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Unread 12-03-2001, 08:05 PM   #1
Bob Minge
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Join Date: Dec 2001
Location: Fergus Falls, MN USA
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4WD vacumn switch

Just bought a '75 J10 pickup. He said the vacumn switch on the dash took it in and out of 4WD. When I got home, tried it on snow and it didn't seem to make a difference. Front wheels always spun. Any help, advice or place to go to get more info???

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Unread 12-12-2001, 11:10 AM   #2
Hump
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Bob, you shouldn't have a vacuum switch on the dash. If you do, someone put it there. For that year J-10 that you have you should either have the Borg-Warner Quadratrac full-time four wheel drive, or the Dana 20 part-time four wheel drive. Only the late model FSJ's had the New Process transfer cases (NP229, NP231,...) that used the vacuum switch.

You probably have the Quadratrac, and that means that you are in four wheel drive all the time. You should probably check and make sure that your drivetrain is stock, or the guy you bought it from might not be being honest with you.

Check out http://www.ifsja.org/ i'm a member there. It follows the same format as here, but it is just for Full Size Jeeps. There are guys there with infinite knowledge about the big Jeeps, and there is never any flaming. The only dumb questions are the ones not asked.
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'90 MJ SWB 4.0L/auto/2wd (4wd conversion in the process)
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Unread 12-12-2001, 03:39 PM   #3
mud4me
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I know for a fact my 1977 J-10 had Quadratrac and it had a vacuum switch in the glove box. Same with my dads older Wagoneer (76 maybe?). Just curious HUMP, is that different than what you're talking about?

As for why your front wheel are spinning, I don't know. Does that mean only the front wheels are driving the truck?

I owned 2 J-10s, 1 Cherokee, and 1 Wagoneer, and never heard of that problem. I have a wild, unexperienced guess that maybe something in the transfer case is broken??

By the way J-10 is neat vehicle! Maybe one day I will restore one.
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Unread 12-17-2001, 11:48 PM   #4
Hump
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You're right mud, quadratrac's do have a switch or a button in the glove box for the e-drive. That switch puts the transfer case into part-time four wheel drive from full time four wheel drive. That means that you don't want to drive it anywhere where you don't have slippage, because everything is locked in. That switch it totally different from the dash mounted switch used for New Process transfer cases that take the Jeep from two wheel drive to part time four wheel drive.

As for the front wheels turning all the time, that is just a sign that it has full time 4x4. In other words, it is in four wheel drive all the time. That is how it is supposed to be...all the time. If his transfer case was broken, then he wouldn't be able to go any where. Your transfer case comes off the back of your tranny. The rear driveshaft come of the back of the transfer case, and the front ds out of the front. So if it is broken then nothing turns out of it.
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'70 J4800 Buick 350/T18/D20/D44/D60
'90 MJ SWB 4.0L/auto/2wd (4wd conversion in the process)
'98 & '01 XJ Classics both with 3" Skyjacker & BFG AT KOs
Parting '99 & '00 XJ Sports
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Unread 12-18-2001, 01:34 PM   #5
J4GRAND
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The QT uses a limited slip-type transfer case to divide the power between f & r. When one set of axles lose traction the QT supplies power to the axle not slipping. As for the vac (or e-drive) switch in the glove box. This allows the driver to lock the f & r together supplying power evenly to the two. It is to be used on slick surfaces only- snow, ice, dirt, mud, etc. An optional low range was also available and can be seen with a lever under the drivers seat on the trans hump or a handle labled low range under the dash.
Patrick V.
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Unread 12-18-2001, 11:21 PM   #6
Bob Minge
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Thanks for all the help everyone. Now for the next question. It has a single barrel carb and if there is a little hill or a head wind of 10MPH or more I am at 50 MPH. Top speed down hill with a tail wind was 65MPH. Oh, it has the 258??ci in line 6 cyl. Would going to a 2 barrel carb help hold the speed up to 55 or 60 with a wind or over small hills?? I am not looking for top speed but some sort of staying power at road speed. Thanks in advance. Bob
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