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Re: Speedometers and Overdrive Transmissions

To: "S. L. Hower" <howersl@ttown.apci.com>
Subject: Re: Speedometers and Overdrive Transmissions
From: Craig Wiper <craigw@sonic.net>
Date: Mon, 14 Apr 1997 18:15:47 -0700
At 08:37 AM 4/14/97 -0400, you wrote:
>
>   Craig,
>
>   I wrestled my PC back from my wife.  Here's some data that I've compiled
>   over the years regarding the O/D swap.
>
>  I did a bit of research on the O/D swap and here is what I have found
>  from various sources (Bentley, Haynes manuals and A.B Bonds)
>
>  There were two types of O/D's fitted to an MGB (D type and LH type).
>  There are two types of LH overdrives ( Black label abd Blue label).
>  The LH O/Ds are interchangeable, but there are some gotchas:
>
>  The Black label is the 'early' LH; the Blue label is the later (~76 on).
>  The difference between them is the speedo gear *inside* the overdrive.
>  The speedo gears are rare and a royal pain to replace (O/D dissasembly).
>  Black label O/D trannys need a different O/D speedo (1280 vs 1000rpmile).
>  Blue  label O/D trannys and non O/D tranny's use the SAME speedo (~76 on).
>  Fitting a Blue label O/D tranny to a pre 76 car requires speedo 
>  recalibration (there is no pre 76 speedo that will work).
>  77-80 O/D trannys have O/D on 4th gear ONLY (the tranny remote tower is 
>  different).  
>  All MGB's from 68 onward use the same length driveshaft (31 1/8).
>  
>   (this last point has been debated somewhat)
>  
>  Please correct me if any of these are untrue!  
>
>  --Scott
>
>   Scott Hower  --> howersl@ttown.apci.com      
>   Air Products & Chemicals, Inc.        'Its better to be silent and
>   7201 Hamilton Blvd Trexlertown, PA     thought a fool than speak and 
>   (610) 481-2646                         remove all doubt' --A. Lincoln 
>
>
>
Hi Scott. I've placed the donor car's speedometer into my B. It is a
5321/04 1000. My old speedometer is a 5320/06S 1280. The overdrive is an LH
black label. I get the same results with both speedometers! The speedo gear
(plastic) is a white one w/22 teeth, same as the original which was stripped.
Craig Wiper     
craigw@sonic.net
http://www.sonic.net/~craigw

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