Skyjacker High clearance Skid plate for TJ

[BlackSheep]

Greetings,
I'm wondering if anyone else has swapped out the stock skid plate on the TJ for a high clearance skid plate. I have put the skyjacker high clearance skid plate on, and I am having a bit of trouble with it.

I'm driving a '97 TJ with the 4.0L 32RH auto NP231 combo. I do have the fixed yoke/CV driveshaft and the raised motor mounts as recommended.

It is definately related to transmission/ t-case/driveline angle that is changed significantly with the high clear plate. When I put my stock plate back on, I don't experience the same situation.

What I'm hearing is a grinding/growling type noise during the slack between on and off throttle (and vice versa).

For example(and this is only one example), when you are going down a hill (like coming off of parleys into SLC), you're not always on the throttle, but you're not always off the throttle. You spend quite a bit of time with just a small amount of throttle (like trying to 'match' the engine speed to the wheel speed). This is when I hear the grinding/growling sound, and it lasts as long as I maintain this throttle setting.

Has anyone else had any experience with these high clearance skid plates on their TJs (or anything else for that matter)

thanks
jd

 

[I Lean]

Not a TJ (or anything similar) but I heard a similar noise from mine, when under no-load driving like that--turned out to be my rear driveshaft. (two different times, once was U-joints and once was the slip-spline)

 

[spencurai]

that sounds familiar. you might be over extending your slip yoke. check it by grabbing the center of the shaft and trying to wobble it back and forth for spline play. i have a worn slip spline and it couldn't make up its mind in those situations as to coast or drive, in the middle there is slop and slip can sound like grinding when it gets to gyrating. make sure you have it in neutral with no load on the shaft.

 

[BlackSheep]

Originally posted by spencurai
that sounds familiar. you might be over extending your slip yoke. check it by grabbing the center of the shaft and trying to wobble it back and forth for spline play. i have a worn slip spline and it couldn't make up its mind in those situations as to coast or drive, in the middle there is slop and slip can sound like grinding when it gets to gyrating. make sure you have it in neutral with no load on the shaft.

Guys,
thanks for the feedback. I was afraid that my driveshaft might now be too short. The transfer case is raised about 2", thus in theory it should require a longer driveshaft. I thought I could get away with it, but apparantly I can't. As a temporary fix, I'm going to install a transfer case lowering kit (I have to go to Moab this weekend!!!). I've spent too much money getting other things squared away lately.

Although my driveshaft is fairly new, I assume if I overextend it I would get the symptoms you are describing. Yes?

thanks
jd

 

[I Lean]

Originally posted by BlackSheep


Guys,
thanks for the feedback. I was afraid that my driveshaft might now be too short. The transfer case is raised about 2", thus in theory it should require a longer driveshaft. I thought I could get away with it, but apparantly I can't. As a temporary fix, I'm going to install a transfer case lowering kit (I have to go to Moab this weekend!!!). I've spent too much money getting other things squared away lately.

Although my driveshaft is fairly new, I assume if I overextend it I would get the symptoms you are describing. Yes?

thanks
jd

That makes sense to me. Since there's less spline engagement, there's probably more slop allowed.

Post back if/when your driveshaft is lengthened, I'd be interested to know if that alone solves your problem.

 

[BlackSheep]

OK,
I've done it. I put in a transfer case lowering kit. It lowered the t-case/skidplate by 1 3/8".

Before I lowered it, I measured the driveshaft length at 18 7/16". After the lowering kit, the driveshaft measured 18".

I have no more noise. As soon as I have a benjamin to spare, I'll take it over to six states and have them check the driveline.

I think that is my trouble. My driveline is too short.

thanks for the input, I'll post when I make mods to my driveshaft.

jd

 

[BlackSheep]

Just an update. Met Andy at 6 states today. We talked about lengthening my driveshaft, but he also cautioned me that I would have to put adjustable control arms to lesson the pinion angle before I could remove the T-case lowering kit.

Well, re-tubed driveshaft, new control arms.......sounds like a lot of money to put into my ride. I'm currently looking at picking up some upgraded axles (waggy D44), and I don't need to spend a couple benjamins to fix something that isn't really that much of a problem with the lowering kit, when I am working on replacing the existing axles. I'll probably need a new driveline after replacing the axles anyway!!

jd