GMC 4104 Drive shaft installation

[Bob & Tracey]

Hi,

We lost our drive shaft due to the propeller shaft flange nut coming off. This differential was set-up and installed last Oct. and has about 1500 mi. since. The guy who did the set-up claims this happened because the drive shaft was installed backwards. Which way should the drive shaft be installed?

By the way this failure caused major damage to our toad, including; bumper cover damage, undercarriage replacement, control arm replacement, steering gear replacement, exhaust system replacement, floor pan replacement due to 6" hole... I do feel the car prevented serious problems for the heavy traffic around us. We were traveling at 60mph when the shaft exited.

Thanks,
Bob

[Utahclaimjumper]

 That nut torques to 6 hundred foot pounds and is safetied with a cotter key,,,somebody screwed up,, they don't just fall off .>>>Dan

[Bob & Tracey]

Dan,

Agreed they don't just fall off. The manual says 800 to 1100 foot pounds and this one was a locking nut, no cotter pin. The guy I bought this differential from "set it up" and replaced the pinion seal. I feel the nut was never tightened correctly.

[Utahclaimjumper]

 Even if it had been a paltry 200 pounds with a lock nut it would not have loosened. It smacks of a "home garage" job >>>Dan

[Bob & Tracey]

The guy who did this work is well known and has a good reputation.

Anybody have an opinion on the orientation of the drive shaft? 8V71 with V730.

[TomC]

Typically the spline side of the drive shaft is on the transmission side. And to make sure the splines are lined up correctly, the U-joints should be positioned the same on either end. Good Luck, TomC

[Bob & Tracey]

Thank you Tom,

[luvrbus]

All the GM buses I have been around have arrows to align the shaft on a original drive shaft,the slip joint is always on the transmission end 

[Bob & Tracey]

Another question,

The threads on the pinion shaft are stripped, we are considering two options to fix this. One is to machine new threads a size smaller and the other is to build up missing metal by welding and machine new threads to the original size. My concern with the second option is, will the heat produced by welding effect the pinion shaft in a negative way.

Thoughts appreciated,

[luvrbus]

They spray the metal on to stay away from the heat I wouldn't weld on the pinion shaft myself

[eagle19952]

Another question,

The threads on the pinion shaft are stripped, we are considering two options to fix this. One is to machine new threads a size smaller and the other is to build up missing metal by welding and machine new threads to the original size. My concern with the second option is, will the heat produced by welding effect the pinion shaft in a negative way.

Thoughts appreciated,

i would source a new one... are you disassembling this differential ?

[Bob & Tracey]

Eagle,

No, we do not plan to remove the differential, the pinion cage has been removed and the shaft/gear removed from the cage. We feel it would be a mistake to replace the pinion shaft/gear without changing the ring gear.

[luvrbus]

Eagle,

No, we do not plan to remove the differential, the pinion cage has been removed and the shaft/gear removed from the cage. We feel it would be a mistake to replace the pinion shaft/gear without changing the ring gear.

Agreed a big mistake take it to automotive machine shop most can spray the metal.I would pull the differential,how is he going to set the back lash without pulling the complete assembly   

[Bob & Tracey]

The backlash is set by shims between the differential housing and the pinion cage? If we reassemble everything the way it was it should be ok? We are at Eagle Nest in Nashville.

[luvrbus]

The backlash is set by shims between the differential housing and the pinion cage? If we reassemble everything the way it was it should be ok? We are at Eagle Nest in Nashville.

That's your call