Occasionally, I get a clunk on shifting from park to reverse?

MARKVIII1

MEMBER
1994 LINCOLN MARK VIII
4.6L
V8
2WD
AUTOMATIC
197,000 MILES

No visible play in U-joint when under the car and moving shaft by hand. Occasionally, when starting the engine there is perhaps a one second or less hesitation between cranking and engine turning over, where I can feel what seems like movement of driveshaft (not a clunk). Lastly, have read where a clunk of this nature can be caused by the slip yoke needing internal lubrication of the splines. Thanks so much. Await your thoughts.

5 Replies

MOTOR MASTER

MECHANIC
279 POSTS

Hello my name is Dave.

As an owner and fan of the VIII your question definitely caught my attention. If the slip yoke was causing this is issue it would most likely need replaced however since it has extremely limited movement it would be unlikely to be the issue. The most common cause of this problem I have found with our cars is in the transmission, the valve bodies of this generation of the 4R70W were not the best and are prone to issues including the chunking you have described, usually going into reverse. If it is intermittent I would recommend servicing the transmission, changing the filter and adding Lucas Stop Slip additive.

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Tuesday, May 25th, 2021 AT 5:07 AM

MARKVIII1

MEMBER
4 POSTS

Hi Dave,

Thanks so much for your quick and informative reply. Appreciate it. I will try the Lucas product you suggested. I guess this suggests two more quick questions.
1) Even with the Lucas product, is this a worsening situation, or could it be a fix for very limited driving?
2) Would a new valve body be a more permanent fix for this particular situation, realizing that with a Mark VIII of this age other transmission concerns could come about?

Thanks so much Dave. Look forward to your reply.

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Tuesday, May 25th, 2021 AT 6:33 AM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Can you please shoot a quick video with your phone so we can see what's going on? that would be great. You can upload it here with your response. Here is how to service the slip yoke which can cause a cluck. This video shows the job being done on a similar car but the process is the same.

https://youtu.be/p2snOCyqVMY

Please let us know what happens.

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Tuesday, May 25th, 2021 AT 12:12 PM

MARKVIII1

MEMBER
4 POSTS

Can't video a clunk. Need Dave to reply to my reply to his first answer. At that point the conversation was about a possible solution involving the valve body. Awaiting reply.

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Tuesday, May 25th, 2021 AT 2:13 PM

MOTOR MASTER

MECHANIC
279 POSTS

Sorry for the delay. A lot of the time the problem is varnishing on the valve causing it to stick and the Lucas is pretty effective at the varnish so if it clears it up it should be a lasting repair. As far as future issues with the transmission they will most likely be valve body related however I don't feel there is enough of a common issue to replace it as a preventive measure. The most common issues are sticking valves and broken accumulator springs, the last one is replaceable without dropping the valve body so is not a terribly extensive repair and usually causes hard shifting which, as a rule won't damage the hard parts of the transmission.