Which sees more stress, Tcase or doubler

[disciplerocks]

I know most people run a 1350 as their doubler because they had a 1354 stock. I had planned on installing a 1354 planetary set into a 1350 housing, but I wanted to do this on the unit that sees more stress. So which is it, the doubler or the transfer case?

 

[CHKNFKR]

t-case. think about it. your doubler does the same thing a tranny and a t-case do, its a torque multiplier. the input load to the doubler will be the same as the input would be to the t-case if you have no doubler (or when the doubler is in high) using the doubler, you are multiplying the input load to the t-case behind it.

This is the reason people who use doublers use the maincase first and only shift the doubler into low as needed. same with running multiple transmissions.

 

[disciplerocks]

I'm sure I could have figured it out, my brain just didn't want to focus on it. Kinda sucks cause I wasn't wanting to open up my t-case, but thanks for the info.

 

[Hahnsb2]

The T-case sees more stress. The axles shafts see the most, as they're under the most gear reduction, the tranny input shaft sees the least. Everything after a gear reduction sees more stress than before the gear reduction, if that makes sense.

Lets say you have a 200ft/lb motor, with a 1st gear of 3.40:1, you now have 680 ft/lbs out of the tranny and into the first t-case. The t-case is 2.48:1, you now have 1686 ft/lbs coming out of the first case entering the second case, remember the first case only saw 680 ft/lbs from the tranny. Now out of the second case you have 4182 ft/lbs traveling out the driveshafts to the axles, if the axles have 4.56 gears, you're sending over 19,000 ft/lbs through your axle shafts.

 

[gribly]

And wheel hop will artificially double and triple that number because of drivetrain inertia.

 

[4x4junkie]

It should be noted however, tire slippage typically will prevent the torque from ever winding up to anywhere near 19,000+ ft-lbs in your axle shafts. An exception might be if you get a tire jammed up in between rocks or something.
But yes, if you have a 4-planet and a 6-planet gearset on hand, best would be to put the 6 in the rear case.

One thing you never should do though is run the doubler in low with the t-case in high (this puts extreme stress on the intermediate coupling shaft between the two cases which can break it).

 

[CHKNFKR]

Lets say you have a 200ft/lb motor, with a 1st gear of 3.40:1, you now have 680 ft/lbs out of the tranny and into the first t-case. The t-case is 2.48:1, you now have 1686 ft/lbs coming out of the first case entering the second case, remember the first case only saw 680 ft/lbs from the tranny. Now out of the second case you have 4182 ft/lbs traveling out the driveshafts to the axles, if the axles have 4.56 gears, you're sending over 19,000 ft/lbs through your axle shafts.

Minus the energy converted to heat you are absolutely correct!