auto 4wd requires a CV front drive shaft. Also the vibration could be coming from rear drive shaft, make sure the U joints are phased correctly
What turns?
- Thread starter 99TanHoe
- Start date
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992door
Full Access Member
^ what he said.
when swapping gears to a lower ration a vibration that you typically might have only seen at 90, will now show up at a much slower speed. Been there
Right now with the new rear drive shaft installed and the front drive shaft removed, there is no vibration. I'm going to have the same shop that built the rear shaft check my front shaft for balance, if its OK then I'll have them build a new front shaft, if they think that it will cure the vib problem.
I was mainly wondering what was turning the front shaft while in 2wd, the front diff or the transfer case?
I wanted to make sure the front shaft was supposed to turn when in 2wd, because if its not supposed to then I might have another issue. If it is supposed to turn in 2wd and I could find out whats turning it, then I would know which direction to look if the vibration persists after the front shaft balance/replacement.
---------- Post added at 06:14 PM ---------- Previous post was at 06:12 PM ----------
That makes sense, what did you do about the vibration you encountered?
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992door
Full Access Member
It is not that the drive shaft is bad. It is getting in a bind because of the angle it is at. You can get one from rough country for 425.
Thanks, I'll check out the Rough Country one and compare it to what the shop will charge to make one. The rear shaft they built is heavy duty and really well made. By going to them directly and cutting the Off-Road shop middle man out of the picture I might get a pretty decent price. The rear shaft cost $550, but I'm sure the Off-Road shop added a little something on to the price for themselves.
992door
Full Access Member
If i am not mistaken you can get them to cut off the end by the transfer case and put the right one on and balance it.
I added a rear CV shaft, then had to shim the rear a bit, still gets some vibration but minimal. 2 doors get it bad when lifted due to steeper angles in the drivelines
I have a bad habit of over-thinking things most of the time. The answer was really right in front of my eyes the whole time. I had actually already seen the shaft on the Rough Country site but had forgotten about it.
Thanks Cameron, for pointing me back in the right direction. The Rough Country site strongly recommends the Dual Cardan Shaft for the Autotrac transfer case that my Hoe has. They don't have a picture but I did find another site with a photo if anyone else is curious.
http://performancelifts.com/cgi-bin/cart/GMDRVSHAFT.html
It's pretty much just a smaller version of what I now have in the rear. Their price is right in there with the Rough Country one.
I still want to get a bid from the shop that did my rear shaft. I'm just kind of "Old School" that way. I regularly buy off the internet but I like to deal with a real person, face to face when I can.
Thanks Cameron, for pointing me back in the right direction. The Rough Country site strongly recommends the Dual Cardan Shaft for the Autotrac transfer case that my Hoe has. They don't have a picture but I did find another site with a photo if anyone else is curious.
http://performancelifts.com/cgi-bin/cart/GMDRVSHAFT.html
It's pretty much just a smaller version of what I now have in the rear. Their price is right in there with the Rough Country one.
I still want to get a bid from the shop that did my rear shaft. I'm just kind of "Old School" that way. I regularly buy off the internet but I like to deal with a real person, face to face when I can.
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I'm reviving this thread to tie up all the loose ends. First Thank You, to all that commented and offered suggestions. I think every post had some accuracy to it with at least a couple that were "spot on" in reference to my problem.
The same shop that built my rear shaft (USA Driveline) modifed my front shaft. They cut off the transfer case end and installed a dual cardan CV similar to the one on my rear shaft. Just installed it yesterday afternoon and test drove the heck out of it.
There is ZERO vibration now, I took it up to 85mph and held it there for a while just to see if higher speeds would adversely affect it but it was OK.
I got a away about $60 cheaper by having USA Driveline modify my existing shaft over buying the one Rough Country sells. I'm sure the RC one is good but I felt alot more comfortable dealing face to face on this kind of deal.
---------- Post added at 12:02 PM ---------- Previous post was at 10:36 AM ----------
Now, for part two of my thread revival. By talking with local mechanics and doing alot of googling, I was able to verify many of the comments that were made about "What Turns" my front drive shaft.
To sum it all up for anyone new to this thread that may need to know, the following is how an AutoTrac system works:
2WD - the transfer case turns the front driveshaft but the front driveshaft is not turning the front Diff because the front diff is not engaged to the front driveshaft until one of the three 4WD modes is selected. I don't remember which, but one of the front axles is alway engaged to the front diff even in 2wd but the front diff is still not engaged to the front driveshaft until a 4WD mode is selected.
According to one of the local mechanics I talked to, when any of the 4WD modes are selected, there is a fork in the front diff that engages the other front axle. Once the other front axle is engaged, the ring and pinion is engaged with both axles and the front driveshaft is also engaged to the front diff.
4WD Auto - As in 2WD the transfer case turns the front driveshaft and clutches in the transfer case apply as much bite to the front driveshaft as necessary to compensate for slippage from the rear diff. I think it was the owners manual that stated: Fuel economy would be lower in 4WD Auto I am assuming due to the front diff being locked up in that mode and the possiblily of some amount of 4WD being applied at any given time from the transfer case clutches. I would think that this mode was developed for driving in snow/ice conditions so that some level of fuel economy could be maintained but 4WD was still available if needed.
4HI - As with most 4WD systems the transfer case is turning the front driveshaft at a 1:1 ratio and the front diff is locked up and pulling.
4LO - Same as 4HI but with a 2.72 transfer case gear ratio applied.
I am by no means an expert on this subject but I do like to know as much as I can about the equipment that I own. If anyone see's anything that I have blatantly misstated or if you have something constructive to add please feel free to comment.
The same shop that built my rear shaft (USA Driveline) modifed my front shaft. They cut off the transfer case end and installed a dual cardan CV similar to the one on my rear shaft. Just installed it yesterday afternoon and test drove the heck out of it.
There is ZERO vibration now, I took it up to 85mph and held it there for a while just to see if higher speeds would adversely affect it but it was OK.
I got a away about $60 cheaper by having USA Driveline modify my existing shaft over buying the one Rough Country sells. I'm sure the RC one is good but I felt alot more comfortable dealing face to face on this kind of deal.
---------- Post added at 12:02 PM ---------- Previous post was at 10:36 AM ----------
Now, for part two of my thread revival. By talking with local mechanics and doing alot of googling, I was able to verify many of the comments that were made about "What Turns" my front drive shaft.
To sum it all up for anyone new to this thread that may need to know, the following is how an AutoTrac system works:
2WD - the transfer case turns the front driveshaft but the front driveshaft is not turning the front Diff because the front diff is not engaged to the front driveshaft until one of the three 4WD modes is selected. I don't remember which, but one of the front axles is alway engaged to the front diff even in 2wd but the front diff is still not engaged to the front driveshaft until a 4WD mode is selected.
According to one of the local mechanics I talked to, when any of the 4WD modes are selected, there is a fork in the front diff that engages the other front axle. Once the other front axle is engaged, the ring and pinion is engaged with both axles and the front driveshaft is also engaged to the front diff.
4WD Auto - As in 2WD the transfer case turns the front driveshaft and clutches in the transfer case apply as much bite to the front driveshaft as necessary to compensate for slippage from the rear diff. I think it was the owners manual that stated: Fuel economy would be lower in 4WD Auto I am assuming due to the front diff being locked up in that mode and the possiblily of some amount of 4WD being applied at any given time from the transfer case clutches. I would think that this mode was developed for driving in snow/ice conditions so that some level of fuel economy could be maintained but 4WD was still available if needed.
4HI - As with most 4WD systems the transfer case is turning the front driveshaft at a 1:1 ratio and the front diff is locked up and pulling.
4LO - Same as 4HI but with a 2.72 transfer case gear ratio applied.
I am by no means an expert on this subject but I do like to know as much as I can about the equipment that I own. If anyone see's anything that I have blatantly misstated or if you have something constructive to add please feel free to comment.
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