 60. the Dana was almost a tenth quicker even with the added weight. If you use the right parts you can get a Dana within 15 pounds of a prepped 8 3/4.