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Spicer 1452A 5 Spee Main Spec Request / Spicer 1241C Question
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By 84KWhopper - Thursday, December 30, 2021 4:29 AM
Hello all, I have done quite a bit of reading across the forum in regards to the Spicer 5+4 transmission set up, specifically the 1452A / 1241C combination.

Lots of good information, but I wanted to hopefully get more detailed information regarding both units.

Specifically, does anyone have the dimensions / weight / oil capacity or service information for the 1452A main transmission or a PDF to share? I have not been able to find anything official online.

Same would go for the 1241C if handy, but not as critical.

I recently purchased a 1984 Kenworth C500 dump truck with a BC3, 5+4 and 5.38 Rockwell Meritor SSHD axles. Topped out the truck will do about 55 or 60mph if you really push it, but it will crawl up a tree of course.

I would like to put a 3406B and a conventional 13 / 18 speed into it at some point for better road speed. Keeping the 1241C auxiliary would be nice if it meant I didnt have to re-do the entire driveline, but I am worried about it holding up to the Cat and different main. The current Cummins is only rated for 300hp I believe.

Thank you to anyone who has information regarding the transmission or suggestions on how to best repower the truck for better road speed / everyday use in 2022.

I am also considering gutting the aux, swapping the rear ends down to a 4.11-4.30 range and just making a new driveline if that proves easier and less problematic.
By Geoff Weeks - Thursday, December 30, 2021 7:58 AM
Depends on what trans you are going to use. Gear up and then back down at the rear is never a good thing, before large driveshafts and high torque engines it was the only way.
If your going to re-power a modern trans makes sense, find parts for an odd-ball obsolete trans, while broke down under a load is no fun.
There used to be a guy on here out in Colorado that ran a modern Spicer 6X4 set up with a twin counter-shaft main and aux. He loved it, but was a lot of work and finding parts was difficult.
I ran a 3406B with an RT0 14615 and found 4:11's good on 20" rubber< actualy mine were two spd rear 4.11 and IIRC 5.63 in low. More gears then needed but always one for the job!
If I had more money then sense I would have selected a non-OD trans and rears to make the best use of it.
Gearing up and than back down puts a lot of energy into heat in the boxes that could be used to move the vehicle.