I have a 1987 K5 Blazer, 4" lift, 35" tires. 700R4 with 208 transfer case. After the lift (a year ago) the driveline was not lengthened, the lift extended the slip yoke only out an inch, maybe that's too much.

Recently I replaced the 3.42 gears with 4.10's, all new bearings and pinion yoke. I also replaced the open rear with an Auburn posi. Good pattern on rear gears, backlash and differential and pinion preload to specs. U joints replaced.

Now back on the road. Driving under power at 60 mph, seems to be quiet, as soon as let off the gas, lots of noise until I hit 40 MPH.

Yesterday I ran it in the garage on jack stands, 60 mph, deep growl appears to be from transfer case under power and off the gas. At first I am thinking I screwed up the rear gear setup, but rear axle is very quiet, all the noise is in the transfer case area. The transfer case did not appear to make any noise before the gear swap, now it sounds like it is ready to grenade.

My question is can an improper rear axle set-up transmit noise to the transfer case?

Or, is the new tight rear end, showing fault with the transfer case or driveline, the old rear had a lot of slop?

How can I tell if it's the transfer that's bad?

Sorry for the long post, sounds like it's time for a rebuild, but I want to make sure the it's toast first. I don't understand why it is noisy now, maybe it's been on it's way out.

Cheers

it could be transmitting the noise up the driveshaft from the rear..

Drain the fluidin the t-case and see how it looks, run it in 4x4 and see if noise changes.

Its possible t-cse is gettin tired

You never mentioned anything about the front differential.

How can you change the gear ratio in a 4WD vehicle in the rear without matching to the front?

That would certainly create some transfer case issues in my book.

Loki I did both. I just didn't fall off the turnip truck ):h .

I only mentioned the rear because that is where the problem is, 2WD, the noise is the same in 4WD

Loki I did both. I just didn't fall off the turnip truck ):h .

I only mentioned the rear because that is where the problem is, 2WD, the noise is the same in 4WDWell all-righty then, tear out that transfer case & have at it. :ro)
There are lots of input &/or output bearing applications that get loaded up only on deceleration, either way, it sounds like the transfer case is probably going to have to come out & come apart.

Loki,

I meant no offense with my comment, I should have stated my experience in the post, which is hardly a beginner. Just have never dealt with lift related driveline issues before. I just want to make the right diagnosis without throwing a bunch of money at it.

My thinking now is that the driveline is just too short. Why it does it now is what stumps me. I have always had a little shutter on take off, but has been vibration free (maybe it was always there, just didn't feel it). I am thinking the yoke is too far out on the splines. It is a 7" yoke, but 2" are showing, leaving only 5" inside.

Your thoughts on that.

Thanks.

coulb be just a driveline vibration. By going to higher gears the driveline RPM has gone up quite a bit. After installing gears did you "get on it a bit"(as I would have) just to feel the difference? If so then see if you didn't pretzel the driveshaft. If noise is iso'd to T-case, first thing to check is fore and aft play, I've seen my share of 208 cases eat the front thrust bearing

No, I have been easy on them, want to make they are broke-in before wheeling.

I have come to the conclusion the driveline is just too short, I believe the TC slip yoke is too far out. Lot's of up and down play in the yoke, when I push the yoke in where it belongs, it's nice and tight.

I think you are right, higher shaft RPM's.

I am going with a CV joint set-up driveline to eliminate the high angle problem and lengthen the shaft.

No offense taken friend. ;)

But this thread is beginning to get a little confusing. :confused:
What I mean is, first there are references to a noise issue (ie-deep growl) & then later to a driveline vibration. There is a difference in procedures for the diagnose of each (or both if combined).

I thought you were dealing with a noise on deceleration that you had already isolated at the transfer case?

Loki, the driveline is not out of balance, at least before I lifted the vehicle, it ran true without any noticeable vibration. After I lifted the vehicle, it pulled the driveline out of the TC by and inch and a half, plus increasing the angle. Why it's making the noise now after the gear changes, is beyond me.

Being out to far on the spines and the rear bushing, there is a lot of up and down side to side motion at the front of the driveline. It's probably wearing out the rear bushing.

I need a longer driveline anyway. I have talked to others on the K5 Blazer site, with similar noise issues, the consensus is too short driveline. We'll see.

I have an appreciation for what you tech's go through in diagnostics.

The problem with any "slop" in the slip yolk area, is that any additional load/imbalance induced there will be multiplied as it transmits itself up the transfer case output shaft, putting much stress on any bearings along or at the other end of the shaft.

Unfortunately, then it becomes an internal transfer case issue.

Hope it all works out easily for you though.

So when I was running a too short driveshaft (slop in the slip yoke), it could have damaged the output shaft bearings, or they were already on their way out.

So I will most likely be overhauling the TC as well, but driveline is first, then we will see.

Seal and bearing kits are pretty cheap, so it's not that much of an impact anymore.

Thanks.

Pull the yoke and look inside for signs of wear.