front drive shaft

Can anybody tell me if the front drive shaft that connects to Tcase turns freely when my 2K Blazer 4 door, V6 is not in gear and not moving?I do appreciate it.Thank you .

Can anybody tell me if the front drive shaft that connects to Tcase turns freely when my 2K Blazer 4 door, V6 is not in gear and not moving?I do appreciate it.Thank you .

No it does not. The front driveshaft is live at all times, just like the rear driveshaft.

Thanks for a quick response oldmaster. But, do I need to replace the u-joint that connects to front differential, cause it has play?

Yes, it needs to be replaced. It has power to it when you are moving and could/will cause a vibration, and put undue stress on the transfercase and front differential.

Thannnnnkk you Oldmaster! You guess what, I have a slight vibrations in steering wheel and floor and humming noise under driver's floor.You are a psychic. How did you know this? I will replace the u-joint as you had said so it won't stress the Tcase and differential. Will this solve my
issue?Appreciate it much, OldMaster.

Typically a universal joint will not cause a vibration in the steering wheel, unless the joint is extremely worn. It can however, cause the humming noise and vibration in the floor that you are referring to. By the way, I'm not psychic, just an old master, thanks for the kind words.

Okay OldMaster. I'll do replace the u-joint and probably balance it too at the shop.I'll keep you posted the result soon.Maybe this week.BTW, my blazer looks like yours, flaming red.Thank you again.

That front driveshaft rear CV joint requires you to use a block of wood and give it a few hits with a hammer in the removal direction to release the internal snap ring (like the front CV to diff joints) then it will slide off the transfer shaft. Have to drop the front u-joint first of course. Tell us how the balance worked cause I was going to do mine next week to see if that smoothed the vehicle vibration even more.

Everyone is right about how to change the U-Joints.

I usually agree with Old Master, however I know that my 4wd is working properly, and if I go crawling under my Blazer with it in park but not in 4wd the front drive shaft will spin freely. I've done this, so that's from first hand experience.

This not a full time unit that I'm talking about.

Mine's an 85, and shifter not pushbutton, but I'd be suprised if any are different in that aspect.

If the transfer case or hubs are locked it won't spin. (I've got a posi lok, cable kit so I can have the front axle locked with the Blazer shut off)

Before anyone calles me a B.S.er please take the 30 seconds to test your unit out. You'll see that I'm right.

OBP,

You're exactly right with part time 4WD. You can disengage the front driveshaft, and if it’s equipped with lock outs on the hubs, you can disengage the front axles and differential too. It's a much more versatile system with less wear and tear on transfer case, u joints, and front differential, and gas mileage is usually better as a result. However, the Blazer we're referring to here is a 2000 and it's equipped with full time 4WD. I'm not certain, but I believe GM went to that system with the second generation T series. Most of us 4X4 veterans know the difference, but someone reading this may not know the differences in the two systems.

OM

Thanks everyone for your great info. I'll go to a shop and keep you posted.I don't know the day yet but this week I hope. So mine is 2K and the front shaft does not turn(locked) if in park or idling or engine shut off. Okay, I know now.Great!

No it does not. The front driveshaft is live at all times, just like the rear driveshaft.

Is there a difference between the Autotrack (4 buttons) and the 2HI/4HI/4LO (3 buttons) model? Mine is a 2000 4WD with the 3 buttons and my front driveshaft does not turn when in gear, only in 4WD. In fact, my dealer has been trying to diagnose a vibration similar to a wheel bearing noise coming from the front end, but it disappears in 4WD. They wanted to rule out the transfer case spinning the front axle in 2HI so they tie wrapped the U joint to the torsion bar to verify it does not turn while in 2HI, and it doesn't.

Hello evryone that helped! I went to the shop yesterday and they checked the u-joint front shaft and it doesn't have a play(I was with them too).Only if you hold the shaft and turn it will have a 1/3 or 1/4 play either way. Also, the CV has play up,down,and sideways a little.They said it's normal to have a clearance but they mentioned about the gearbox inside the TC might have something to do with drivetrain vibrations. And the solenoid which they pointed out is that long tubular or cylindrical black (plastic?) on the rear right side of the T-case might need replacement. The mechanic drove the car(with me) for 2 miles and found nothing abnormal. Is this right? I mean I still feel a slight vibrations in the steering and dirvers side or the in the rear passenger floor(heard) and also in the hood. I have a 4 button switch(includes auto4W).

I still don't know what to do until now. The shop said it's normal to have a small play in the shaft,but the forum says it should have a zero play like the rear shaft.Mine has play on it when I put in park, engine off or in park and engine running. Can any one tell me like oldmaster or others? Thank you for your input guys.

I still don't know what to do until now. The shop said it's normal to have a small play in the shaft,but the forum says it should have a zero play like the rear shaft.Mine has play on it when I put in park, engine off or in park and engine running. Can any one tell me like oldmaster or others? Thank you for your input guys.

The output shaft of the transmission transfers power to the front driveshaft through a chain and gears. During use, the chain will stretch and is evident as rotational "play" in the front driveshaft. Under ideal conditions there should be negligible "play". The ring and pinion gears along with the bearings in the front differential also wear with use. To get a true idea of how much driveline "play" is coming from each component requires removing the driveshaft from the differential and checking both the transfercase output, and the differential input. Unfortunately those specifications, (to my knowledge) are only found in the GM service manual.

You seem to be left hanging on this one. Have a few of these, so:
The 4 button autotrac xfer case uses autotrak II syn fluid thats blue (dealer item about $7 a qt and it takes 2 qts). This case has known problems and GM says to get it hot, change the 2 qts with new, drive 100 miles, flush again and add 2 more qts. There are clutch packs in it that have friction problems especially if you drive alot in "Auto" 4Hi. I'd change it once and see if that helps before the 2nd change. That front shaft CV joint on the xfer case end has some play but the u-joint should not. Blazers have unequal length CV axles and this also creates some vibration. Make sure the front diff is full too with 80w-90.
Finally - if you look at the NP 243 and 246 xfer cases thay ARE both always active chain driven so the drive shaft always turns (does not pertain to the older manual xfers with manual hubs). The drivers side CV axle always is locked into the front diff and the passenger side has a coupler that is vac actuated.

Thank you for the comments. Alright, so I'll just go ahead and let them replace the u-joint in the front shaft.This way they will know if I need a rebalance.Or I might also need bearings for the T-case. Okay, i'll do that.

Muddog321 i appreciate your input.And as you have said i'll also put the autotrac II in my xcase and 80w-90 to the differential. Thank you a lot. Now i know that the cv joint to xcase will have a bit play but the u-joint to differential will not.Thank you .

Where is this xcase drain plug lacated at on my 2k blazer? Is it the one next to solenoid(black tubular or cylindrical) or by the rear of xcase. And i've heard there is another one plug for filling her up with autotrac II. I appreciate your help.I always like to read this forum but i can't find the answer and if there is a pic that would really help for any one here.Thank you again.