2002 S10 Blazer 4dr 4WD: it will go into 4HI and back to 2HI without problem. Will go into 4LO from 4HI okay, but upon selecting 4HI I get a loud bang, clank sound like a hammer hitting the driveshaft. Any ideas on this?

Also, the front driveshaft is always engaged although the front differential is free in 2HI. If I turn the front driveshaft by hand, the rear driveshaft also turns. How about this one?


Thanks

 

I assume you have the 3-button switch in the dash since you did not mention having auto4wd. The auto4wd trucks (NV236 w/ 4-button dash switch) have a preloaded clutch pack in the transfer case which results in the front shaft always having some connection to the rear. However, the NV233 (3-button) should completely free-wheel the front shaft when in 2HI.

Is the transmission in neutral when you are shifting ranges (HI to LO or LO to HI)?

 

I knew I forgot to mention something.....my Blazer is the four button model.

And yes I have the transmission in neutral when I shifted out of 4LO to 4HI. I have done this at two separate times....weeks apart...and both times I got the loud clank. I am assuming that something is sticking when coming out of 4LO...just do not know what it is.

Good to read about the clutch pack having preload that would give it some connection to the rear....hate to think that the transfer case has been stuck in 4WD mode with just the front diff not locked for all this time and lots of highway miles.

I changed out all the U-joints as the driveshafts had lots of surface rust from previous owner being on Long Island. After power wire brushing the shafts I gave them both a nice coat of paint, being careful to mask-off those areas that need to stay un-painted.

 

Does it make the clanging noise if you are rolling slowly while making a range switch (HI to LO or LO to HI) with the transmission in neutral?

 

I will have to try a slow roll and see what happens....I will update when I do.

 

Finally had a chance to see what happens....
First time just barely coasting in Neutral, put from 4HI to 4LO...back into drive for 10 feet. Then coasting about 3mph I selected 4HI....and got a CLANG!.

So then drove several miles and found some really loose gravel and went into and out of 4LO twice. The first time was not as loud as the one above....the 2nd time was even less of a clang.

Sounds like this vehicle have never seen much time in 4LO and just needs to be used a bit.

But anything else I should check?????