Rear end efficiency

[mtkawboy]

I have an 87 Toyota 4x4 pickup with 4.11 gears and a 2007 2 wd Tacoma with 3.36 gears. Not trying to sell anything, just advise you to whats available. Almost all the newer Tacoma 4x4s are 4.11 geared

[JimL]

Looking through the posts, I realized I didn't explain how they design the rear diff for high load or low friction.  If you look at the ring gear width (and pinion teeth longitudinal length) you'll see that the "low drag" units are MUCH narrower than the high load setups.  Many will have a little less helical shape (pickups particularly can live with this, because the diff noise "usually" doesn't get into the cab).  We do have to use cardboard liners in the driveshaft tubes to prevent "ringing" or "whistling", with the flatter helicals.

For example, one of my favorite axles is the 47" (backing plate to backing plate) Hilux 8".  I have built these using Supra Turbo 4-spider LSDs by hand plunging the races on aftermarket Timpken bearings (to fit the smaller bearing clamp in the truck housing).  Pinion tooth and ring tooth engagement is about 1/3rd longer than the standard truck parts.  You can definitely feel the difference just spinning them by hand....BIG teeth.

Dan Wagner and I ran the 8" Hilux in our 2-liter roadster....many runs around 175-180 with no problems.  My boss runs the same axle in his V4F/Street Roadster; saves a few horses....using gears from 4-cylinder trucks.  Lots of this stuff in the pick-a-parts...usually about $75-100.  For low power cars, look for the skinny gears and you'll be fine.  NOTE:  The Taco parts don't swap into the old housings, though you can go the other way.  Taco axle is very wide, for most of our cars.

Don't forget....CHECK SIDE GEAR CLEARANCE on high mileage diffs.  If one is worn more than the other, you'll be trying to drive the right and left wheels at different gear ratio, because the engagement will be too shallow and the diff will "make up the difference", so to speak.  It'll tend to get one wheel "loosened up" because the other is following behind the power applied....makes the driveline groan going down the road....we see this on the old "trashed out, bottom feeder 4x4s" that ran with a mix of giant tires, worn out.

Hope this helps.
JimL

[salt27]

Does anyone know how the old pontiac/olds diff's compare to a 12 bolt for parasitic loss? How about the 8 3/4 mopar.
Thanks Don

[jimmy six]

Olds/Pontiacs have a higher pinion placement than the Ford or non pumpkin GM making them more efficient. Their highest available axle ratio is 2.56. They are alot more than the $20 they used to be....JD

[salt27]

JD;
Thanks for the info. I've got a couple of them stashed away, maybe thats what i'll use.
Don

[SPARKY]

The caddy10-12 or 8 7/8" have a 2.41 and a 2.28  they are usually found in 77-78 Fleetwood Broughams with disk rear brakes and have
C-clips

[Dean Los Angeles]

Does anybody have hard numbers? The quote below states 6-10% losses through the differential.

I'd sure like one of them there 6 percenters stead o' the 10 percenters!!

Most rear drive cars have a 1 to 1, 4th gear which means that the power path goes directly through the mainshaft of the transmission. The only losses here are bearing drag which is less than 0.5% and the viscous drag of the gears running through the oil which is about 1% with hot oil. Indeed, published data indicates a transmission efficiency of 98 to 98.5% for conventional transmissions in 4th gear.

Losses within the driveshaft account for about 0.5% if they are properly aligned, balanced and with fresh U-joints.

Differential losses in the commonly used Hypoid type gearset is in the order of 6 to 10%.

[John Burk]

Dean

The friction loss in a rear is easy to estimate if you know the gain in heat during a run and how much metal and oil was heated . Steel takes .12 BTU to heat 1 deg F , iron is .11 and oil is about .5 . If the part of a 9" rear that gets hot weighs 100 lbs every degree it heats up is roughly 12 BTUs . If it gains 40 deg that's 480 BTU . 1 HP for 1 minute is 42.4 BTU so 480 BTU in 1 1/2 minutes is 7.55 hp . For 500 hp that's 1.5% . The numbers like 6% that you commonly hear are probably at 50 MPH when the engine is putting out 20 HP.

John

[SPARKY]

Dean,  The Ford has the most drag -- then Dana then GM then EArly ford---its BEVEL  total spread 5-6%---dont have "facts" in writing---just drive train engineers from GM  and Pyle Brothers in Baytown---who set up a TON of all different tyes or gears

[panic]

How much power is lost through churning lubricant around, as opposed to a re-circ system that puts it back directly onto the tooth engagement?

Other than measuring tooth contact (or a series of loud clank noises), how do you know when the fluid is too thin?

[salt27]

I remember reading a article about a fellow who designed a ring and pinion that had cogs on bearings instead of teeth. His purpose was less friction for better fuel milage. It was installed in a s-10 pickup sometime in the 80's. Does anyone else recall this?
By the way JD as far as $20 Olds/Pontiac rear ends go, how old do you think I am, I've never seen them less than $25.
Don

[dick elliott]

83/85 RX-7's have a posie / 3:90 - 4:10 gears / disc brakes and are plenty strong.

[836dstr]

Hey timing is everything!

I'm on this thread, the phone rings and it's Mark from Pro Gear here in San Diego. I'm having a new third member made up for El Mirage.

One thing Mark pointed out not mentioned here, or I missed it, is the higher centerline of the pinnion in early Olds/Pontiac is offset by the mass of the ring gear. He also said their studies show an average loss of about 3% and talked about all sorts of exotic things that can be done to components. How much do you want to spend(like $200 each for ceramic coated bearings, or cutting down the front and rear of the gears on the pinnion)?

Another point Mark made was that most LSR cars run open rearends. I didn't realize that. I currently run a Posi 9" that has worked good, so far.

Tom

[SPARKY]

GM 7.5 series 2:

2.14, ( 2.23 I have heard), 2.28 2.41 2.56. 2.73 -2.75 (mabye 2.9 ) and 3.08 also availabe with Torsen carriers from camaros with 28 spline.

[gnx7]

I have a friend drag racing a mid 90's Toyota Pickup truck and he runs the stock 8" rear end with an off the shelf spool setup and stock axles.  It runs a single turbo PT88 274ci Buick V6 T/A aluminum motor/TH400 and is hitting high 8's without any issues.  He is making around 1000hp. The truck weighs approx 3300lbs and can drag the bumper for as long as he wants.  He has since switched to a 532ci BBC running 2 PT88 turbos for 2010 to add weight to the front to help keep it planted and obviously go deep in the 8's if not 7's.
http://www.youtube.com/watch?v=JkyywX7YqBM&feature=related

There are a number of gear ratios available for this rear from Toyota.  That should be on your list as well.