On Fri, 10 Jan 1997, Dave Clement-LDC009 wrote:
>
> From: elliott@serv.net@INTERNET on Thu, Jan 9, 1997 8:02 PM
>
> >BTW, that tranny is supposed to use ATF instead of gearlube. Could one of
> >our engineers explain to us dummies why ATF or engine oil is specified for
> >transmissions instead of gear lube? The only experience I've had with
> >engine oil in trannies was in 2 stroke dirt bikes, and using Bel-Ray gear
> >lube recommended (by Bel-Ray) to replace the engine oil REALLY helped
> >shifting.
>
> The motivation behind using ATF or motor oil in gear boxes is fuel mileage.
> Thinner oil produces less drag resulting in more mpg's. I found out the hard
> way that putting heavier oil in a gear box designed for a lighter oil does
> not work well. The gear box in my Shelby Daytona specs 5W-30, being that I
> have a mental thing that heavier is better I replaced the oil with 20W-50
> and the gear box shifted like sh*. I was back under the car the next day
> draining it and refilling with 5W-30.
>
> NOTE: As I recall from MX days the Bel-Ray and Spectro gear box oils were
> still a fairly light weight, on the order of 30W to 50W. Also, there are no
> syncros in a motorcyce geasr box.
>
> Dave Clement
>
Somewhere I've got a viscosity chart that shows the equivalence between
SAE engine oil and gear oil numbers with Saybolt Universal Seconds (SUS).
As I remember SAE 30 engine oil is about the same as SAE 90 gear lube in
SUS, why the SAE viscosity numbers are different is beyond me, maybe to
keep people from using gear oil in engines and wrecking the plain
bearings. As I remember the Bel-Ray oil that was supposed to replace
10W-40 in the PE 175's gearbox was 75W. It was pretty thin and greatly
improved the shifting, snick, snick, snick instead of crunch, crunch,
crunch.
From trying to pour straight SAE 40 or 50 wt engine oil and SAE 75 to 90
gear lube at similar temps I can testify that the engine oils were a lot
more viscous than the gear lubes.
Larry
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:07:30 EDT