Rear end efficiency

[Joe Timney]

A bigger issue is R&P break-in. Mike Powell who used to own Tex Racing, a major Nascar Trans and third member supplier, has done extensive testing of 9 inch Ford gear sets...he stated that it took 70 laps on the Daytona track to break-in the R&P. I do not remember the  HP loss. He developed a rear third member break-in machine but moved to REM'ing the gear sets because it was so more efficient. Rem'ing is an electro-polishing process that removes the tool marks from the gear faces...they come out like they are chrome plated. I always suggest to my customers to get the REM option. After all, it would be a lifetime breaking in your R&P at Bonneville.

[38flattie]

Sparky,
     It is a Halibrand, they were based on the 32-48 Ford ring and pinion. That's why they called it a V-8 as opposed to the older model A quick change which had no bearing on the pinion snout. The pinion is centered on the ring gear. Mind you I wouldn't want to push more than 600 HP through it. The later champ car quick change is based on a late 40's Ford truck rear end also having the pinion centered on the ring gear will take up to 800 HP. I have no Idea which ring and pinion the later Winters and Speedway types use.
Jim

So does the Champ have more parasitic loss then the GM rear end? I would think it would.

How about the Frankland's? They were based on the 32-48 Ford, correct?

[Peter Jack]

The quick change gears are what cause the extra loss in efficiency.

Pete

[doug odom]

OK, We have been down this road before.  I did back to back to back testing on a dyno. My 3 LSR cars have 2 Ford and 1 quickchange because that is what fits the car best. Your pounding sand in a rat hole if you think there is any real difference in the amount of power loss between a quickchange and ford 9 inch.

[John Burk]

The friction loss at Bonneville for any type rear is 1% - 1.5% . Use what fits best or has the best ratios .

John Burk

[Peter Jack]

I'll happily go along with that.
It's so much easier to change ratios in a quick change, although a 9" with floaters isn't bad.

Pete

[38flattie]

The friction loss at Bonneville for any type rear is 1% - 1.5% . Use what fits best or has the best ratios .

John Burk

That's great! I just needed it confirmed!

[Dan Stokes]

I'm remembering the old Hi Lux Toyota pickups had positively retained axles and a drop out center section - basically a scaled-down 9".  Not that the Japanese would reverse-engineer anything!  Anyhow, other than gear selection (no clue what's available) that might be a pretty decent choice.  I don't remember anyone having trouble with them and I know some had SBCs installed.  Seems like the parasitic loss would be relatively low - but I'm guessing.

Dan

[38flattie]

I decided on a GM 7.5", as it should be pretty efficient, and a Watts/4-link seup.

My question is, how is everyone limiting the 'up' travel? I undersytand that I need very little, if any.

[Peter Jack]

Use stiffer springs. Never limit travel with any sort of positive stop. If you must, use some sort of resilient pad so the stop is not so much shocked. Any sudden change in spring rate leads to a sudden change in handling characteristics and that's never good.

Pete

[krusty]

On our coil over shocks, we limit bump (compression) travel with bump stops on the shock shaft. These stops are not solid, and allow an increasing rate of resistance as they rise against the shock body. They are available in different rates. To set the bump stop height, we place "packers" (NASCAR talk, sorry!) between the bottom of the shaft and the bump stop. A packer is a round piece of hard plastic with a slot in it which allows the packer to be easily slid on to the shaft (so you don't have to undo the shock shaft eylet to make height changes). Packers are available in different thicknesses, and can be stacked on each other. We limit droop (rebound) travel by using the bump stops (attached to the frame) from a pair of traction bars under the axle tubes and adjust them by shimming to the correct height.    Hope this helps.     vic

[Nexxussian]

Dan S, Toyota had a similar axle that as far as I know is still being used by the Legends Cars and Thunder roadsters.

It's the 8" Toyota (RWD Celica).

Last I saw there were new housings, axles, gears and carriers available (open, spool and various types of Limited slip).

That was 6 years or so ago, so it's hard to tell what's available now.

Gears were available from somewhere in the mid 4's up to 2.50; IIRC from Richmond.

[johnneilson]

I think Strange is making an aluminum center section to fit into the Ford 9in housing that takes GM 12 bolt gears. The 12 bolt gear CL is closer than the Ford.
Anyone with experience on this?

John

[Meteor]

I'm running a 9" Ford because of availability of gear (2.50) and strength. But, an 8" Ford is just as strong.  Nothing common below 3.00 for ratio though. 8" were common in the 69 Mustangs and up through the early 80's.

No an 8 inch is not as strong as a 9inch Ford rear, I have shattered 8" with 3:50 gears and 300 hpat the wheels. Way more than once, have tried open rear and posis. If you could find a spool then it would be ok maybe, but spool is drag race only.

[Peter Jack]

Meteor, just so you know spools are very common in both oval track and on the salt. In oval track they use tire stagger to compensate, that is a larger circumference tire on the right side than on the left. At Bonneville it's really important that both tires have the same roll out. On the salt the common feeling seems to be that if you're spinning out with a spool try an open rear end and if you're spinning out with an open rear end try a spool. It seems each car and driver combination is different. The "Gleason type" rear ends are also popular.

Pete