Rear axle parasitic loss

[V4F STR 60]

Well, the Montana Dodge Boys have decided to move ahead with building our V4F lakester for 2015.  Fabrication starts early next year.  I'm sure it's been tossed around here in forums before, but I can't seem to find any HARD DATA about rear axle and OD transmission parasitic losses.  I'm not looking for, "I once read", or "Sparky Smith told me", or "In Australia"...   because we all know pinions spin the opposite direction in the other hemisphere, right? 

We do not spin our motor fast, so we need an extremely tall gear...  taller than a 2.75.  BUT, at some point we will be going to V4 and then blown V4 at which time we'll spin another 1000+ RPM.  A blown XXO Chrysler will be on the horizon as well.  I mention this because it means we might need ratios between 2.0 and 3.5 in the next 5 years.

We initially were looking at a Winter's Xtremeliner because of the available 2.0 and 3.08 Ring and Pinion options, but they're stupid expensive and way overkill for a V4F.  The tech guy at Winters assured me that a V8 QC, even with the 3.78 R&P, would be more efficient than the Xtremeliner in our application.

We then thought about a Ford 9" like in our roadster, mostly because we already have ratios from 2.47 to 3.7, but from what I've read, 9" are awfully parasitic because of the low pinion position, and changing a pumpkin in a tank does not sound like much fun.

A salty veteran friend is hell bent on running an airshifted Liberty tranny with OD, but he must have more money than us.

I know Ford 8" are less parasitic than the 9" but we'd have to buy gears, and that doesn't address the issue of swapping it in a cramped tank.

I am leaning towards a Winter's V8 with 3.78 R&P, polished gears, and low drag seals & bearings.

So, here are the questions ~

1. Does a .8 OD tranny have more or less parasitic loss than a QC with a 3.78 R&P geared to a 2.5?
2. How much parasitic loss does the above QC have?  DATA please.
3. How does the parasitic loss of the above QC compare to other rear axle options (other options must have a drop out pumpkin)  DATA please.

Thanks for playing!  See you on the SALT!

[jdincau]

According to these sources a Hypoid (most popular third members) gear set is 92 to 96 percent efficient at power transmission. A spiral bevel (V-8 quick change) gear set and a single spur gear set are both 99 percent efficient. That makes a V-8 quick change 98.01 percent efficient . Tell me again why I should dump my quick change.

http://www.zakgear.com/Hypoid_worm.html

http://www.roymech.co.uk/Useful_Tables/Drive/Gear_Efficiency.html

[SPARKY]

7.5   2.14 2.28 2.56 2.73 2.92 3.08/ 3.08 3.23 3.42 3.73
8.5   2.41 2.56 2.73
10-12  8/78 (almost the same as Fords 8.  2.28 2.42 2.56 2.73 2.92 3.08

"The driving efficiency of an automotive hypoid gear is 92%-96%. Unfortunately the spiral bevel gear can not replace a hypoid gear in an automotive drive axle because it can not transmit as much of torque as a hypoid gear."

old Ford bevel gears are in the 98% range

GM axels are the 96%-95%  range the 7.5 being more efficient

Ford 9"  is in the 92%-91%

Virtually the only company still making car and light truck axels in the USA is American Axels--  spun of GM back in the 80-90s---the reason they are still around---better mileage in this day of mandated fuel economy because they are more EFFICIENT

[dw230]

Pedro,

A timely post to be sure. The White Goose Bar roadster is stepping up to a Winters for next season. As a result there is a V8-QC available with so many gear sets I can't count. PM me if interested and I will put you in touch with Greg Waters.

Merry Christmas,

DW

[jl222]

 Doesn't the Nascar Cup cars use the 9 in?

  Their fighting for every mph.

  JL222

[Peter Jack]

Rules dictate everything used on a Cup car.

Pete

[floydjer]

I`d be more concerned with the gear reduction you will lose with an overdrive.  Put a manual trans in 2nd gear and try to rotate it by the out-put shaft.  See what I mean ??

[jdincau]

Unfortunately the spiral bevel gear can not replace a hypoid gear in an automotive drive axle because it can not transmit as much of torque as a hypoid gear.

It depends on how much torque you need to transmit

[kiwi belly tank]

I`d be more concerned with the gear reduction you will lose with an overdrive.  Put a manual trans in 2nd gear and try to rotate it by the out-put shaft.  See what I mean ??

Yep, going through an overdrive to get to an underdrive before you get to the wheel.
  Sid.

[SPARKY]

it is all just high school physics ---eng. Torque x T rans. R atio x R ear Axel ratio X T ire Correction = Tractive Effort 

One is also dealing with the parasitic loss of each unit.  The rule of thumb use to be 20%  plus or minus for the whole drive train

[BobDcuda]

Sparky, how does the Mopar 8.75" compare with the Ford 9"?  About the same?

[SPARKY]

If it is a Dana it is in between the them  and if it isn't is still is most likely between them

[tauruck]

When I saw the subject the first time I thought someone else lost his
rear axle to a "Parasite" too.

[kiwi belly tank]

There ya go Bob, I recon Sparky just hooked you up with a definate maybe on that one.
  Sid.

[mike f]

Hi to all: You guys keep throwing around percent this and percent that on gears, but have you ever seen them on a spin-tron machine or a chassis dyno?   What is important and will tell you more is the coast down numbers they show.  I have yet to see a quick change rear axle have better numbers, also how the gears are built and type of bearings used have a great influence on loss.  I would find what ratios work and type you can afford then work from there.  Our Ford 2:30 ratios set a number of records this year on the salt but some quickchange gears also set records so again work within your means and find the little things that will help.  Hope all of you have a good X-Mas and New Year.   Mike   MF Performance