Grinding/clanking sound from stop?

[rgretzinger]

I decided to get the blazer out and driver it this morning and at the first stop light I approached I gave it some gas and I heard a loud clanking from either the NP 203 transfer case ( it was in 4 wheel drive at the time) or the rear differential. It only seemed to happen from a stop and under moderate acceleration. If i took it easy it drove fine but the couple of times i gave it a little over half throttle from a stop it did it again. This only happened from 0-5 mph, as soon as I heard the noise I let off the gas and slowly proceeded to give it gas again and it stopped. I do have a 10 bolt with gov bomb and haven't had any problems with it yet.. Any ideas of what this might be?

 

[rgretzinger]

The np 203 does have a part time kit installed. It did it in both high and high lock.

 

[diesel4me]

Stretched chain in your NP203???...sounds like it might be...check your U-joints and any CV joint yokes for slop too.,,

 

[rgretzinger]

U joints and cv joints are brand new. Being heavy footed probably dosen't help the chain much. The weird thing is that I locked the hubs and drove it in 4wd this morning to help lube the front diff. It hasn't done this before but since I've bought it I haven't been in 4wd much.

 

[84 k5 blazer]

Motor mounts, fan eating shroud when torquing?

 

[Blue85]

I remember somebody having this problem like 6 years ago, but I can't remember what caused it - only that something in the driveline was binding. The actual sound was coming from the rear driveshaft. They really ring like a bell when you tap them.

 

[rgretzinger]

So when the hubs are unlocked it no longer makes this sound. I am assuming that diesel4me is right. The noise has to be coming from the transfer case and being that it is chain driven and the transfer case is probably 100% original it makes sense. How easy is it to swap out the NP 203 with a NP 205 that is from a a th350 trans?

 

[diesel4me]

When I removed a NP203 from a 77 K2500 GMC with a 454 I had (that had the same type of noise as you describe during a hard launch ) ,and replaced it with a NP205 I had from a 1972 K series with a TH350 ,I had to get a shorter front driveshaft ,If I remember right the rear one still fit OK as far as length but I had to find a rear yoke for the NP205 that would accept the larger 3/4 ton U-joints...the case I had came with the TH350 adapter and ny truck had a TH350 already,so no issues there--if you dont get a T-case with the right adapter and spline count you'll have to swap input shafts and get the adapter you need --best to just get one thats correct used,and just pop it in..

I found a 1969 K10 had the perfect length front shaft that bolted right up with no mods--it was about 23" long cap to cap,and had the right CV joint yoke to maye with the '72 "old" 4 bolt style front yoke on the NP205..

I think I had to cut the tunnel away to let the shifter go into 4 low too,but my trucks had a 2wd cab on it with a body lift and that may have been why I had to enlarge the hole in the tunnel..I still have the NP203 & the TH350 adapter,I never did open it up to see what was going on in it--the noises vanished when I put the NP205 in !..

 

[chalet2506]

How easy is it to swap out the NP 203 with a NP 205 that is from a a th350 trans?

This is an easy swap, but you need new driveshafts. Pretty sure the 205 needs a longer rear and shorter front. Cross member from your 203 will work.

I've got a couple 27 spline 205's and adapters sittin here if you don't have a line on one.

 

[DizturbedOne]

Both of my shafts had to be replaced. I had a 4" lift when I switched to 205

Sometimes the crossmember won't work either, as is

I had to elongate the holes on my NP203 trucks crossmember to get the 205 to fit. I had no tools to do it, so I just grabbed a 205 crossmember from a junkyard close by.

The only difference between them was the elongated holes for universal use in the 205 crossmember vs. very small specific holes for my 203 truck.