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MG TD TF 1500 - Gear Question....

When considering changing my rear end gears, i checked the archive and came up with a listing for various ratios....sorry, i didn't note the poster:

ring gear teeth pinion teeth

39/8 =4.555
41/8 =5.125
39/9 = 4.333 MGA
41/10 =4.1 1962 MGA

I just got my gears from my friend in Ottawa today and counted.... 42/10 ??? He said they came out of an MGA... anyone know why i have 42 teeth?

gordon lawson - TD 27667

Maybe you counted wrong? ;)
David DuBois

Counted 3 times....honest!
gordon lawson - TD 27667

Gordon - On a more serious note, I checked my CD that has the Magnette data on it, thinking that it might be there. Unfortunately it has 39/8 and a 41/9 but no 42/10. You might hop over to the midget BBS and ask if that matches anything that they have. Good luck - Dave
David DuBois

Oops - Just thought, My Magnette info is for the ZA and ZB, you might also try the Magnette BBS and ask about the Farina Magnettes. Cheers - Dave
David DuBois

Gordon,

Ther "MGA" back axle was fitted to a whole range of BMC cars including the Morris Oxford, the Austin Cambridge and Riley and MG variants. There was even an Austin van. Unfortunately I don't know the teeth numbers but is is quite possible there is one with 42 teeth.


Cheers


Jan T
J Targosz

My concern isn't actually number of teeth...I think a 4.2 would be fine (have read that some have installed a 4.1 without problems 'well, a large hill might be a problem'), but that it will able to machined and fit....?
gordon lawson - TD 27667

Gordan, you've somehow missed a very common set that many of us have installed, the 4.3 ratio (43/10). In his treatise on the topic, Carl Cederstrand lists the following as available to fit the TD/TF rear end:

TD/TF: 8/41 (5.125); 8/39 (4.875); 9/41 (4.555)
MGA: 9/41 (4.555); 10/43 (4.300); 10/41 (4.100); 11/43 (3.909).
Bud Krueger

The only machining needed for any of the MGA, or early MGB (3.909/1) gears is to the pinion spacer washer.
Note that the ratio (41/10, etc.) is stamped on the "chunk", look for it to confirm your count.
I also think you must have miscounted unless you have a non-austin/morris rear end (then all bets are off on whether it will fit the T)
Don Harmer

Power transmission gears should NEVER have a common factor, as in 42/10 where there is a common factor of 2. This is to equalise wear over all teeth. (there may be exceptions, but it is bad practice, and I don't think any MGs violate the rule) 2 of the 4 number/ratio sets Gordon quotes are wrong, but the Cedarstrand/Krueger numbers are good. The tooth count for the set should be stamped on the gears, certainly it is on the ring, but I don't have a pinion out to look at.
Gordon, are the gears loose or is it assembled? The gears must be a matched/mated pair. This means that even if you have two sets of, say, 43/10, you can't switch the gears between pairs. And the 10 from a 41/10 set is NOT the same as the 10 from a 43/10 set.
FRM
FR Millmore

I agree with FRM about 42/10 this is a poor design, a proper set of gears should have "hunting teeth", that is an odd ratio such that two given teeth mesh infrequently. Good luck,
w.g cook

Damn, damn, damn... ok.... so there are actually 43 teeth and 10 on the pinion...
(it must have been the '70's that did it.... i seem to remember the 70's... i think i remember...they came after the '60's right????)

David, you win....!!!!!!
gordon lawson - TD 27667

http://www.niagarabritishcarclub.org/otr/td209.jpg

http://www.niagarabritishcarclub.org/otr/td210.jpg

http://www.niagarabritishcarclub.org/otr/td211.jpg
gordon lawson - TD 27667

Gordon,

If you counted 42 three times and now one time a lucky 43, statistically you're still 3/4 teeth down? I'd count again....
Willem van der Veer

Gordon,
" i seem to remember the 70's... i think i remember"...........
If you "know" of the 70's ...you were there. If you "remember" them...you did not participate! ;-)!
Cheers,
David 55 TF1500 #7427
David Sheward

Sorry, Gordon - I also counted 43 and 10 - only took me one shot ;-) (but I've also had several cups of coffffeeee thhhis a.mm. so I mmight havee miscountedddd ;)

Larry
Larry Thompson

You know, it is so much easier to count gear teeth if you mark the one you start with...

I learned that from an old dentist...

dave
D. A. Braun

This thread was discussed between 02/06/2005 and 03/06/2005

MG TD TF 1500 index

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