Instead of lifting both rear wheels, just lift one side. The result
is out by a factor of two, but that is easy to compensate for!!!
If you lift both wheels, you can get errors by one wheel dragging on
brakes.
Also, if you only lift one wheel, you can do it by yourself...
Mike
-----Original Message-----
From: Michael Graziano <mgrazian@ltcm.com>
To: MGList <mgs@autox.team.net>
Date: Tuesday, June 23, 1998 8:16 AM
Subject: Differential Calc
>Hello all. I'm still trying to figure out why my Midget is
>topping out at 50 mph at 4500 rpm. THanks for all the
>suggestions so far. While none have solved the problem
>yet, you have all moved me along the learning curve quite
>rapidly.
>
>I've narrowed down the problem (I think) to my
>differential.
>
>The car still has plenty of pep at 50 mph, so I know it's
>not something like carb, valves, exhaust, etc.) It's simply
>bound by the little red section on my tach.
>
>The clutch isn't slipping (it's new, and I'd be able to
>tell if it were slipping that much).
>
>And I've made sure my gauges are correct by having a friend
>driving next to me to check the speedometer, and by using a
>tach/dwell on the tach. Right on until 4000 rpm when the
>meter tops out (the gauge increases steadily after 4K).
>
>SO it must be in the drive line. I thought maybe it was
>possible for someone to have rebuilt the tranny with the
>wrong gearing (thanx Bob for straightening out that
>misconception). What's left? The differential.
>
>I know the PO (quickly becoming an ignorant DPO) changed the
>differential because one of the bearings (somewhere) had
>worn, but he didn't know what gearing the new (used)
>differential was. Yes, I called him this weekend. I even
>called the mechanic who installed it, entertaining a slight
>hope that he might have a) remembered where he got the used
>one (it was only 6 or 7 months ago), or b) he actually kept
>records. Negative on both (duh!).
>
>Now the question ..... How can I tell what the gearing in
>the differential is? I tried jacking up the car by the base
>of the differential (so both rear wheels were free) and had
>2 friends turn the wheels at the same rate while I counted
>how many times a little white dot moved around on the drive
>shaft per wheel revolution, but either they were inept at
>turning the wheels synchronized, or I was inept at counting
>the white dot. End result: Aggravation and a wide range of
>results. I wasn't even close. THere has to be a better
>way?
>
>Any insights on any of this? My next step is a mechanic
>(God Forbid) because I HATE watching grandma in her 85ish
>corolla with blue smoke coming out the tailpipe giving me a
>dirty look as she passes me like I'm going in reverse, (True
>story, BTW).
>
>Mike
>
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