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Transfer Case Drop?

M

motormayhem

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Hey guys,
I tried to post this in the tech section, but it looks like I don't have the correct privileges to do that. Anyway I have a 1984 M1009 with 4" lift, 36"mtr's, and 3/4 axles. Ever since I installed the new axles, a 14 bolt and D44 with 4.10's (over the stock 3.08's), I have had a vibration at 55 that makes the entire truck shake. If I get above 57-60 it is gone and if I drop below 55 it is gone. My question is what would cause this to develop after the swap. The u-joints are good and greased. I have a lengthened driveshaft in the rear as the stock one blew the transfer case the first weekend I owned it since it was too short. My question is can I get by with the stock mounted center crossmember since I have a longer driveshaft (measured to the correct length) or is that causing my shaking and damaging the bushing in the slip yoke of the np208? I am afraid to lower the tranfercase as I am worried I would have issues with a longer driveshaft now :dunno:. If the transfer case isn't getting harmed im fine with living with the shaking as I normally don't drive right at 55.

Thanks Guys,
Miles
 
folkenheath said:
Assuming all your u-joints are in good shape and your d-shaft is balanced properly, , tires are balanced etc, your pinion angle is probably off.

Check these out...

http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

http://www.4xshaft.com/driveline101.html

But there are numerous things that could cause this. You also should be more specific. Is the steering wheel shaking? Is it coming from the back of the vehicle, etc...
Click to expand...

The shaking is throughout the vehicle. Feels like your driving on a washboard road where the humps are pretty close together.
 
check for locked front hubs? if its that violent, maybe try pulling the front shaft. That'll at least help narrow down the possibilities
 
I'm going through the same problem also. I have pretty much the same set up as you. We have been talking about it the last couple of days. Not sure how to post a link to the thread. Look for "back on the road again (with a problem)".
 
My hubs are defiantly free. I'm thinking it may be due to the fact that i just noticed that one of my rear shocks is heavily damaged and about to fall off. Back to the original question, how many people are using a dropped t-case for 4" lift? Is it recommended or would a longer drive-shaft suffice?
 
dropping the case is not really a good idea. how are your rubber mounts? ubolts tight? take some pics of your rear driveshaft angles.
 
obijuan said:
dropping the case is not really a good idea. how are your rubber mounts? ubolts tight? take some pics of your rear driveshaft angles.
Click to expand...

The rubbers are kinda old. The ubolts are nice and tight. I cant get a pic as I am out of town for the next 3 months. If it is any help it is a stock np208 tranfercase at stock height going to a 14 bolt FF axle with 4" block lift. The 14 bolt is pointed slightly up.
 
You want the pinion 1 - 2 degrees below parallel with the t-case output with the standard driveshaft.
 
I just dropped my case the other day and now it rides perfect. No vibes. It might not be the best way to do it but, it will do for now.
 
I wouldnt drop more than 1". After that, there may still be some pinion angle issues to deal with, I still have a hint of vibe at a certain range, but its not near as bad as before.

I will be adjusting my pinion angle later, after I install a "proper" lift kit.

This may be of some help:

http://www.youtube.com/watch?v=dNIaoNGJoYc


Your description of "riding on a washboard road" is accurate to what symptoms I was having.

GL,
Andrew
 
Last edited by a moderator:
I think the steering was a good job. But i would suggest parking the truck till you change the blocks on the front axle to springs. Not only is that setup dangerous but it is also aginst the law to use blocks on front axles.
 
Shhhh... I have springs on my 'To Do' list, right at the top... as soon as I can get work. But thanks for the follow up, and I agree, blox need to go!
 
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