Transfer Case trouble?

[77 Stepside Morph]

My '77 K10 with full-time 4wd makes a clunking noise when I put it into drive and I am wondering what is the best way to troubleshoot the problem.  With the truck in park,  I rotated the driveshafts by hand to see if there was any slop on the U-Joints and everything seems tight.  

What should I do next?  Did I even check the U-Joints the right way?

Appreciate any help,
John

[77 Stepside Morph]

I started looking into the problem and here is what I found:

The motor and trans mounts are solid and didn't move very much under load.  The U-Joints all looked great and didn't make any noise as I rotated the respective shafts with the truck in neutral.  There was obvious slop in the front driveshaft that made me wonder if there might be a problem here.  The snag is that I didn't remove the driveshafts to inspect the joints.  

(What was I thinking?) I had my 16 YO daughter put the truck in drive and then back in reverse with the truck running and her foot on the brake (and E-brake on) while I inspected the drive components.  The clunk noise was definitely coming from the front end as the truck's gear were changed from reverse to drive.  

So, does that implicate the differential or the front output  of the transfer case?  Should I next remove the front shaft to check each part for slop?  What is the best way to proceed?

Thanks,
John
'77 K10 4x4
groups.msn.com/VintagePon...kpage.msnw

[oscarone]

Sounds like your on the right path.  Check the front shaft u-joints first...just because there easy to get to.  Also, the 203(I don't know if you have a part time conversion) is chain driven.  The chain will wear out and get "sloppy".  Do you hear the clunk when changing gears and only in 4x4, or, is it in 2x and 4x?

[77 Stepside Morph]

The U-Joints all look pretty good and don't seem to have any slop.

I don't have the part time conversion,  but I do have front locking hubs,  so it is full-time 4WD.  Is there some way that I can troubleshoot the problem by unlocking the hubs and putting it into 4WD Low or ??   The sloppy chain sure sounds like a good possibility.  Any other way to narrow it down?

Thanks for the help,
John

[oscarone]

If you have manual hubs (that is, you have to get out and turn them by hand)you have a part time conversion.  Here is one way to know for sure.  Your t-case has HI LOC, HI, N, LOW, AND LO LOC.  Normally in all positions except N you are in 4 wheel drive.  With the part time conversion the HI position becomes 2 wheel drive.  With the hubs in FREE put the case in the HI position.  Drive the truck and have someone watch the front drive shaft.  It shouldn't turn.  In fact you don't even have to drive it.  Just crawl under and see if you can spin the front drive shaft by hand.  If so, you have a conversion.  There are two different conversions.  One changes the entire output shaft and is suppose to be the better one.  The other changes a set of gears..This one I have heard can also get sloppy after a while and cause noise.

[77 Stepside Morph]

I pulled the cover tonight and confirmed th athere was a huge amount of slop in the chain.  See my post on Transfer Case R&R...

John