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ant_8u 01-06-2013 06:08 AM

Is My Gearbox Worn? - Pictures Included
I've taken my gearbox apart for rebuilding, and need to check things out before rebuilding it

Since this is the first gearbox I've rebuilt, and I have no idea what I'm looking for I'm hoping someone can tell me what I should look out for?

ie: What are and aren't acceptable levels of wear, etc....

Now, on with the pictures.......

This is the end of the mainshaft, it looks as those the hardening has worn through to me (but I don't know what I'm talking about so I could be wrong)

Here you can see a small chip out of the first gear

This pictures shows some wear on the teeth, I've pointed out the worst one, but you might be able to see the others have wear too

Another chip, this one is on the reverse/selector hub

Another picture of first gear

And some general/overall pictures

So, what does everyone think?
Do I need a new first gear and selector hubs?
Is my mainshaft scrap?
I was planning on replacing the baulk rings and circlip on third gear, but I've heard the new ones are awful
What should I do about the input shaft?

Any other thoughts?

big gear head 01-06-2013 06:58 AM

The main shaft is worn where it runs in the bearing. There are places here where you can send the shaft and have it welded and re-ground. You may have some place like that where you are. Check inside the input gear to see if it is also worn. Chances are that if the shaft is worn the inside of the input gear will be worn too.

ant_8u 01-06-2013 11:52 AM


The input shaft looks ok from what I can tell

It runs on caged needle bearings if that makes any difference

Is there any type of hardening that could/should be done to the mainshaft tip, or is it just a case of grinding and renewing?

big gear head 01-06-2013 12:07 PM

It needs to be welded with a hard surfacing rod and then ground to the correct size. T5 transmissions are very popular here in the USA and they have a bad reputation for doing the same thing. There are several places here that recondition the shaft for the T5 and other transmission. Check with transmission shops around you and see if they know of anyone who can do this kind of work on your shaft.

ant_8u 01-06-2013 12:15 PM

Excellent, thanks!

Just to confirm (as I'm still very much learning)
I need to ask if they can "weld the mainshaft tip with a hard surfacing rod, and then regrind to original sizing"

Also, the tip is 12mm in diameter
Later gearboxes had an 18mm tip, but still have the same wear issues

Could I do something here to resize mine to 18mm, or would that make no/little difference?

Thanks again for your help

big gear head 01-06-2013 12:49 PM

If you increase the size of the shaft would the larger bearing fit inside the input gear? Your shaft could be welded up to the larger diameter and ground, but would you have to replace the input gear to make it work? The more heat that is put into the shaft from welding, the greater the chance of ruining the shaft.

There are several ways to seld the shaft. TIG welding is comon, but spray welding is getting more popular for shaft build up.

mmerlinn 01-06-2013 09:02 PM

Mainshaft needs to be fixed or replaced.

Check the bore of your input. If it looks the same, you will need to replace it.

Blocker rings need replaced.

Polish the sharp edges of the nick on 1st. As little as you use it, you won't notice any noise and the chip is not bad enough to worry about.

The 1st/2nd/Reverse slider should be replaced, but if you are careful shifting into reverse it could last a long time the way it is.

The 3rd/4th syncro is not bad enough to worry about.

ant_8u 01-07-2013 06:49 AM

Thanks again guys, it's all very much appreciated!

Some more pictures for you......

First picture shows Layshaft cluster

Here, you can make out the contact patch on the first gear
There is also a chip on the gear I have highlighted, and also the gear two steps nearer to the camera

Wear patch on second gear

Chips on second gear

Couple of chips on third gear

Front of layshaft
There's a small line where the needle rollers locate, but it doesn't seem to be worn into the surface

Rear of layshaft

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