Delayed "thunking" shifting into 3rd gear

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Feb 27, 2019 | 03:19 PM

SHPR543

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5th Wheeling

Joined: Oct 2017

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Delayed "thunking" shifting into 3rd gear

I have had no issues with the transmission, but I recently noticed when it shifted into 3rd gear there was a thunking noise coming from the rear end. It seems like the transmission had already shifted but then there was the noise coming from the rear end. It doesn't always seem to do it and there doesn't seem to be a rhyme or reason for it...I'd say it happens more often when the transmission is cold. I have no other shifting issues, all other gears seem to be fine. I got underneath, I do not notice any leaks at all. Any thoughts or anyone experience something similar?

Feb 27, 2019 | 08:25 PM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

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From: SE Florida

I have some insight on this. When I was a 5R110W engineer I investigated this because my development trucks did this. Some were worse than others.

It's the intermediate one way clutch. Some do it worse than others, and depending where the sprags are in relation to the race when the clutch engages. If they have a large number of degrees to traverse before they engage you'll get a clunk. If they are close to where they engage you won't get a clunk.

The good news is that it won't harm the transmission. If you want to fix it you can rebuild the trans with an intermediate one way clutch from a V10 trans. That clutch has the same torque capacity, but fewer degrees movement to engage.

Feb 27, 2019 | 11:10 PM

SHPR543

Thread Starter

5th Wheeling

Joined: Oct 2017

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Thanks Mark...only on FTE can I get a response from a Former Ford Automatic Trans Engineer!! It's good to know it wont hurt my transmission...I had fears of a major issue, so I appreciate the information. I do have a feeling this will drive me crazy, so I suspect I will have it rebuilt at some point like you said...Is this an expensive FULL rebuild or is it a modification to add the one way V10 clutch? Just wondering budget wise...

Thanks again Mark!

Feb 28, 2019 | 08:23 AM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,717

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From: SE Florida

It doesn't take a full rebuild. The V10 one way clutch is a direct replacement. The trans has to come out and get torn down most of the way. Then the one way clutch is swapped and the trans is reassembled.

Feb 28, 2019 | 03:51 PM

87crewdually

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From: So. Jersey

Feb 28, 2019 | 07:26 PM

TooManyToys.

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Quote:

Originally Posted by Mark Kovalsky

....... If you want to fix it you can rebuild the trans with an intermediate one way clutch from a V10 trans. That clutch has the same torque capacity, but fewer degrees movement to engage.

So it sounds like there was an intent to have more degrees with the diesels? Just trying to figure out if changing it is working into a new problem or just initial overthinking at launch.

Feb 28, 2019 | 08:54 PM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,717

Likes: 2,642

From: SE Florida

The higher tolerance one way clutch was the original 5R110W design. When the 5R110W was added to the gas engines the clunk was WAY more noticeable. Instrumentation showed that the vibration induced into the truck was the same in the diesel as the gas engine, but the diesel had so much other noise and vibration that manglement decided that keeping the original clutch was acceptable for the diesel, but not the gas engine. I didn't think it was acceptable in either, but I didn't have a vote in the decision. That was done way above my pay grade.
Changing the one way clutch to the lower lash gas engine clutch is only detrimental to one thing: Cost. It won't cause a problem in the trans, it's actually in the direction of better relaibility. The lower lash will introduce lower shock into the trans than the higher lash diesel part, but the difference is small enough to be negligible.