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MG MGB Technical - Reverse gear teeth wear

I have pulled the transmission out of a '79 MGB to sell it to an individual whose tranny went completely out. This is a standard all synchro four speed with no O/D. Upon taking the side plate off of my tranny I noticed that the reverse gear has some tooth wear on the sides (or ends) where they begin engagement. I'm sure this is from years of former owners grinding the transmission into reverse. Only a small portion of the leading edges of the gears is worn, but it is defintiely evident. My question is, how much wear is normal?

Are other years of MGB four speed synchro transmissions the same as this one? I have another in a '69 that I might sell to him, but the car it's in also has an engine that will require pulling. This '79 had no engine to get in the way, so it was simple.
Chuck Asbury

Scared to look. Ignorance is bliss when it comes to impending failure.
R. L Carleen

The reverse gears generally have a fair amount of wear; not to worry if reverse worked and didn't make odd nosies. The straight cut gear whine is normal.
Leland Bradley

Ignorance isn't bliss when it comes to selling faulty used parts. It's stupidity. Would you want to do all the labor associated with installing a bad transmission only to have to do it again Mr. Carleen? I don't want to do that to my friend who's buying it. I'm of the opinion that nearly every MGB transmission with 25 years of wear probably looks the same as this one, but I want to hear it from someone who has actually been there and done that.
Chuck Asbury

Chuck -
The engaging ends of the reverse idler teeth have a lead in taper, dont confuse this with wear.

Some minor chipping on the ends on a used one is not unusual, and dosn't make the gear u/s.

Look for major chipping in the ends of the teeth, and loss of hardening on the tooth flanks.

Ditto for the cogs that the idler engages with.

Cheers
ian F



Ian Fraser

Chuck - I have been there and done that, with a whole stack of T shirts.

Most cars will probably reverse only a mile or two over their whole life, so wear on the flanks is very unusual - most of the wear comes from people crunching the gears. (note: this is NOT true of the 3 synch boxes where the reverse gear is also the straight cut 1st gear).

Wear on the leading edges of the reverse gear and the idler is VERY common and does not make the gear unserviceable.

The only problem is that if the teeth are well rounded then engagement of reverse gear can become difficult because the teeth won't slide past each other - to rectify this is a simple matter of using a small wheel on a dremel to restore the very slight point to the teeth - an inclusive angle of about 120 degrees is sufficient.

Chris at Octarine Services

I was told by someone who autotests midgets that he was surprised to find first/reverse half worn away when he rebuilt his box. They had given no problems and he was working on it for other reasons .
Or an optimist would say 1/2 remaining .
S Best

This thread was discussed between 04/09/2004 and 05/09/2004

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