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TC15/TC25 transfer case


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My RD822sx currently has a E9 with Mack 12 speed trans. I've been looking for a way to get a lower gear for heavy hauling. 

I've got a Spicer 1241c auxiliary but everybody I've talked to says it won't hold up in the RD with E9. I've been on the lookout for a Fuller AT1202 auxiliary, but they go from $3,500 for take-outs to $5,500 for rebuilt. Since all I need is a slower off-road speed, I'm wondering if I'd be just as well with a 2-speed transfer case. Seems you can pick up a TC15/TC25 transfer case pretty cheap. I'm wondering if it would be a ok idea to just install one of these transfer cases and just not use the front output? 

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You can probably make this work as long as you pay close attention to plumbing the correct air and oil lines.  You will also need to be careful with driveshaft angles, since the input and output shafts have a pretty large offset.

Also there were lots of different HI and LO ratios available on these units. 

for example TC15 LO-2.59 HI-1.00 and TC25 LO-2.59 HI-1.36

Good luck if you try this.

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Were it me, I would install what the factory options were, a Fuller AT1202 (2.036/1.00), air shift AT1202A (2.036/1.00), or Spicer 1241C (2.37/0.812), 1241CT (2.37/0.812 with Power Tower), or 1241DT (1.59/0.812 with Power Tower).

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As long as you use your 1241 for low speed work it will probably work but if you start wanting to run long distance it will grenade, I don't know which bearing it is but one of them fails, there is a shop in WA. that  mills out the hole for the race and they install a larger bearing and then they hold up longer but still fail at some point. they were never built for high input torque, you can look at their input chart and you will see this,  Kenworth would not warranty 1241 put into a new truck but will 1202, mostly depends on the operator, take care of it and it will work, drive like a animal and it will fail. 

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12 hours ago, david wild said:

As long as you use your 1241 for low speed work it will probably work but if you start wanting to run long distance it will grenade, I don't know which bearing it is but one of them fails, there is a shop in WA. that  mills out the hole for the race and they install a larger bearing and then they hold up longer but still fail at some point. they were never built for high input torque, you can look at their input chart and you will see this,  Kenworth would not warranty 1241 put into a new truck but will 1202, mostly depends on the operator, take care of it and it will work, drive like a animal and it will fail. 

The bearing you speak of, is probably the one that was down in the 1241 when I got it. It's a small needle roller bearing that connects the input shaft to the main shaft. It took out the input shaft with it (wore the bearing surface out). I've got it all fixed up with new bearings, main shaft, and rebuilt the air shift mechanism. It's currently for sale.

Another problem I've ran into is the RD822sx uses 1880 u-joints. They don't make a yoke that large for the 1241, so either I've got to have something made, or use one of those funky 2 sized joints.

I've found what is supposed to be a good take out 1202 for $3,500. I might bite the bullet on it. 

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  • 3 months later...

I am thinking the same path with the tc15. but I cant give any advice not that far yet. only thing I know is you have to delete the diff in the case or have "lock up" engaged all the time...ehhh?

btw have you ever put your hands on a TC15/25 do you happen to know the weight?

Edited by glenbjackson
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