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Old 12-24-2015, 07:05 PM   #1
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Default Need help identifying vintage CAT diff

Greetings,
I'm in the process of restoring an old Schumacher CAT XLS and I'm missing the whole rear end (diff, shocks wishbones etc). I found a diff case on eBay but I'm unsure as to which model the diff case belongs to.
I've attached some links to the pics
http://i1168.photobucket.com/albums/r491/grunger73/Mobile%20Uploads/image_zpse3pf4jqt.jpeg
http://i1168.photobucket.com/albums/r491/grunger73/Mobile%20Uploads/image_zpsgr9kctjn.jpeg
http://i1168.photobucket.com/albums/r491/grunger73/Mobile%20Uploads/image_zpspme2biub.jpeg
Any help is greatly appreciated
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Old 12-25-2015, 01:07 AM   #2
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It does look similar but I'm no expert on the older Schumacher cars. If you get no luck here it may be worth trying the vintage section on oOple.
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Old 12-25-2015, 02:43 AM   #3
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this may help,if you have not already seen it
and going over your pics looks like you were right on regarding model.
http://www.oople.com/rc/manuals/xls/
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Old 12-25-2015, 10:30 AM   #4
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Thanks for the info guys.
I bought it not knowing if it's the right one because these parts have become so hard to find. Figured I'd take a chance. The Cat swb, xl and XLS are so very similar that it's hard to tell if it's the correct one even after looking at the manual.
Merry Christmas
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Old 12-26-2015, 03:19 PM   #5
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That indeed looks to be an XLS transmission. The layshaft or topshaft is an MMS one piece hop-up part. The top deck looks XL, the chassis some sort of saddle pack aftermarket XLS. The bumper definitely is XLS.

Edit: ... and your lower front arms are on the wrong way around.
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Old 12-26-2015, 06:21 PM   #6
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XL/XLS w/Robinson spur.
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Old 12-26-2015, 07:08 PM   #7
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Thank you for the detailed explanations. I'll have to correct those arms. I'm a little bummed that it's a mix of xl/XLS parts but I guess I have to start somewhere. Was the MMS configuration a lot better than stock? In other words, should I bother trying to find the correct parts to change back to stock?Also, I would like to eventually add a slipper. If I keep the MMS setup, is there a specific slipper I should be looking for? From what I've read, the BossCat slipper is usually recommend.
Thanks again. You guys are a wealth of information.
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Old 12-27-2015, 03:52 AM   #8
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The XLS had the differential in the spur gear, and an integrator in the back. The idea was to be able to adjust the amount if drive going to the front wheels. Nobody ever wanted less than full drive though, and the sheer number of balls and thrust bearings made the system all gritty and unnecessarily complicated. The solid topshaft and rear drum diff made the transmission slightly more durable. I'd keep the hop-ups if I was going to drive the car.

Oh, and a slipper is nice but not a must. I drive my XLS/Procat without. 13.5 brushless and 2S lipos.
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Old 12-27-2015, 10:09 AM   #9
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Quote:
Originally Posted by Mattias View Post
The XLS had the differential in the spur gear, and an integrator in the back. The idea was to be able to adjust the amount if drive going to the front wheels. Nobody ever wanted less than full drive though, and the sheer number of balls and thrust bearings made the system all gritty and unnecessarily complicated. The solid topshaft and rear drum diff made the transmission slightly more durable. I'd keep the hop-ups if I was going to drive the car.

Oh, and a slipper is nice but not a must. I drive my XLS/Procat without. 13.5 brushless and 2S lipos.
Ok. Now that you've explained how it works it makes more sense to me. I really don't see why I would ever want less drive to the front either. Pretty cool though that that was implemented back then. A lot of engineering must have gone into these cars back then. Almost like having a centre diff. I have a Trinity 13.5 short stack that should work nicely. Has anyone run anything hotter using the mms setup without problem?
Edit: what was the difference between the mms and wasp rear diffs?
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