Lateral Movement in Transmission Input Shaft

Greg Jones

Greg Jones

Well-known member
Rebuilding a stock transmission, and have everything back together. I notice slight lateral movement on the transmission input shaft. This is the big shaft with the nose that sticks into the pilot bearing. How much lateral movement is normal?
 
Slight movement on the input shaft is normal. Can't give you a quantitative answer, but I had minor movement with a new bearing pressed on the shaft. BTW - I used "shielded" bearings and pulled the inner shields off to facilitate improved lubrication to the bearings. Might consider a shift rod seal unit while you have the trans off. It will keep the rods from pumping oil into the clutch housing. It is installed in the clutch housing and is held in place by the two top housing-to-trans bolts. One other thought is to consider a conventional Zerk fitting on the U-Joint housing to simplify pumping much gease to fill the housing until it comes out the speedo cable connection.
 
The input shaft is riding on a large ball bearing which will naturally tend to allow for a bit of axial play. If it didn't, the bearing would be too tight for the application. Once the transmission is bolted up and the nose of the input shaft is home in the flywheel pilot bearing, that axial play, i.e., lateral movement, will be close to zero. Don't worry about it.
 
Thank you ursus. I searched the forum for the answer to this very question. The lateral movement I'm getting is about .100 to .110, does that sound about right? I hope so because I'm ready to put the engine back in and I don't really want to pull the transmission to put in unneeded parts.
Thanks again.
 
After rereading my answer I thing I misinterpreted your reference to "lateral movement".
There are two possible movements: 1) axial (back and forth, i.e., in and out) movement along the axis of the input shaft and 2) radial (rotational or up and down) movement as measured at the pilot bearing end. My answer related to radial movement although a very slight amount of axial movement my be found in the assembly. I've never measured this so am not sure if your .100 to .110 of movement is out of spec.

Maybe you could fashion a shim to snug things up?
 
It takes only a very minor amount of play in the bearing to give a significant movement way out at the end of the input shaft. If you have replaced the bearing as part of your rebuild, I'd run it. The pilot bearing will hold it all straight once it is installed in the car. Enjoy your slick, quiet transmission!
 
Like they said. The pilot bearing is the other half of the equation. My AA 4 speed had a load of slop there initially, but only a small amount after rebuilding. Make sure to replace pilot bearing and check fit of it on shaft.
 
Thank you all for your response. I'm definetly talking about the radial movement. I get zero movement in the axial direction which makes me believe that the bearing is ok and the pilot bearing will allow it to run true. Thank you all again.
 
Have you read the ongoing discussion about trans bearings being NO GOOD. Ck BEFORE you install your ******. FWIW
Paul in CT
 
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