NEWS PARTS JEEP & 4x4 ATV & UTV

CJ7 w/TH400

2223 Views 5 Replies 3 Participants Last post by **DONOTDELETE**, Feb 8, 2000

1236

Discussion Starter · Feb 8, 2000

A buddy of mine recently picked up a 79 CJ7 with a swapped in TH400, likely from a FS Cherokee. The front drive shaft is pretty long, and has alot of slop in the slip joint. I read where Jeepsters with TH400 had a carrier bearing on the front shaft, presumably to provide stability due to the length of the shaft. Anybody familiar with this swap into a 7? Does it need a carrier bearing, or just get the front shaft reworked/replaced? Any other relevant info on this combo?
TIA

Lynn
'71/'48/'97

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CJDave

· #2 · Feb 8, 2000

/wwwthreads_images/icons/crazy.gif Just checking with my moonguy/wwwthreads_images/icons/wink.gif crew chief I found out that our '79 CJ7 with the TH400 does not have a midships bearing on the front driveline, and what is more, it doesn't need it. The driveline is so close to the tranny, however, that it had to be small diameter heavy wall tubing to make more clearance./wwwthreads_images/icons/wink.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.

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WILL

· #3 · Feb 8, 2000

i have a th400 in my cj7 as well (from the factory). the front driveshaft is indeed very long and my rear one has a running length of 17 1/2". there is no need for a carrier bearing for the front shaft, just get the splines replaced and keep grease in the slip joint.

79/CJ-7/AMC360/TH400/Q-TRAC/d30/d44/33's/RS9000s/Herculiner

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1236

Discussion Starter · #4 · Feb 8, 2000

Thanks for the quick responses, guys. I haven't crawled under this beast yet, but he has said the front shaft is a small diameter. The odd thing about his set up is that since it came from a FS, it has a model 20 xcase going to the centered rear diff. Definitely not a stock combo.
How much lift are you guys running? Any idea of the depth difference between the QT and the 20? Will, thanks for that rear shaft length measurement, gives him something to compare to. Just wondering these things, thinking moderate future lift, and vibe potential if rear shaft is extremely short.

Lynn
'71/'48/'97

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WILL

· #5 · Feb 8, 2000

i'm running a 4" lift with the quadratrac and an almost centered dana 44 rear out of a '70 wagoneer. the rear driveshaft only drops a couple of inches but there is at least a six inch offset. to correct for that, i took out the one inch spacer between the transfer case adapter and mount. then i dropped the skidplate two inches. i have a very slight vibration from about 2600 rpm to 2900 rpm. a double cv driveshaft would probably eliminate that but it's not much to worry about. with a dana 20, i don't know where the output will be front to back but it is definately higher. a single cv jointed driveshaft with the rear axle turned up shouldn't have any vibration.

79/CJ-7/AMC360/TH400/Q-TRAC/d30/d44/33's/RS9000s/Herculiner

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· #6 · Feb 8, 2000

Lynn:
The previous owner may have had the th400 as factory option and just ditched the chain driven q-trac. Thats what I did. I run a th400 to Dana20 to a centered diff AMC20. I run 4" lift without any driveline vibrations. I think the Dana 20 was slightly shorter than the q-trac. If I recaall correctly this meant I lengthen the rear shaft 1 1/2" and maybe the same for the front. Seems like the front yoke is set further back on the D20 than it would be with the q-trac. Before your start changing driveshaft lengths I determine what lift he wants to run first. I did my drive shafts when I was running a 2 " lift and should have waited until I put the 4" on. The front shaft on the th400 is a long, small shaft to be sure. Unfortunatley, it has to be in order to clear the trans. pan. A bigger shaft just wont work b/c of the proximately of the front yoke to the tranny. A few people have had to notch their pans to help with clearance problems. If you want me to, I'll be happy to take some measurements from yoke to yoke on the front and rear of mine.
Shain

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