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Trans assemby?

Old 08-13-03, 08:12 AM
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Trans assemby?

Had an NA tranny die on me a couple months back. It was a year old rebuild built by a local shop. It was an S5 or 89-92 trans. Was silky smooth but decided to eat fourth gear or more correctly the 1:1 drive and counter gears. I decided to disassemble it and do my own rebuild figuring it can't be too hard. First thing I noticed was that fourth gear only meshed about half the gear surface. The gears were very poorly aligned and the wear pattern showed it had been that way since the start. No wonder it broke I thought. Matter of fact none of the gears aligned properly. The most obvious fault was the bearings on the output shaft and the back of the counter shaft. The output bearing was setting half way outside the case and the counter bearing was half inside the case. At first I was mad because this was obviously not right. But upon further inspection of three more similar Mazda trannys (one 1st and 2nd gen trans and one from a Courier pickup which is visually identical for practical purposes) it was confirmed that all four, two of which were factory built all had this characteristic. I'm about to start building a new box and have ordered all the shims offered but from my measurements it doesn't appear I'll be able to make everything line up with the shims offered by Mazda. What gives?

Chris
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Old 08-13-03, 08:58 PM
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I'm about to start building a new box and have ordered all the shims offered but from my measurements it doesn't appear I'll be able to make everything line up with the shims offered by Mazda. What gives?
How do you mean they will not line up? Do they not offer shims small enought? because you should be able to just stack them up to the right amount. I have never worked on any of the mazda gearboxes (with the exeption of Formula Mazda cars) but the ones I have worked on work that way!..

Btw your math could be wrong. I was off the first few times I tried doing it. What type of feeler gauges are you using?
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Old 08-14-03, 04:35 PM
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You don't need a feeler gauge or mic to see what I'm talking about. The difference is in 1/8th of an inch. I'll take some pics soon to illustrate.

Basically it comes down to the fact that the counter shaft is not long enough and I believe the bearing land and grooves for the snap rings that retain the output shaft bearing aren't where they should be. I've managed to shim the gear sets so that they mesh very well. Better than the four boxes I've looked at. But that still leaves the fact that the rear bearings will not set in the case properly. As I said, the output shaft bearing rides half way outside the case and the rear counter bearing rides half inside the case. The bearings are only about 1/2" wide. So you end up with only around 1/4" holding the load. Terrible design.
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Old 08-22-03, 01:43 PM
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Here's a pics of what I'm talking about. The lands for the bearings on each shaft should align with each other and the outer land of the case. They don't. I have a machine shop working on some shims that will get me where I need to be but those shims are not offered by Mazda. What I want to know is what everyone else (Speedsource, ISC, KD, etc.) is doing.




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