Hello out there, I have a 93 EXPO Wagon(colt vista wagon) AWD that I've encountered a drive train vibration/noise issue.
It's 2.4 liter w/automatic transmission with only 145,00 kms. Everything is fine until I reach a speed of 90 klic's/hr a vibration/humming noise starts
and gets a little worse above 100 and stays even up to 120. I dropped the drive shalf to fine the rear universal joint just about ceased
and the front one very tight. I replaced both universal joints. At the same time I lubed the center joint just after the hanger bearing.
Put everything back together and went for test drive. It was a little better but still had the vibration (very subtle) and the humming noise was still
there. I replaced the hanger bearing (dealer part). It seemed to be much better for about a week. Now it's back. I suspect the center joint
(CV joint) is the cause. I removed the rear section of the drive shaft and left the front part in place. Now I'm running in FWD only and there's
no vibration/noise at all, even at 110 to 130 kms/hr. But, I'm still not certain if it's the cv joint or may something in the rear diff.

Any suggestions/help would be much apreciated. I checked the price for the center CV and it's over 500$ CAN. Both I go further, I wait to see if any of you
have a better suggestion.

I do all my own repairs on several vehicles.

Thanks, Bert. (IMG:style_emoticons/default/unsure.gif)

It sounds like it could be a bad "lombo" joint (you call it "center CV joit). You might have to try another used drive shaft.

But on the subject of the driveshaft, you can't just drop the DS or our AWD system! We have a center differential with a viscous coupling. When you remove RWD, you effectively "open" one of end of the differential and the only thing that keeps you moving at that point is your VS (which isn't very strong).

Was your car extra sluggish when you did this? It should have felt like something was slipping in the drivetrain. If not, your center diff might be locked! Which is a different problem but a problem never the less.

Thanks,

The only thing I noticed that from a stand still position the acceleration was momentarily (a sec or two) sluggish but would then really move easily. You mentioned a center diff, where would that be located? I realize that off the tranny there's the transfer case where the drive shaft is connected. If I disconnect the drive shaft completely from that point I would loose a little oil. I tried that and went for a liitle test drive. The noise and vibration was gone. So, I topped up the transfer case and tried it with only the front portion of the drive shaft with the new hanger bearing in place. Again the test drive indicated no noise or vibration. The lombo seems to be a little stif, so I had cleaned it in solent and repacked it with VC HP90 grease. Put the whole thing back in place and it seemed to work fine, no noise or vibration for a week. Then it came back.

So, looks like you may be right about the lombo. You mention center diff being locked. Do you have an idea how to check.

Thanks again, Bert.

he center hanger bearing can be bad. The bearing race surface cab be "pitted" have scars or scratches that will make it make a terrible noise as it spins. It generally wont be loose or seem bad as in cases when they are worn out which makes it hard to detect.

Well, the fact that it was sluggish off the line is a good sign. This means that it wasn't locked. However, driving like this is VERY damaging for the center diff and the viscous coupling. So while it might have been OK, this might no longer be the case. (IMG:style_emoticons/default/sad.gif)

To check if your center diff has locked, make a very slow turn with your steering wheel all the way to one side. If you feel your tires skipping on the pavement, you center diff is locked. The same things happens to 4x4 truck when they are left in that mode on dry road.

FYI, the center diff is located inside of your tranny. Which means that our AWD trannies have two differenctials: front and center. Plus, we have one more in the rear end (for a total of the 3 diffs).

Our transfer case is pretty dumb. All it does, is changes the direction of torque by 90 degrees. Its ratio is 1.07 (or 1.09 depending on year) to 1.

Thanks gransm. I know what you mean with a 4X4 and front diff in lock mod and you do tight turns, the front wheels tend to hopp. I have an 1980 International ScoutII with lock-o-matics. In free wheel not a problem in 4X4. But if the front hubs are in locked position, that's a different story. the front tendo to hopp on dry surfaces.
I''l try and fine a used drive shaft and see if there's any difference.

Thanks again, Bert (old-scout1980) (IMG:style_emoticons/default/thumbsup.gif) (IMG:style_emoticons/default/liebe011.gif)

By the way, is the viscous coupling in the tranny? I'm going to do a little test with the center joint in the drive shaft. Take it completely apart, clean it
and see if there is any scoring/scratches etc.

Yes, the VC is inside the tranny, just on the outside of the center diff. The good news is that it is easy to get to (if it must be replaced).

Thanks, grndsm. If I resolve this issue I let you know....... (IMG:style_emoticons/default/thumbsup.gif) (IMG:style_emoticons/default/liebe011.gif)

Well good news grandsm, issue is resolved. It finally came down to sending out the complete drive shaft to a speclialist (repair/balance) all kinds
of shafts. They found the unit out of balance as well as one of the universal yokes slightly bent.
So these are the steps that I took:

1 - Replaced both universal joints as they were just about seized, (75$)
2 - Replaced the hanger bearing as it was quite noisy. (90$)
3 - Took apart the flex joint in the middle of the drive shaft, cleaned the ball bearing races (buffed), repacted with HP90 grease (4$)
this was done as there was some stiffness when moving the joint around. I found there were little indentations on the races.
4 - Finally having the drive inspected and repaired. (straigthen and balanced), (220$)

Just returned from a test drive it hums along like a brand new car. So overall it cost me some 389$ and my time.


Hope this helps out someone else with an AWD with a similar issue.

Thanks, OLD-SCOUT1980 (my other nickname)