Broken Getrag Main Shaft Mystery
Thread Starter
Registered User
Joined: Mar 2014
Posts: 1,296
Likes: 308
From: PA near Harrisburg
Broken Getrag Main Shaft Mystery
A few of you have been following my work on my truck and you will be familiar with the story but not the conclusion.
When I bought the truck I knew that there was a problem with the trans. Specifically: I could shift the transmission through all of the gears with the engine running and without depressing the clutch and the truck didn't move or make any odd noises. I shifted the transfer case through all of the gears with no change. There were a number of theories about the situation posited by the good folks here.
When my cousin and I pulled the Getrag to replace it with an NV4500 I solved part of the mystery. The output end of the mainshaft had broken between the rear bearing and the transfer case. Upon further examination it appeared that the shaft had somehow broken, been welded back together, and broken again. I thought this because someone had used a disc grinder on the broken part of the shaft. I made the assumption that the PO had done this in the hopes that it would hold together long enough to sell to someone and pass the buck so to speak. I was still curious how the PO had managed to break the mainshaft. I've never seen that before. I figure he would have twisted off a drive shaft or broken the input shaft.
Today I spoke with the mechanic that used to work on the truck for the PO. I showed him the chunk of broken output shaft and he told me what he thought had happened. At one point he had replaced the countershaft, input shaft, and bearings. The rear bearing on the mainshaft had apparently overheated and the race had fused itself to the shaft ( the PO had frequently towed a large 5th wheel camper, probably in OD). The mechanic had used a torch and chisel to get the remains of the bearing off the shaft then a disc grinder to clean it up. Apparently the heat from the bearing failure and subsequent removal took the temper out of the steel and weakened it to the point of failure (probably trying to tow the 36' camper trailer).
Here are some pics.
When I bought the truck I knew that there was a problem with the trans. Specifically: I could shift the transmission through all of the gears with the engine running and without depressing the clutch and the truck didn't move or make any odd noises. I shifted the transfer case through all of the gears with no change. There were a number of theories about the situation posited by the good folks here.
When my cousin and I pulled the Getrag to replace it with an NV4500 I solved part of the mystery. The output end of the mainshaft had broken between the rear bearing and the transfer case. Upon further examination it appeared that the shaft had somehow broken, been welded back together, and broken again. I thought this because someone had used a disc grinder on the broken part of the shaft. I made the assumption that the PO had done this in the hopes that it would hold together long enough to sell to someone and pass the buck so to speak. I was still curious how the PO had managed to break the mainshaft. I've never seen that before. I figure he would have twisted off a drive shaft or broken the input shaft.
Today I spoke with the mechanic that used to work on the truck for the PO. I showed him the chunk of broken output shaft and he told me what he thought had happened. At one point he had replaced the countershaft, input shaft, and bearings. The rear bearing on the mainshaft had apparently overheated and the race had fused itself to the shaft ( the PO had frequently towed a large 5th wheel camper, probably in OD). The mechanic had used a torch and chisel to get the remains of the bearing off the shaft then a disc grinder to clean it up. Apparently the heat from the bearing failure and subsequent removal took the temper out of the steel and weakened it to the point of failure (probably trying to tow the 36' camper trailer).
Here are some pics.
Thread
Thread Starter
Forum
Replies
Last Post