1960 T-10 rebuild - main shaft question

[Joe P.]

I have torn apart my transmission and ordered all the replacement parts. I recently noticed some pitting on my main shaft, that is assembled with needle bearings into the 4th gear (input). Larry at D&L was a great help, and hat to bug him again with this issue.

I looked at the needle bearing and they look no worse for wear. I will be putting in new needle bearings and appreciate any comments on the condition of the pitting on the main shaft in the pics.. Is this something that needs to be replaced or repaired or will it be ok to install as is?

Thanks. Joe

[Joe L.]

Re: 1960 T-10 rebuild - main shaft question

I have torn apart my transmission and ordered all the replacement parts. I recently noticed some pitting on my main shaft, that is assembled with needle bearings into the 4th gear (input). Larry at D&L was a great help, and hat to bug him again with this issue.

I looked at the needle bearing and they look no worse for wear. I will be putting in new needle bearings and appreciate any comments on the condition of the pitting on the main shaft in the pics.. Is this something that needs to be replaced or repaired or will it be ok to install as is?

Thanks. Joe

Joe------


If that's the only problem with the mainshaft (e.g. the gear teeth and especially the synchro teeth are OK), then I think it will be OK for re-use. However, I would want to confirm that the OD of the pilot shaft is within spec. It should measure right at 0.592".

[Joe P.]

Re: 1960 T-10 rebuild - main shaft question

Thanks Joe, i measured the diameter and got .763". its the diameter on the main shaft that fits into 4th gear and fits into the needle pins.

i apologize if i have the nomenclature incorrect, but it is the longest shaft at the bottom of the picture below..

[Joe L.]

Re: 1960 T-10 rebuild - main shaft question

Thanks Joe, i measured the diameter and got .763". its the diameter on the main shaft that fits into 4th gear and fits into the needle pins.

i apologize if i have the nomenclature incorrect, but it is the longest shaft at the bottom of the picture below..

Joe------


You had it described correctly; I interpreted it incorrectly. I thought you were referring to the input shaft but I don't know why since the picture you included was obviously not an input shaft. It is the pilot shaft on the main shaft that you are referring to. Please disregard the dimension I posted. I do not know the diametrical dimension of the pilot shaft on the mainshaft of a T-10. Larry Fischer should be able to tell you, though.

[Duke W.]

Re: 1960 T-10 rebuild - main shaft question

It could be typical bearing spalling, which is a form of fatigue failure due to the race being repeatedly loaded and unloaded by motion of the rollers, and there's no way to arrest it. But that interface is not that highly loaded, and there is only speed differential between the clutch gear and mainshaft in other than 4th gear.

Carefully measure the diameter in several places and feel for any roughness. Chucking it up on a lathe to polish the surface may also be a good idea.

I don't have that much experience rebuilding old transmissions, but there are guys out there that do. They might be able to tell you if this surface erosion is "typical" for an old trans and whether or not it will reduce future durability.

If you can find a new or used mainshaft at a reasonable price that doesn't exhibit this appearance, I suggest using it.

Also inspect the outer race of the mainshaft connection. It's on the inside/rear of the clutch gear shaft, and report whether or not you see similar surface erosion.

Good photos!

Duke

[E B.]

Re: 1960 T-10 rebuild - main shaft question

Joe, replace old pilot bearing as well. Ed

[Mike M.]

Re: 1960 T-10 rebuild - main shaft question

I wouldn't use that mainshaft. mike

[Domenic T.]

Re: 1960 T-10 rebuild - main shaft question

I had multiple failures on the T-10 mainshaft where yours is pitted. I actually had some metalized and ground back, but the metalizing was soft and the failure came back. This was in the early 60's. Maybe hard chrome would bring it back if you can't find a good shaft, otherwise I'm with Mike and wouldn't use it.
What Duke said would prolong the life because it is stationary when in 4th gear. Hard chroming was not popular back then, so it may be an option.

Dom

[Joe L.]

Re: 1960 T-10 rebuild - main shaft question

I had multiple failures on the T-10 mainshaft where yours is pitted. I actually had some metalized and ground back, but the metalizing was soft and the failure came back. This was in the early 60's. Maybe hard chrome would bring it back if you can't find a good shaft, otherwise I'm with Mike and wouldn't use it.
What Duke said would prolong the life because it is stationary when in 4th gear. Hard chroming was not popular back then, so it may be an option.

Dom

Dom-----


I think that hard chroming could definitely restore the shaft to better-than-new condition. However, I think the cost of it would likely exceed the cost of a new replacement shaft.

I really think that the shaft as-is would be fine if the car is a limited use type car (as almost all classic Corvette are). In limited use, I think it would outlast the owner. However, if one were going to use the car on extended and relatively frequent road trips, a new shaft might be best.

[Joe P.]

Re: 1960 T-10 rebuild - main shaft question

Thanks guys for your feedback.. i will give Larry a call and see if he has a replacement shaft or can make a recommendation. the rebuild is back on hold, along with the suspension and steering... these old cars are fun to work on.. but more fun to drive..

[Domenic T.]

Re: 1960 T-10 rebuild - main shaft question

Joe,
I think you are right. There was a shop in Banning that was reasonable, but think they are gone. As Duke pointed out the rollers are in use in all but 4th gear. Most of the T-10 I did were young guys that blasted around town in 2nd and 3rd gear so everyone could hear the beast under the hood.

Dom

[Timothy B.]

Re: 1960 T-10 rebuild - main shaft question

I think it's a good idea to get the opinion of someone that builds these transmissions. Chances are if there is damage to the pilot shaft there may be damage to the clutch gear race on the other side.

If so, you will definately get a rumble/vibration when driving. i had this exact problem on a Spicer transmission years ago on a Ford truck, only difference is the repair parts were available.

[Michael B.]

Re: 1960 T-10 rebuild - main shaft question

A reputable rebuilder would not reuse that shaft as is. It can be chromed and reused. There is a lot of side loading this shaft in 1st, 2nd, & 3rd gears. Slop in this bearing is going to cause the transmission to pop out of gear under load.

[Richard G.]

Re: 1960 T-10 rebuild - main shaft question

I really don't get the defects pattern. Typically spallilng starts with a small defect and then it spreads in the direction of rotation. This appears to be particle denting? In any case I would replace the shaft. I believe most the replacement are made in India and are of reasonable quality and not terrible expensive.
Check out this web site:

https://www.thegearbox.org/T10.html

T10 Mainshaft 27 spline or 16 spline
New T10 mainshaft, 16 or 27 spline.
From $154.70

[Jim D.]

Re: 1960 T-10 rebuild - main shaft question

I wouldn't reuse that main shaft. I'm surprised the output splines are straight though. The majority of T-10's I've rebuilt have had twisted splines, a known weak spot.