Is my transfer case toast?

[clutch2k3]

Are you saying the transmission was in gear, but something was slipping so the vehicle didn't move? That's an important piece of information. I guess it's possible you have a worn shift fork and the case is getting stuck between modes. You should verify that the shift linkage is adjusted correctly. https://ck5.com/forums/threads/208-linkage-adjustment.339528/. You can manually shift the case without the linkage for troubleshooting.

You might have better luck going all the way from 4LO to 2HI, rather than trying to shift 1 step at a time.

Yes, the transmission was in D, the TC in 4H and the hubs were locked but the truck wheels wouldn't turn. I was thinking posible shift-fork issue myself. Looks like there are plastic wear items on those forks.

Are these the stock diff's? first pic is rear and second pic is front. I named the photos too in case y'all can see the file names.

 

[Blue85]

Those diffs did come stock, so they could be original, but who knows what's happened over the last 3.5 decades. They're both 10-bolts - front open, rear G80 gov-lock. While they're open, find the stamping on the edge of each ring gear, which tells you the ratio.

Yes, the plastic pads can be replaced. If neglected long enough, the forks themselves wear.

 

[clutch2k3]

so with the diffs being stock, I think can put the mismatched-gearing theory to rest.

 

[fourwheelerjeff]

so with the diffs being stock, I think can put the mismatched-gearing theory to rest.

without confirming they match I would say no. these Blazers came with different ratios over the years and even in the same year model. I once bought a Blazer that the rear axle had went out and the previous owner replaced it. it had a 3.07 rear and 3.42 front yet they were still stock axles.

 

[Blue85]

While they're open, find the stamping on the edge of each ring gear, which tells you the ratio.

so with the diffs being stock, I think can put the mismatched-gearing theory to rest.

Nope! Just because they're stock-type doesn't mean they haven't been swapped. It happens all the time that rear gov-locks blow up and someone gets an axle assembly. In some of those cases they use whatever they find, even if it doesn't match. Of course, even if they swapped in different axles, that still wouldn't prove that they match.

Like I said, that vehicle is about 34 years old and you've only had it for 3 months.

 

[fourwheelerjeff]

While they're open, find the stamping on the edge of each ring gear, which tells you the ratio

this is the best way to be for sure

 

[tarussell]

It’s difficult to tell from your pics being at a slight different angle on each one but it appears that the ring gear thickness is most likely different and that means you most likely do have different ratios front and rear.
This means that one of the axles have been swapped out at some point just as mentioned earlier by some of the other fellas and most likely it was the rear axle since that type of differential is known for breakage.

Get good clear pics of ALL the numbers on each ring gear ( spin them all the way around to make certain you capture all ) and we’ll help you with what you have.

 

[clutch2k3]

I just replaced the fluid and resealed the front last week.

I'm thinking I could put a piece of tape on the sidewalls, put the trans in neutral, lock the hubs, put the TC into either 4H or 4L, spin a wheel and count tire rotations. Would this work? Should I only Jack up one side, e.g. just the driver's side, to account for the open diffs?

 

[Wes Harden]

it will work. yes leave 1 side on the ground. What is the rear ratio ?

 

[clutch2k3]

Is 351 a valid ratio? Pics are from rear diff, front is sealed up ATM.

 

[Wes Harden]

no but 3.41 or 3.42 is

 

[6872xtc]

without confirming they match I would say no. these Blazers came with different ratios over the years and even in the same year model. I once bought a Blazer that the rear axle had went out and the previous owner replaced it. it had a 3.07 rear and 3.42 front yet they were still stock axles.

I bought an old suburban that had 3.73 rear and 4:10 front, with a 203 cuz it was a '75.
As you said, it happens.

 

[clutch2k3]

Thanks for the help so far.

For reasons I pulled off the front diff cover (FYI jacking up only one side doesn't work). I attached a pic of the numbering on the front ring gear.

I'm reading 1235128 12 42 9 88 on both ring gears.

 

[Wes Harden]

did you lock both hubs ? yup same gear ratio both axles

 

[clutch2k3]

While watching the front tire that had tape both on the inside and outside of the tire, I spun the rear wheel 1 time, 2 times and finally 5 times and the front wheel rotated exactly in sync with the rear wheel 1 time, then 2 times then 5 times. Also, the ring gear numbers match exactly. I am 110% sure the front and rear diff ratios match.

All 4 tires are BFG AT T/A 32" tires and all 4 tires have date codes corresponding to 2019 and all 4 tires have the same amount of wear.

If y'all made it this far, might be worth re-reading the problem description and looking at the pics a second time as this problem was not due to mismatched diff ratios nor mismatched tires.

 

[Blue85]

If y'all made it this far, might be worth re-reading the problem description and looking at the pics a second time as this problem was not due to mismatched diff ratios nor mismatched tires.

Of course! Even more so, it's worth you re-reading ideas already presented in this thread.

 

[tarussell]

It is difficult to administer proper advice over the internet but so much of your description suggested intense binding.

Let’s just cut right to it and post up a video with quality audio so we can all hear the ticking noises you are hearing.
If possible please don’t lock your truck in to 4WD on pavement - that should not be done as SOP especially not when new to the workings of a 4WD system.

A good and informative video might help eliminate the questions from complaint to pinpoint a fix.

 

[clutch2k3]

This ended up being user error. I was driving in our cul de sac in a tight circle on pavement which caused the front & rear driveshafts to rotate differently, exactly mimicing mismatched gear ratios. Since all the seals were spewing ATF everywhere, I rebuilt the transfer case and verified that the chain, gears, bearings, shift forks, and everything else was in great condition (I now love the NP241C!).

Thanks a lot for all your great advice and apologies if I came off dickish, I was fustrated.

Not to start any arguments, just for anybody else wanting to test their 4WD on pavement for some reason: After rebuilding the transfer case and first testing 4WD on grass, I drove up and down the street, on pavement, in a dead straight line, in 4H & 4L, with the hubs locked, only a few hundred feet, and the transfer case worked just fine. For any other newbs reading this, I would only recommend driving in 4H/4L on pavement for very short distances, no more than a few hundred feet at the most.

 

[Blue85]

the ticking got even louder and then I started hearing clunking and what sounded to me like gear grinding.

I rebuilt the transfer case and verified that the chain, gears, bearings, shift forks, and everything else was in great condition (I now love the NP241C!).

OK, so what was causing these noises? It's normal for the tires to slip and jump a bit when the 4WD is binding, so I could buy the clunk being some loose thing getting loaded and unloaded, but grinding?

 

[clutch2k3]

OK, so what was causing these noises? It's normal for the tires to slip and jump a bit when the 4WD is binding, so I could buy the clunk being some loose thing getting loaded and unloaded, but grinding?

no metal chunks at all in the transfer case, front diff, rear diff, or trans pan. been driving it around up to 50 MPH without issue. Need new tires to go faster. The current tires which have flat spots are getting replaced tomorow. maybe at highway speeds something else will shake out? Fed her all the onions 4 times, up to 45 MPH, too.