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View Full Version : Front driveshaft spins in 2wd with unlocked hubs


Desert4x4
August 26th, 2017, 11:34
So I installed the Yukon locking hub conversion. Now when I go over 65mph the front drive shaft spins causing unwanted vibration. I have verified that the drive shaft is spinning with undercar videos. It will do it even if I run the rear wheels in the air and vehicle stopped (front wheels stopped). Anyone know if this is normal ?

RCP Phx
August 26th, 2017, 12:43
What year and transfer case?

Desert4x4
August 26th, 2017, 12:46
What year and transfer case?

1999 NP242

Desert4x4
August 26th, 2017, 13:05
It's just annoying because I installed the $1200 kit so I wouldn't have anymore front driveline vibrations.

themauler
August 26th, 2017, 14:49
I bet one of the hubs is installed incorrectly or your jeep hates you :)


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Desert4x4
August 26th, 2017, 14:55
I bet one of the hubs is installed incorrectly or your jeep hates you :)


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I don't understand, if the front wheels are stopped how could one of the hubs cause it? I'm testing this when the rear wheels are jacked up and I run them to 65mph. I'm sure I could lock the hubs and then try the same test with the rear tires in the air and the driveshaft will NOT spin. I'm just trying to figure out why there is so much drag causing the front shaft to spin when in 2wd. Perhaps the center diff in the NP242 is not designed to alow the front shaft to be stopped.

TRCM
August 26th, 2017, 15:10
I'd bet it's simply enough in the t-case to cause it.

Just because it isn't being powered doesn't mean there isn't still enough friction for it to turn. Just like an open diff, if both tires are in the air, both will turn, even tho you can easily stop 1 side with your foot. And the 242 case I believe has a diff in it just like your axle to let you drive in 4wd all the time.

Can you stop it from turning with something easily ?? if you can, then if you lock your front hubs in, I'd bet the front shaft stops turning. (if you try this, be ready in case it comes off the jack stands - We don't know right now for sure what is wrong)


and I would NOT recommend running it up to 65 on jackstands...if it comes off in the least, you're gonna get very hurt
.

RCP Phx
August 26th, 2017, 15:12
You got to remember that the 242 is a "part-time" case.

Boostwerks.com
August 26th, 2017, 15:22
Does the front DS spin freely when not running?

I wouldn't be surprised that it would start spinning simply from the slight bearing drag of the TC.

Desert4x4
August 26th, 2017, 15:37
It does spin freely. It won't keep spinning if I spin it by hand though. Hmm. I just don't like having to keep it under 65 to keep the vibes from happening.

Desert4x4
August 26th, 2017, 15:38
I used tie wraps to hold the shaft but the shaft ripped them off when I revved the jeep up to 80.

Desert4x4
August 26th, 2017, 16:32
A few days ago I was hoping that I could just use different fluid to make the front driveshaft less prone to freewheeling. I switch from Mobil 1 ATF to Mobil 1 5W-30, and neither fixed the issue.

Boostwerks.com
August 26th, 2017, 16:37
sounds like your pinion angle must be extreme

Desert4x4
August 26th, 2017, 17:15
sounds like your pinion angle must be extreme

It is, but... I had angled it to perfectly straight, and the vibration was still there. The driveshaft was also rebuilt, balanced and trued, and the vibration was still there. I also replaced the transfer case, no change.

Desert4x4
August 26th, 2017, 17:16
You got to remember that the 242 is a "part-time" case.

Yes I know. But I'm not using 4x4 on the street.

trippled
August 26th, 2017, 20:51
Does the front DS spin freely when not running?

I wouldn't be surprised that it would start spinning simply from the slight bearing drag of the TC.

This. It happens.

Boostwerks.com
August 26th, 2017, 21:25
It is, but... I had angled it to perfectly straight, and the vibration was still there. The driveshaft was also rebuilt, balanced and trued, and the vibration was still there. I also replaced the transfer case, no change.

Do the vibes disappear with the DS removed?

TRCM
August 26th, 2017, 23:40
This. It happens.

Yep..it happened on my 79 Ramcharger with a NP203 t-case, even after the part time conversion kit was installed....it's just friction.

You could reach up and stop it with your hand, then let go, and in a minute or so it'd be spinning again.

Demonoid369
August 27th, 2017, 00:43
Sounds like the driveshaft needs better balancing possibly.
Just to clarify, you are driving in 2wd right?


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ehall
August 27th, 2017, 06:20
Make sure you can freely spin the front driveshaft by hand. After that I wouldn't worry about it. Probably surface tension from the oil film creating drag for the chain drive.

Desert4x4
August 27th, 2017, 08:53
Do the vibes disappear with the DS removed?

Yes. Very smooth without the front shaft.

Sounds like the driveshaft needs better balancing possibly.
Just to clarify, you are driving in 2wd right?


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Yes of course. I'm using 2wd not 4FT.

Make sure you can freely spin the front driveshaft by hand. After that I wouldn't worry about it. Probably surface tension from the oil film creating drag for the chain drive.

Yeah I can spin it by hand no problem
Hmm ok thanks.

Jim Malcolm
August 28th, 2017, 17:48
OEM staft? At 4" of lift with aftermarket LCAs and a 242 t-case in my 94, the measurement I gave when getting the new one was nearly 2" longer than the OEM spec. There's only 3" of travel... Smooth as butter at all speeds now after wasting money having the OEM one straightened, balanced and rebuilt.

Desert4x4
August 30th, 2017, 06:14
OEM staft? At 4" of lift with aftermarket LCAs and a 242 t-case in my 94, the measurement I gave when getting the new one was nearly 2" longer than the OEM spec. There's only 3" of travel... Smooth as butter at all speeds now after wasting money having the OEM one straightened, balanced and rebuilt.

I ordered a custom shaft. I don't remember the length. It's a long travel drive shaft.

Desert4x4
September 2nd, 2017, 15:02
I used two of the thick plastic tie wraps to hold the driveshaft from spinning. So far it as worked. I've had the Jeep up to 75mph which is about the max I like to do. Problem solved, I suppose.

TRCM
September 2nd, 2017, 15:12
If you have a new custom D/S in the front, and it still does it, you either have issues internal to the tcase @ the front output, or you have issues in the diff.


Either way, they need to get fixed.


Or you can do like I did for a long time in the truck in my avatar.....keep the front D/S inside the truck with all the tools to install it when needed. I did that for MPG, as it was a FT 4wd truck back then.

chris420
September 2nd, 2017, 21:58
I have the Warn lockouts and my driveshaft does not spin in 2WD. When the hubs are unlocked the front wheels spin on the bearing whithin the hubs. I have seen Dodge and Ford trucks with manual lock outs that have enough drag to spin the front DS very slowly but nothing fast enough to create driveline vibes. The best way to test is get underneath the jeep with all 4 tires on the ground with it in 2WD and grab the front drive shaft with 1 hand and spin it, it should spin freely if it does not then with your hubs are not working properly or your transfer case is stuck in part time or full time 4wd.

chris420
September 2nd, 2017, 22:02
On a second note I have a 6" lift and run stock front drive shafts with no issues. I also run stock front drive shafts in the rear with no issues. I have an NP242 TCase. You don't need a custom drive shaft stock shafts will do however you may need to change the flanges depending on your set up.

Desert4x4
September 7th, 2017, 12:26
I forgot to add that I have 5.13s in this XJ. So the driveshaft speed is significantly higher than with stock gearing.

TRCM
September 7th, 2017, 14:18
I forgot to add that I have 5.13s in this XJ. So the driveshaft speed is significantly higher than with stock gearing.

what size tires are you running ? may not be that much more

Desert4x4
September 7th, 2017, 17:49
what size tires are you running ? may not be that much more

35x12.5r15

Yeah, well its about 3,000 rpm at 65 mph

TRCM
September 8th, 2017, 14:57
Ok...according to the grimmreaper site, 35" tires, AW4 trans, NP231 tcase, you should be doing 81 mph @ 3000 rpm down the highway

IF you stay in 3rd gear, it should be 61 mph @ 3000 rpm


65 mph with those tires & gears should be 2400 rpm, not 3000............

Does you trans actually go into lockup & OD anymore ??

I know I had issues with mine in the past, and it didn't lockup or stay in OD, and even with 31's, I was spinning 2400 @ 65 mph