Quadratrac rebuild questions - JeepForum.com
 
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post #1 of 4 Old 10-21-2021, 06:36 PM Thread Starter
Rexmortale
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Hey everyone I’m sure this has been beat to death already but I’m having trouble finding what I’m looking for. I have a 76 (or 77 been a minute since I looked at the title) cj7 with the amc 304, th400 with the quadratrac. This is a frame off restoration that I’m building as a retirement gift for my old man. I’m rebuilding as much as I can so he has no issues when he gets it. With the quadratrac, I haven’t split the case yet I plan on doing so in the near future, what is required to convert it back from a part time kit? I believe it has a part time but I’m unsure which brand. It looks to have factory jeep locking hubs and there are two stickers on the switch. The front one says part time which fell off and the one behind it says full time. When I split the case what indicators should I look for to tell if it’s part time or full time? I found another forum that showed a mile marker version but I know in the past there were other companies that offered a similar modification. If I can I would like to have a properly operating quadratrac, I know it’s not the best system but my dad said he had a Cherokee back when he was young that had it and it worked quite well. Also from what I’ve read most of the issues were simply due to poor maintenance. This is not going to be a rock crawler. It’s a restoration with “tasteful” mods. I know he’s not going to do anything crazy with it. Something nice and reliable that he’ll enjoy driving around town and occasionally on some dirt trials. Thank you for all your help.

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Last edited by Rexmortale; 10-21-2021 at 07:43 PM. Reason: Adding pictures
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post #2 of 4 Old 10-24-2021, 09:38 AM
jeepdaddy2000
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So the first step in assessing if you have a PT (part time) kit is to drive the Jeep with the t case and hubs disengaged. It shouldn't move or should act like the clutch (if it had one) is slipping.

Or, you can start the engine, unlock the t case (it is vacuum operated) and hubs, and try to rotate the front driveshaft. If the kit is installed and the vacuum motor in the t case is working, you will be able to rotate the driveline by hand.

If it has a kit and you decide to replace it, you will have to find a used LS (limited slip) unit to replace PT unit. The issue with this is the stock unit is a cone style LS and you don't know what you are getting. Personally, I would retain the PT kit because it doesn't require any special fluid and won't wear out like the stock LS. You will also have to check the PT kit to insure it isn't an OD unit, which takes a different chain. I don't remember the tooth count differences but you can look that up.

IMHO, your two biggest issues with the case is the chain stretching and/or the vacuum motor going bad. The chain stretching is a fault with the unit and is a common complaint. Replacements are available US made and I would get a spare. The vacuum motors are unatobium and if you can find a serviceable one I would toss that in with the spare chain.

You can swap chains and install/uninstall the PT kit with the t case still in the rig.

Paperwork will ruin any military force.
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post #3 of 4 Old 10-24-2021, 07:14 PM Thread Starter
Rexmortale
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Quote:
Originally Posted by jeepdaddy2000 View Post
So the first step in assessing if you have a PT (part time) kit is to drive the Jeep with the t case and hubs disengaged. It shouldn't move or should act like the clutch (if it had one) is slipping.

Or, you can start the engine, unlock the t case (it is vacuum operated) and hubs, and try to rotate the front driveshaft. If the kit is installed and the vacuum motor in the t case is working, you will be able to rotate the driveline by hand.

If it has a kit and you decide to replace it, you will have to find a used LS (limited slip) unit to replace PT unit. The issue with this is the stock unit is a cone style LS and you don't know what you are getting. Personally, I would retain the PT kit because it doesn't require any special fluid and won't wear out like the stock LS. You will also have to check the PT kit to insure it isn't an OD unit, which takes a different chain. I don't remember the tooth count differences but you can look that up.

IMHO, your two biggest issues with the case is the chain stretching and/or the vacuum motor going bad. The chain stretching is a fault with the unit and is a common complaint. Replacements are available US made and I would get a spare. The vacuum motors are unatobium and if you can find a serviceable one I would toss that in with the spare chain.

You can swap chains and install/uninstall the PT kit with the t case still in the rig.
Thanks. I did I little more research and if it is part time I’ll probably retain it. As for testing it the jeep pretty much came to me in pieces haha. Thanks for your help. As for as if it has an od unit was that a permanent od or was that something it would automatically engage? I’ve seen part for od but still unsure how they worked.
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post #4 of 4 Old 10-24-2021, 08:42 PM
jeepdaddy2000
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In order to get the "OD", they (Mile Marker) replaced the stock driven "sprocket" with a smaller one. This effectively gave a taller gear ratio between the drive and driven gears. This change in tooth count necessitated a shorter chain.

Paperwork will ruin any military force.
Chesty Puller
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