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post #1 of (permalink) Old 09-06-2001, 10:14 PM
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How could you test a quadra-trac?

I've looked a two jeeps recently, 1 79 CJ7 and 1 79 Cherokee both "Golden Eagles" ironically. Both had Quadra-Trac transmissions. If you were going to buy one how would you check to ensure that those autos were working as planned? Could you jackstand the vehicle in the air and turn on the gas? Could someone explain the quadra trac to me? Was it all time 4wd and then you trun the switch in the glove box and that makes it low 4wd? Thanks for the help.
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post #2 of (permalink) Old 09-06-2001, 10:41 PM
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Re: How could you test a quadra-trac?

It kind of depends on the condition of the transfer case whether lifting the tires off the ground will tell you anything. I have one quadratrac that has no limited slip left that you can turn one driveshaft without the other turning.

I also had one installed for a while that wouldn't lock and I didn't have a frone driveshaft on either. The limited slip was so tight that as long as I didn't floor the gas, I could drive it around without the front output spinning and the rear one staying still.

The transmission in those is just a plain TH400 with an AMC bellhousing pattern. The rear pattern is the standard six bolt TH400. Here is a little more on the transmission: http://www.off-road.com/jeep/tech/trans/th400.html

The transmission output turns a sprocket in the quadratrac transfer case which turns a chain which turns another sprocket. The offset sprocket has a differential in it similar to an axle limited slip differential. Picture the sprocket having the same role as the ring gear and the output shafts driven the same as the axle shafts.

Some quadratracs came without a low range too. The CJ-7 you looked at most likely had the low range with a little lever mounted to the transmission hump in front of the driver's seat. The cherokee might not have the low range but if it did, the lever would be barely sticking out from under the seat on the side of the transmission hump.

Both should have a vacuum switch located in the glove box with a green normal drive mode and a red emergency drive mode. All the emergency drive mode does is slide a collar (via vacuum lines to a shifter on the transfer case) to lock the rear output shaft to the sprocket to lock the differential. This is similar to the way the ox locker works only it uses a cable instead of vacuum.

You can use the jeeps in one of four modes: high range unlocked, high range locked, low range unlocked, and low range locked. The low range is 2.57:1. Here is a little more information on the transfer case: http://www.off-road.com/jeep/tech/xfer/qtrac.html

A lot of people don't like the quadratrac and it is a little misunderstood but in my opinion, it is not that bad a transfer case. I bought my CJ-7 with 90k miles on it and now have 188k miles on it. I have replaced the chain twice in that time but it is a simple job. The lower rear output is a plus for the driveline angle when lifting. The full-time feels a little more stable on the road compared to the times I removed the front driveshaft and locked the transfer case for rear wheel drive. Since I installed lockrights front and rear, I also installed front locking hubs so I can lock the transfer case and unlock the wheel hubs. I have tried driving with the hubs locked and the transfer case unlocked but the front locker just has way too much torque steer.

Last winter on the snow covered roads it did fine in full-time mode even with both the lockers. I think this was because the driveshafts could still turn independently.

Maybe I have been lucky with mine holding up to the abuse I give it but I have no complaints with using it.

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post #3 of (permalink) Old 09-06-2001, 11:28 PM
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Re: How could you test a quadra-trac?

[img]/wwwthreads_images/icons/smile.gif[/img] WILL has done a good job of telling you about QTs. That transfer case is SO MALIGNED by people who do NOT understand it. As manufactured, it isn't as good as it could be with the cone clutches inside the differential making it want to NOT act as an inter-axle differential, and because of that, and mismatched tires, the gas mileage suffers. My personal modification is to disable the cone clutches and have genuine OPEN center, and then when you want to YOLK EM UP for hard going, the lockup works A LOT BETTER with the cone clutches outa there. IN SNOW, they have NO PEER......except for the NV242 in the Cherokees which has open center OR lockup.[img]/wwwthreads_images/icons/crazy.gif[/img]

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