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MG MGB GT V8 Factory Originals Technical - T-5 Adapter to Smith's Speedo Cable?

What's a commonly used method of adapting a T-5's mechanical speedo drive to the Smith's type of cable?
I'm looking at machining the threaded end of the T-5's drive gear bushing and fitting a 90 deg. adapter from an old BW #65 Jag transmission but I'd welcome suggestions from those that have other ideas, thanks.
Anthony

Anthony,

The MG Guys make a converted MG angle drive which fits a T5 speedo gear. It looks like they turn an adapter collar to allow a GM threaded cap to fit the angle drive. It only fits the early style short housing w/ plastic shaft gear.

www.mgguys.com
207-884-8523 eve
207-884-7091 day
207-884-6159 fax

Joe
Joe Collins

Check out this link. It may help


http://www.geocities.com/v8mgb/speedometer.html
Jim Miller

Thanks for the tips, I'm now going to get an adapter for the T-5 machined for my speedo.
Anthony

An update: I had the male threaded portion of the BW T-5's speedo drive adapter turned down from 7/8" diameter to 3/4" diameter and a thread cut at 26 tpi to match the female thread of the knurled brass adapter ring from the old Jag BW-65 transmission's 90 deg. adapter. I then filed the square input drive tang of the 90 deg. adapter to fit snugly inside driveshaft of the T-5 speedo drive. The square tang had to be filed to a dimension of 0.110" across the flats to engage closely, it seems to work quite well.
Anthony

Anthony,just call Dan Lagrue at D&D Fabrication,he sells the speedo cables with the correct set up for both early and late speedos.The cables come with the MG fitting on one end and the larger T-5 fitting on the other,I think he gets $35-39 for it.
Dave D
Dave Deerson

Thanks a lot for the tip Dave but I'm fitting a modified Jaguar XJ dash and roll top in my car. I don't plan to use any of the original MG instruments, hence the interest in modifying a Jag's 90 deg. speedo drive adapter from a BW 65 auto transmission to work on a T-5 transmission. I'm using the donor XJ's speedo cable in this effort so I really only had the need for a "BW 65/T-5" adapter which my Dad just machined for me. He did a similar modification a while ago to drive the speedo in his "lumped" XJC, fitted with a TH700-R4 transmission.
Anthony

I went through all this when I was working out my speedo connection. I had access to 2 different years of MGB speedos, one which turn 1280 revolutions per mile and one which turns 1000 revolutions per mile (the most common). With my T5 I originally used the following information which allowed me to actually hook up the T5 to my speedo, but the speedometer was inaccurate.

The modification to the MGB angle drive is as follows.
Remove the female threaded ring from a GM cable. Remove the female threaded
ring from the transmission side of the MGB angle drive. (This is held in
place by a snap ring which is somewhat difficult to remove, an ice pick or
other pointed tool will help.) Enlarge the inner hole in the GM ring to fit
snugly on the MGB drive.
The squared drive tang from the angle drive must be ground down slightly to
fit into the GM drive gear.
Reinstall the GM ring onto the angle drive.
This might seem a little confusing. Let me know if you need further
information.
Bill

After this I spent a couple of weeks working out formulas and different gears trying to make the T5 gearing, rear end gearing, speedometer revolutions per mile and circumference of tires all work out so my speedometer was correct. No luck. What follows is some of that information for your consideration

Tag
10079856 GM# B2281 Serial #
13-52-176 BW # 15097 Built Date

Other numbers
By Gear shift lever 13-52-066-923R3 AWSF 1984
Passenger Side 13-52-065-914
Below is 231232450

1352-176 GM 1988 Car 103TBI 5.0l V8WC

Formula
Inch's per mile/rolling distance of tire = revolutions per mile x rear end ratio = revolution of drive shaft/speedometer gearing

A 63360/74.5=850.47x3.9=3316.8/1000=3.316
B 63360/74.5=850.47x3.9=3316.8/1280=2.59

2 drive gears in the Borg Warner T5 Blue 7 tooth and red 9 tooth
Available gears from GM 17-22 I currently have a 21 tooth read driven gear
Blue (Drive gear =7) Red (Drive gear = 9)
22/7 3.14 22/9 2.44
21/7 3.00 21/9 2.33 (Stock Camero)
20/7 2.857 20/9 2.22
19/7 2.71 19/9 2.11
18/7 2.57 18/9 2.00
17/7 2.428 17/9 1.88

This may not be anything new for some people on the list but I found a shop
that does custom speedometer cables and ratio adapter. They are familiar
with British cars and gave me the following pricing.

Cable - $30
Ratio Adapter - $49.95

With my application I have a
red drive gear (9 teeth)
and a red driven gear (21 teeth)
tires 185/70/14
Rear end 3.91
Speedo 1000 revolutions per mile

With this information I contacted the following people and the speedo is dialed right in. With all the information they should be able to make a right angled gear drive for any application.

ACI Engineering
Portage MI
616-327-1991
Tom

Good luck

Bruce

Bruce

Great stuff Bruce, thanks for sharing the detailed and very helpful information.
At present I have 7/19 speedo drive gears in the T-5 transmision, a 3.9 diff. and the XJ speedo is 1000tpm. I'll be adjusting ratios before the trans goes back in the car. Right now, I'm repairing a hole in the side of the tunnel where the shifter for a 4sp Muncie used to come through.....ugh.
Anthony

My pleasure.
When you get to that point contact Tom at
ACI Engineering
Portage MI
616-327-1991

They were good to me. There are probably other companies MG Guy's TSI and D & D who could help out as well.

Bruce
Bruce

This thread was discussed between 19/11/2001 and 29/11/2001

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