Thought on U-joints and Tandems

[spicergear]

Many people have done the single lockout and double spline axleshaft in the middle rear (front tandem) on the trucks leaving the rear-rear as the drive. The big 1500 series U-joints go from the T-case to the front tandem, then the jackshaft between the two uses 1410's. When the front tandem is 'unlocked' that would mean the 1410 jackshaft is pushing all 14,000 lbs of truck. Throw a little load on and you're pushin 10 ton pretty quickly.

Anyone look at this? I know the 1410 torque load is up there...but I haven't calc'ed that kind of weight.

Just sort of a passing thought as my tandems skipped along now and then on a road trip over the weekend-

 

[jwaller]

the trans was the weak link in my truck. it gave up long before anything else did. I posted pics of it in a topic on here somewhere.

 

[Stretch44875]

I vary what axle is driving in the rear for tire wear. An if I'm hauling heavy, I run both axles, even if it's all on road time.

 

[Jake0147]

To apply torque to the joint, it needs opposing forces. The transmission turns the shaft, and the pinion resists being turned. The rear (inter-axle) driveshaft is designed to support the maximum forseeable forces from one axle. The main driveshaft (transfer case to first rear axle) has to be designed to resist the maximum forseeable forces from two axles. Freeing up one means that you've reduced the maximum possible torque that the main driveshaft could ever see. Without a power divider, the rear driveshaft always operates under enough torque to cause a minimum of two NDTs to slide down the pavement...
IMHO, "not as strong" doesn't necessarily mean "weak" or "overloaded" or "not fully up to the job". I can't see any issues coming of it. Like jwaller said, barring neglect and/or parts that have exceeded their service life, something else is probably going to give out first anyway.

 

[cornrichard]

The big issue is that the weight of the driven wheels is shared by the tandem wheels. I removed my rear drive shaft for a 500 mile trip this summer. I did not have a load on the way out and just a lube trailer on the way back. When I would hit a large bump, and believe me there were plenty on the interstate this summer, I would spin tire as the front tandem left the ground. This was a severe shock load on the tranny. I know the original question was about locking hubs, but I think the main failure would be the transmission from the shock of an overreving motor slamming into very solid rear end and u-joint system. My truck made the trip but the very first thing I did when I got home was replace the rear drive shaft. It will not be coming back out.

 

[jwaller]

The big issue is that the weight of the driven wheels is shared by the tandem wheels. I removed my rear drive shaft for a 500 mile trip this summer. I did not have a load on the way out and just a lube trailer on the way back. When I would hit a large bump, and believe me there were plenty on the interstate this summer, I would spin tire as the front tandem left the ground. This was a severe shock load on the tranny.

this is exactly what blew up my tranny. now I step on the clutch every time I see a bump coming.

also be aware that the way the suspension is designed it wants to pick up the front axle making that one the WOSRT one to drive on. you want the rear most axle pushing the truck.

 

[gringeltaube]

.......................

also be aware that the way the suspension is designed it wants to pick up the front axle making that one the WOSRT one to drive on. you want the rear most axle pushing the truck.

 

[spicergear]

Yep, and that's exactly why I made up a specific thread about it because it should be the rear axle pushing the whole truck-

 

[Coldfusion21]

And that is what happens when you unlock the hub on the front rear tandem right? What if you took out the axle shafts for a long highway trip, would that be of any advantage?

 

[cranetruck]

And that is what happens when you unlock the hub on the front rear tandem right? What if you took out the axle shafts for a long highway trip, would that be of any advantage?

There is no interaxle differential, so the axles will "fight" each other at all times on hard pavement. They will want to go straight, resisting any turning and any difference in tire rolling diameter will cause tire wear.

I remove the drive shaft between the two rear axles for my road trips (including the cross country one) and have had no problems other than excessive wear on the driving tires. It does reduce front tire "scrubbing" and also reduces the turning circle...better fuel mileage too....