Gear Popping in 4 wheel drive

itllmakeit

itllmakeit

New Member
Joined
Aug 15, 2005
Location
Okinawa, Japan (camp foster)
Can anyone help?

Can not figure out what is causing my front end or xfer case to cause a very noticeable banging sound when it is in four wheel drive. It bangs like every other quarter turn. I had replaced the gears in the rear-end and after re-doing the math, I realized I put 3.72 gears in the rear vice 3.07 and thought that was the root of my problem. Does anyone have any ideas of what or where to begin tearing apart to fix???????? Thanks for any help.

It is a chevy 10 bolt front and 12 bolt rear by the way.
 
POPPING

If I read your post correctly you are now running a 3:72 in the rear and a 3:07 in the front. If this is the case, the front wheeels are slipped in a jerking motion to relieve the binding, caused by the different gear ratio. It goes like this, bind--hop--bind---hop, and usually only wheel has to do it, unless you are locked in both diffs. The real problem will be the situation where the tires cannot slip and something breaks.
 
As Larry said, it's a function of front to rear binding, which also occurs every time you make a turn. I'm not sure what make/model/year your vehicle is, but if the t-case has a chain, and if the chain and sprockets are worn enough, the chain will jump on the sprocket teeth when placed in enough of a bind. Some aluminum t-cases are especially prone to this, like the NP208 in my '88 Chevy did at about 140K and the Borg-Warner in the company Ford Ranger at 90K. I rebuilt the cases and all was well, but you'll need to fix the gear situation first or looking at the t-case will be useless.
 
Sounds like something broke w/ the mis-matched gears.....

Did you drive it @ all w/ the mis-matched set-up in 4wd?
 
I only drove it with the 3.72 gears for less than a foot because of the banging, I then removed the gears and replaced with the correct 3.07 gears.

The last time it was in 4 wheel drive I snapped the front drive shaft in uwharrie.

Since then I just drove in 2 wheel drive without front driveshaft till the rearend locked up.

Now that I am trying to fix it, she wants to make the banging sound. It will go less than a foot, feel as though the breaks are being applied and then "bang" and then start the cycle over. It only does it in 4 wheel drive.
 
To determine the cause of the problem, do the following:

1: in 2wd, pull out onto the street.
2: straighten up the wheels, and engage 4wd, lock the hubs.
3: Put it in gear
4: Drop the hammer.

Whatever comes flying off is the culprit.

Replace/upgrade parts until this no longer occurs. :D
 
I had the same noise in my Blazer--I thought it was in the axle or in the front drive shaft CV joint---it turned out to be the chain in the 203 T-case was stretched and when it was in 4-wheel drive the chain would jump teeth due to the front end being locked in---if this is the case on yours--I have a new chain I bought but never put in, if you want it I'll sell it to ya. There are, however, 2 different chains for those cases, a 2 1/2" and a 3", iirc. The one I have is the larger of the 2.

Just something else to check since the mix/matched gears could have caused the chain to stretch.

--Byron
 
Rich said:
To determine the cause of the problem, do the following:

1: in 2wd, pull out onto the street.
2: straighten up the wheels, and engage 4wd, lock the hubs.
3: Put it in gear
4: Drop the hammer.

Whatever comes flying off is the culprit.

Replace/upgrade parts until this no longer occurs. :D
Click to expand...

I tried it................

The banging is still there but not as bad as it was but it is now doing it also when I turn to the left but not to the right.

I reckon I will try to do something with the xfer case and see if it is the chain slipping.
 
To check the chain in mine--I took the bearing retainer off, the one that goes to the backside of the front D-shaft, and then with the front locked in, I had a friend of mine (make sure they aren't mad at you:D ) move the truck back and forth in the garage/driveway, while I was on a creeper under the truck holding on the frame so I would move with the truck. You don't want to move much, and if yours is as bad as mine was you wont need too, just because you wouldn't want to side load the front output gear in the T-case. Mine would jump half way around the gear before catching.
And before anyone says anything about taking the retainer off and the gear moving---I know that plate holds the gear in place and with it off the gear will pull alittle bit toward the center of the truck--but this amount would not be enough to cause as much play as I say in the chain, and this is why I said moving it around alot may not be good for the bearings and seals for the front D-shaft.
Any way, good luck with it---just hope this gives you something to look at.
----Byron
 
Well, removing the bearing retainer cover is worth a shot. I will try it tomorrow and see what happens or should I say what I find out. I am hoping it is not the xfer case but guess it cant be nothing simple according to luck.
 
itllmakeit said:
I tried it................

The banging is still there but not as bad as it was but it is now doing it also when I turn to the left but not to the right.

I reckon I will try to do something with the xfer case and see if it is the chain slipping.
Click to expand...
don't turn
 
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