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The input shaft for my tranny has a bit of an in and out play. What could be causing that?
 

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Dear Hieu T93:

The input shaft, AKA the primary motion shaft, has three things that control position. #1 is the tip bushing in the center of the crankshaft. This does not control thrust. #2 the primary motion shaft bearing, which is the front case bearing. This does control thrust. #3 the needle bearing between the primary motion shaft and the main shaft. This does not control thrust, but can be damaged by operation with a worn primary motion shaft bearing.

The bearing on the primary motion shaft is a ball bearing and the outer race should have a snap ring that is held captive between the bell housing and the front cover (throw out bearing guide).
If you have removed the front cover, there will be excessive thrust because the bearing will not be held captive. If the transmission is operated for an extended period with a bad front bearing, the gear on the shaft will walk away from the cluster gear, damaging both and possibly causing tooth breakage. The cluster gear is also known as the counter shaft.

The transmission should have a magnetic drain plug. Remove the plug and drain the oil. Look for metal on the magnet. Minute particles will build up but large particles are evidence of gear failure. You can also look at the oil you drained to see if has metallic swirls in the liquid, which is another sign of a larger problem. When the engine is running and the transmission is in neutral, the primary motion shaft and the cluster gear are rotating. You can listen with a mechanics stethoscope for unusual noise, although if you are not experienced in this observation, you will not know what unusual is.

Finally, if you need to replace the primary motion shaft bearing, you will have to have a special bearing puller or you will have to disassemble the transmission. If you have never worked on a manual transmission, it is not a do-it-yourself type operation. There are a large number of observations that have to made in order to determine the condition of a large number of parts. Most mechanics are incapable of a proper overhaul. You will need a specialist who has experience with standard transmission work. I have rebuilt dozens of manual transmissions and it is a difficult operation. If you do it wrong, you will have to start over again and may need to buy a lot more parts.

A used transmission may be your best option. Don't forget to check the drain plug. Don't forget to refill with oil after draining. Don't buy a transmission that has water in it. A proper overhaul will cost more than $1500.00. A used transmission is usually about $300.00.
 
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