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Discussion Starter #1 (Edited)
I already tried searching and got nowhere.

I have a D18 behind an SM420. Yes, it's in a Cruiser, but I figure there's more D18 knowledge here than in the LC forum. Both were professionally rebuilt and have about 100 miles on them. Everything seemed to be working fine.

The Cruiser has been sitting for a few months while I did some work on the body, moved the rear axle back (spring flip) and had the rear driveshaft lengthened. Now I hear a knocking noise from the transfer case when I decelerate. It's pretty loud. I can hear it when I put in the clutch and coast. It's also there if I put the trans in neutral while coasting. Also when I put the transfer case in neutral while coasting. It's definitely soemhow connected with the rear driveshaft spinning.

I have checked the driveshaft for clearance issues, it's fine. I have checked the transfer case shifter engagement and it seems ok. And yes, I checked to make sure there was gear oil in it :p

I am hoping it's a common problem with a simple solution. Anybody got any ideas?

Thanks in advance,
Phil
 

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I just can't think of anything that could cause a knock inside the D18 other than maybe broken teeth. Pull the inspection cover and make sure the trans gear has big torque. You might check the output yoke also. Remember that a knock is the predessor to KFB (Ker friggin boom). The D18 is really fairly simple. Are you sure it's not something else? The endplay on the output shaft should only be .004
 

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Discussion Starter #3
Thanks for the reply. I'm going to pull the rear driveshaft and check the output. Then I'll probably spin the transfer case without any driveshafts to see if the sound is still there. That should tell me if it's the D18 or not.

Phil
 

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you mentioned the 18 case has been rebuilt, but you haven't told us if you've addressed the biggest problem with that model of case: notoriously failure-prone intermediate shaft:
Novak Adaptor said:
The stock Model 18 intermediate or "idler" shafts seem to be good for about 30k miles before requiring replacement due to wear, pitting or other ails. The current aftermarket shafts available elsewhere are of an even weaker, softer grade of metal.

What's more, aftermarket tapered bearing-style shafts have less bearing area and less shear resistance, adjust and seal poorly and are unneccessarily expensive
Here's the Novak Adaptor site. There's also a link to a Jeep magazine article that further details it. the page offers and affordable fix. But it doesn't sound like this may be your exact problem

Good luck -
 

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Discussion Starter #5
Yes, the intermediate shaft has been replaced. I don't know for certain if it's a Novak shaft. The rebuild(s) was done by Marlin Crawler and he was very familiar with the D18. It's very similar to the early LC transfer case.

Thanks,
Phil
 

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It sounds like it might be the output shaft end play.It should be as close to min.spec. as you can get it .It is set by adding or removing shim at the rear retainer.
 
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