Drive shaft questions

[lljanssen]

I had a 1987 K100RT whose drive shaft failed at 97000 mi. I now ride a 2003 K1200GT whose first drive shaft failed at 105000 mi. In both cases the failures involved the U joints, and in both cases I was stranded by the failure (I really hate that). Fortunately there was no signifacant damage to the swingarm--replacing the drive shaft corrected the problem.

The GT now has 202000 mi, leading to the following questions:

-What is your experience? Do drive shafts typically have a 100000 mi lifespan, i.e., should I expect another failure is coming soon?
-I had no obvious symptoms of impending failure. Did you notice any signs that a failure was imminent?
-Are there inspection procedures that might suggest that ad U-joint failure is coming?
-If drive shaft life is 100K, have you done a pre-emptive shaft replacement (very expensive part)?
-I have a Clymers manual and reasonable wrenching skills. Are the Clymers descriptions adequate for a replacement project?
-Any experience with using a used shaft from a reputable supplier?

Any and all responses are appreciated. Thanks in advance for your input.
Larry

 

[52184]

The GT now has 202000 mi, leading to the following questions:

-What is your experience? Do drive shafts typically have a 100000 mi lifespan, i.e., should I expect another failure is coming soon?

I had a shaft failure on 2004GT that had 50k sólo and 30k as a sidecar tug. You should plan on pulling and inspecting the shaft every 24k, paying particular attention to the u-joints but also to the center shaft section, which should be split, cleaned, and regreased with moly grease.

-I had no obvious symptoms of impending failure. Did you notice any signs that a failure was imminent?
-Are there inspection procedures that might suggest that ad U-joint failure is coming?

Increased vibration, but only in the last 40-50 miles of operation. Inspection as mentioned above, looking for notchiness or stickiness of the joints, and verifying that the central portion is greased and moves freely. The shaft on these bikes is circlipped at each end so it’s critical that the center section moves freely to allow for length variance throughout the suspension travel.

-If drive shaft life is 100K, have you done a pre-emptive shaft replacement (very expensive part)?

No.

-I have a Clymers manual and reasonable wrenching skills. Are the Clymers descriptions adequate for a replacement project?

Yes. It’s not necessary to remove the FD to pull the shaft, but you need enough room (height) to swing the drive all the way down. However, it’s also a good opportunity to inspect and replace or regrease the FD pivot bearings. If they haven’t been replaced in 100k they are likely in need of replacing. You need a couple of special tools to properly re-torque the pins and locknuts, like an inch-lb torque wrench and a modified socket for the locknut, but the socket setup can be made inexpensively from a Harbor Freight socket.

-Any experience with using a used shaft from a reputable supplier?

I replaced my shaft with a used one from BeemerBoneyard, from a wrecked RS with only 7k on the clock. The problem with used shafts involve mileage, related wear, and the unknown status of previous servicing on the shaft.

First thing I’d do if this were my bike is inspection, cleaning, and regreasing. That will tell you the status of your current shaft and what does or does not need to be replaced.

Best,
DeVern

 

[drneo66]

It's now five years old, but here are some of my thoughts:

https://forums.bmwmoa.org/showthread.php?91472-2018-%E2%80%93-The-Current-State-of-K75-K100-Driveshaft-and-Final-Drive-Splines-Repair