NP205 - grind - pictures inside.

[K5_Fla]

K5 Blazer – 6in suspension lift. TH350 married to NP 205.

Issue- when I’m riding in 2 wheel drive at highway speeds… and let off the gas.. I get a grinding noise coming from the case. I’m 100% it’s coming from the case. 4x4 works fine when I need it, and no noises there.

Here is what is new.
U joints in all the drive shafts
Front drive shaft is completely new
Rear slip yoke
Polly crossmember mounts are new
Transfer case drop down spacers for crossmember.
New Royal Purple gear oil in case
TH 350 was rebuilt solid not long ago.

Side note – the case shifter was real sloppy shifter – had a worn spacer. So I changed the spacer (where the linkage bolts to the case) and used a new one… a little thicker. Shifter is nice and firm now. See pic. But… when I back up in reverse I have a “ticking” sound coming from the transfer case. Just started when I put on the new spacer.

I guess the first question is does everything look correct (angels, etc) in these pictures below? Should I remove the crossmember spacers?

 

[JDNobodi]

Hmm, You have the np205 that is mated to the th350. I've heard the coupler between the two when it wears out makes a racket.
Too bad you have the slip yoke 205 otherwise I would tell you to start removing drivelines to see if the problem is in the front or rear.

 

[K5_Fla]

so the slip yoke 205 is a good thing then? I dont have a clue about this stuff... other than the NP205 is probably the best case out there.

Oh yea.. I did go through and tighten all the bolts that hold any braces... the motor mounts, etc. Nothing was really loose

 

[Burbdood 74]

so the slip yoke 205 is a good thing then? I dont have a clue about this stuff... other than the NP205 is probably the best case out there.

Oh yea.. I did go through and tighten all the bolts that hold any braces... the motor mounts, etc. Nothing was really loose

Since you have a slip yoke on the 205, if you remove the rear drive shaft, you're going to lose a lot of fluid if you drive anywhere as it will spit out the top where the yoke goes. If you have a fixed yoke that you bolt the drive shaft onto it, you won't lose any fluid at all.

Of the two, the fixed yoke is a much better design because if you were to lose a u-joint on the road, you could remove the drive shaft, lock the front hubs, throw it in four wheel drive and drive home essentially as a front wheel drive truck without losing any fluid from the t-case at all.

 

[folkenheath]

Should I remove the crossmember spacers?

Yes, I would remove the spacers if I were you, that may help the rear d-shaft angle, but it will hurt the front. It is also not good for the frame, could potentially cause cracks.

Do you feel any slop on your front or rear outputs? (keep in mind there can't be any load on them, in neutral with the wheels chocked should unload them.)

 

[diesel4me]

I had a '69 Cougar that had that type of noise when de-accelerating from highway speeds,and replacing the u-joints did nothing--I found out later that the pinion nut on the diff had loosened up,after I tightened it properly,the noises and vibration vanished..I would have bet money it was the tranny too,not the rear end,thats where the vibes seemed to originate...they can be amplified and travel thru the driveshaft,and make it sound like they originated elsewhere...On my Chevy van,I noticed similar noises and vibes when I replaced the rear axle,and neglected to replace the nylon pads between the spring pads and the leaf springs..vans seem more prone to noises being a big echo chamber right over the differential,I heard pinion bearings making whirring and scoring noises,till I put new pads on the spring perches,they must insulate it...

 

[down4thakrown]

ya my th350/205 makes the same noise, i just have the fixed yoke tcase. been doin it since i installed them and havnt had a problem.

 

[newoldscottsdale77]

my 205 hums at highway speeds after i let off the gas, it operates fine so i ignore it now, i read online somewhere that this was normal due to vibration in the driveline, that was with my 35's, 37's and now my 39.5's