T case issue?

[Boothby1952]

Good day. As I am not able to diagnose some issues, I would like some help. My 78 K15 has a 208C t case. When putting the truck in gear, I get a loud and rough banging sound. I checked the universal joints and they seem tight with no slop, but I can turn the rear driveshaft about an inch. I am assuming the t-case is going, if not gone already. Any other possible causes I should be considering? Thanks in advance.

 

[Grit dog]

Yes, all other causes except the obvious, u joints, if you say those are good.
First, you have a franken truck drivetrain so no idea what else was or wasn’t done or what junker the parts got pulled from. (208 cases didn’t come in causes until the 80s models)
Second, the rotational play in the driveshaft is more likely the rear end and it’s not necessarily bad.
Third, more likely the trans is going into gear harshly than the t case making that noise when you just shift it into R or D at an idle.
Last, what other symptoms? Does the t case work properly in all ranges, how’s the oil? How’s the trans? Verified it’s not slamming into gear? Same with rear end.
A 4wd will have inherently more slop overall in the drivetrain due to far more moving parts than a 2wd. And your description is vague and not really quantifiable.
Also it’s the rear axle that doesn’t rotate if the vehicle is not moving. The trans and t case will spin all day if unhooked from the axle and not in Park.
Hope this helps

 

[nvrenuf]

To add...

Has the engine idle changed? A higher than normal idle (possibly caused by vac leaks, etc.) can cause it to be harsh going in gear.

 

[Boothby1952]

Thanks for the input. Got some detective work to do now.

 

[Snoots]

Chock the wheels and disconnect the rear driveshaft. Does it turn that inch or so? X-fer case. Turn the Yoke at the pumpkin. Does it move an inch or so? Rear gears.

 

[Boothby1952]

How much allowable play in the pinion yoke is tolerable? Pulled the diff cover and found no metal in the gear oil, everything seems tight when spinning the wheels but I can rotate the yoke about 1/4" + - so I'm assuming pinion bearing?