4 speed gear damage

[jrusso07]

Finally pulled the engine on the 66. Tore into the transmission today. It has severe cluster gear/countershaft damage due to countershaft bearing failure.

Some pics for your enjoyment. I have another 4 speed that I will rebuild and use the best parts from the two transmissions (without interchanging gears of course)

[Habitat.pat]

Well that sucks! Good luck with your spare.

Peace,
Pat

[Bwk2000]

Damn
That looks like you were minutes away from having a catastrophic, case destroying failure of epic proportions. The type they write about in verse and tell the tale by song down through generations - Well, pretty bad at least …

[jrusso07]

The car was just delivered, and it drove off the trailer and around the neighborhood fine (low speeds). I went to put it into the barn and the transmission would make a loud bang in any gear but 4th (straight through). So, i drove it in 4th and finally pulled it out to see what the issue was...

I knew it was toast before I removed it so I started looking for a replacement. I was able to source a used one locally from a friend for a barter. He and I do the brakes on his 67.5 and I get the transmission. Good deal both ways!

[jrusso07]

The transmission is all apart. Some interesting and troubling finds…

1. No needle bearings at all on the rearward side of the counter shaft. See pic of countershaft wear

2. Main shaft nut was finger tight

[23yrRebuild]

Check the case and thrust washers for excessive wear....that's where the trouble can start for the 4-speed countershaft....especially if the tranny has been idle for a long while, and there isn't enough lubricant on the thrust washers when it's fired up, after sitting.....BTDT !
Mike

[jrusso07]

I checked out the case and thrust washers. Washers have some galling on the inside (gear side). Case looks ok. I was surprised to see the lack of needle bearings on the rearward side of the cluster gears. I still haven't torn into the replacement transmission yet. Maybe tomorrow if the temperatures drop a bit. It gets awful hot in my metal pole barn...

[keith0alan]

My recommendation as a routine maintenance item is to check the cluster gear shaft whenever you have the transmission out to change a clutch or whatever. Replace the shaft and needle bearings if there is any wear. Shafts and needles are way cheaper that the cluster gear, shaft and needles. The shaft is hard chrome plated. As soon as the chrome wears through is is done.

[jrusso07]

Makes a lot of sense to me, Keith!

[jhayden]

To pick up on Keith's recommendation, Dann (Rallye) recommends the following when the transmission oil is changed if the car is still together:

"... take off the transmission oil pan and grab the end of the countergear that has the small gear on it. Grab it and try to wiggle it up and down or back and forth without turning it. Does it move? A little movement of a bearing in that direction is A LOT." p.160, Datsun Roadster Parts Catalog

Jon

[redroadster]

Don't think there hard chromed I put together new parts
It s 4130 case hardened + silica+,Bronx ,but like gun barrel that chrome look from the cherry red heat
4130-40 rusts very quick

[keith0alan]

It may not be hard chrome but there is certainly a hard surface that will wear through. The material underneath looks way different.

[jrusso07]

Today I tore down the replacement transmission. The forks and rods are worn and the needle bearing for 2nd was toast. So, I will go through the synchros to get the best surfaces on the bands and then assemble the replacement transmission gears with the good forks and rods. I have new needle bearings for the counter shaft and main shaft gears along with new roller bearings for input and main shafts.

Dose anyone recommend molykote grease on internal parts like sleeves and needle bearings during assembly? I could just paint everything with 90W oil as I assemble it.

[notoptoy]

May not be kosher to the experts, but I used Engine assembly lube/White lithium when re-assembling. Have had no issues since.

[redroadster]

Any auto grease is a no no because it stays put at high temp and will hold debrie , vasiline works , trans assy lube