Theres a weird vibration in my transfer case?

[ih8mud]

I have the big-o np203 transfer case and when i get goin around 50mph the shift shakes and makes noises.  But when i let off the gas it stops completely.  Anyone have an idea of what this could be?  Please reply!

[76GreenBeast]

It could be the shifter is worn and its trying to scoot into a different range (maybe N or Hloc).  The torque/power going through it when you drive may be enogh to cause it to try to come out of High and into Hloc (which is definitely not good on a dry road).  Is the shifter tight or does it have some slop in it?

[ih8mud]

The shifter feels tight.  Could it be the chain, it has about 130,000 miles on it?

[76GreenBeast]

I hope not, that's a major job if you don't have the tools/facilities to do it.  While you're in there you might as well put a part-time conversion kit to save you some gas mileage (my '76 gets about 8 mpg, 13 on the interstate with the full-time 4WD, along with a quart of oil).

What kind of noises are you hearing (grinding, whirring, etc)?  When was the last time the T-case fluid was changed?  You could try changing it (I think it takes 10W-40) and seeing if there's any metal in the oil.....Do you know if this truck was run hard off-road, that could wear out the T-case pre-maturely....

[ih8mud]

Yeah, changing the fluid has been on my list of many things but ill try that soon.  I've heard to use 10w 30, but seeing it is older i might as well us 10w40.  I hear that with a part time you should run it in 4 wheel drive for a little ways to get the oil plashed around.  My front hub bearing are already worn down from the full time, i think i might just keep an eye out for the np205.  Thanks for the help.

[bflobil]

You might want to grab the slip yoke on the front drive shaft and see how much wear there is(wiggle it perpendicular to the drive shaft).  If you remove the drive shaft and then drive it the vibration may go away.  Generally with the part time transfer case it doesn't wear on one side of the slip yoke because it is always turning but with those kind of miles it may be worn enough to create an "out of balance".

[ih8mud]

Yeah i can see how that could be causing it.  I'll get under it tomorrow and mess around.  Ill post back, thanks though.

[ih8mud]

I got under it and checked out the front slip yoke and its fine, but the rear has alot of slack in it.  I got my grease gun and greased both fittings.  But would the rear slip yoke probably be it, if not im still replacing it because that good to be riding around with.  Oh yea when i greased the front the grease came out where the male and the femal fittings are, but on the rear it came out the front?????

[k5lady]

My 74k5 w/6'' lift has the same problem.  I have read that we're not the only ones.  I have yet to find a solution.  I have replaced the engine, transmission, rear end, all bearings, drive shaft(rear) and rebuilt the t-case.  Nothing made any difference.  I was told to lower the t-case, and the angle was to great.  How would that be done without lowering everything else?  I also have a major KLUNK at 5 to 10 mph.  I think the two noises are related.  This vibe has caused everything in the drivetrain to be rebuilt or replaced.  SNDow my million dollar blazer is worthless.  Help! any ideas would be greatly appreciated.

[Blazin]

You can put 3/4" to 1" spacers between the cross member and the frame to lower it a bit.

[Destro]

My guess is the rear driveshaft. My slip yoke is shot also and I have the same problem. Replace all your u-joints too. That bad slip joint has probably beaten them up a bit. At least on mine it did. A local driveshaft place quoted me $160 to put a new one on and rebalance,they gotta wait till the tax check gets here though!