1995 3000GT VR-4: PST 2-Piece CFDS Squeaking Issue


The Infamous Trojan Rabbit Sound

Remember the sound that Monty Python's Trojan Rabbit made as it was being wheeled into the rude Frenchman's castle in "Monty Python and the Holy Grail"? I never thought my car would make those noises!



Initial Problem Description:

The problem is that there is interference between the metal part of the front section of the driveshaft and the rubber in the carrier bearing support once rubber support bears some of the weight of the shaft. When there is no weight on the rubber support, there is no interference between the shaft and the rubber, but the clearance is REALLY tight.

The interference is such that an audible squeaking can be heard coming from that carrier bearing area. I first noticed the squeaking when I allowed the engine to idle in gear with all 4 wheels off of the ground. I have video of this (link at bottom). Thinking that perhaps things just needed to sea t properly, I drove the car around my neighborhood a bit to see if the squeaking got better. The squeaking gets worse under engine braking, and it is minimized (but not always eliminated) under acceleration (load). After driving it a few miles at low speeds, it has gotten better - to the point where it really only squeaks under engine braking. It's still there; and even if not a functional problem, it's embarrassing. Other than the squeaking, the driveshaft seems excellent, and I'm pleased with the improvement from the lightened shaft. Also, I found that by spraying a tiny bit of water (or WD-40) on the lower part of the rubber support, I could make the squeaking stop for 30 seconds or so. Thus I'm confident that the squeaking is entirely due to the driveshaft interfering with the rubber in the support.

I pulled the rear section of the shaft off and removed the carrier bearing support to examine it. There was a little (tiny) bit of black gooey residue along the entire circumference of the front driveshaft section (near the rubber carrier bearing support), and I didn't see any high spots in the welding or anything else abnormal about the end of the driveshaft. As for the rubber support, the shaft has worn a groove in the rubber about 2" long, 1/8" wide (at its widest), and about 1/16" deep. This is in lowest part of this support, where it bulges out slightly when the weight of the shaft is supported by it.

As far as I can tell, the interference shouldn't have anything to do with my specific car. (In any case, I know my engine mounts are good, and the chassis isn't bent or anything.) The location of the front shaft relative to the rubber support seems to be directly related to the position of the carrier bearing on the shaft. Since the shaft can slide along the splines in the transfer case and the splines joining the front and rear sections of the driveshaft, I don't see how the interference could be eliminated by anything other than relocating the carrier bearing on the shaft. I talked to the manufacturer, and the carrier bearing is located on the shaft by pressing it against a shoulder on the shaft; thus, it should be located in the same place on every shaft.

The manufacturer has reported to me that they have sold "many" of these shafts, and the only cases (2 or 3) where they had issues with the 2pc shafts squeaking were when the customer had the carrier bearing support mounted backwards. I'm absolutely sure that my bearing support is mounted correctly. Since the stud on the driver's side of the car is significantly higher than on the passenger's side, there's only one way to mount it on the studs and not have the support totally cock-eyed.

Here is the video of the driveshaft in motion while the car is on jack stands:

Driveshaft Video

Dial-up beware, it's about 1.2MB. Note that you'll need Windows Media Player v9 to view it.


Follow-up Post:

... I tried using up to 4 washers on each side to space the carrier away from the chassis. That made it slightly better, but there is still rubbing and squeaking. I'm not comfortable putting any more washers on there because the nuts are already at the very ends of the threads on the studs. If I put more washers on there, I'd be losing the engagement of some of those threads, and I certainly don't want the carrier falling off on the road!

I talked to Mark at PST today about these problems I'm having and told him that others are reporting the same things on this forum. I have talked to him several times this week, and have discussed the things I've tried to fix the problem on my own. My conclusion (and apparently Mark's as well) is that a spacer between the front tubing and the carrier bearing would solve the problem completely. This would locate the carrier bearing slightly (1/4" to 3/8" ?) farther away from the tubing of the front section of the driveshaft. Hopefully this would make it almost impossible for the rubber to touch the shaft. Further, there seems to be plenty of adjustment room to accomodate the spacer in both the transfer case yoke and the splines that join the two halves of the driveshaft.

They're going to ship me a replacement driveshaft with the new carrier bearing spacer (hopefully by Monday, so I can have it before next weekend). I'll give that a shot and post back about what I find.

As a side note, Mark at PST gave me the impression that they had only heard of a few isolated cases of the squeaking/rubbing problems and the "arrow points toward the rear, not the front" issue. I don't think PST knew there were significant problems and just ignored them, but I know others have been buying stuff from them for a while and may have more info. In any case, so far for me, PST has been very accomodating and I'm pretty impressed with their customer service. Assuming that this bearing spacer fixes the issue, I'll have no problems recommending them to others since they've made a real effort to ensure that I'm a happy customer.



Resolution:

Please see the redesigned shaft section on the previous page, which you can access by clicking the "Back" button on your browser or by clicking here.


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Last Modified Wed May 12 18:25:39 2004 Pacific Daylight Time