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Transmission "knock" noise diagnosis pics

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Old 01-20-10, 08:10 AM
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Transmission "knock" noise diagnosis pics

I had a problem with my 94 manual trans that several others reported.

A "knocking" bearing noise when the clutch pedal is released in neutral, reverse, first and second gears. The trans shifted perfectly, synchros and gears were ok.

I purchased a used transmission, and lo and behold it had the same "knocking" noise, although less severe, than my original!

I took my original trans to a locally owned, independent, transmission repair shop that has been around for many years. They guaranteed that after their diagnosis/repair there would not be a noise problem.

Bottom line:
There was one bad bearing on the mainshaft that was badly "pitted"/"spalled". It is a needle roller bearing, located at the end of the main shaft that holds the Rev/1/2 gears. There is a separate shaft and bearings that hold 3/4/5 gears (that's why the noise was only present in Rev/1/2 gears).

The attached pictures show this bearing. After repair, I've no problems. This bearing could be a common failure item on these transmissions.
Attached Thumbnails Transmission "knock" noise diagnosis pics-fd-failed-trans-bearing-1.jpg   Transmission "knock" noise diagnosis pics-fd-failed-trans-bearing-ii-.jpg  
Old 01-20-10, 08:34 AM
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needs more track time

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Yep. All of my bearings were shot in the original trans. The rebuilder suggested that the oil wasn't appropriate for the usage - perhaps too thin of an oil.
Old 01-20-10, 08:42 AM
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Donkey Puncher

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TX

Thanks for sharing. Great !! Just another thing to worry about!!! Gotta Love Fd's..
Old 01-20-10, 09:05 AM
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RAWR

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Originally Posted by 1TxRx7
Thanks for sharing. Great !! Just another thing to worry about!!! Gotta Love Fd's..
Gotta love a 15 to 17 year old sports car...

It's not the FD, it's any car of this age that has been driven hard its whole life.

Thanks for the post. Simple. Concise. To the point, and with pictures! Threads like this are what is needed on a forum so people can self-diagnose problems.
Old 01-20-10, 07:41 PM
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RX-7 Bad Ass

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How much did the repair run you? I'm wondering how far they had to tear into the transmission to get to and fix that one bearing.

I know some fixes like repairing a bad 5th gear synchro are actually pretty easy as you don't have to pull the entire transmission apart to do the job.

Dale
Old 01-21-10, 12:49 AM
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Roxann7

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Wow, those look like some really high quality photos!!!
Old 01-21-10, 04:22 AM
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Cost?
The local shop (Al's Trans and Gear) did the repairs for $300 including the part.

Removal?
The whole transmission had to be disassembled (the mainshaft must be removed). He guaranteed that the trans would be quiet, so I chose not to replace all the bearings (just the defective part).

Want to replace all bearings?
Malloy has a complete kit in stock for about $500.

Note:
the above is for bearing repairs only, gears and synchros, if needed are separate ($$).

Bearing spalling?
This failure is not totally understood (brief Google info search). Gear oil, age. load effects combine to cause the failure.

Use?
This car had 95,000 miles, I am the second owner. Never tracked, but was driven like a "sports car"................
Old 01-21-10, 05:42 PM
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edit: I believe the Malloy kit includes synchos as well..................
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