290 DPA 1990 Knock

"Hello.... I am usually on the

"Hello.... I am usually on the Diesel forum, but thought this question might fit better here. I have 2 drives with A4 props. One makes a chatter knock sound like 2 small blocks of wood being quickly knocked together, while in neutral. When in gear, it diminishes considerably, but is still faint in the background sound of the engine. It clearly comes from the top of the drive. Its now off the boat and going in for repairs. It had a new intermediate housing put on and was shimmed because the big round hole was chewed badly at the top. The U joint was inspected and greased. It has only seen 20 hrs, 5 hrs in gear. Thank you for suggestions as to what should happen next at the Penta Dealer."

'Thank you for suggestions

'Thank you for suggestions as to what should happen next at the Penta Dealer.'

You will get a 2k bill and hopefully a re-shimmed and partly rebuilt upper unit.

"Could the knocking be due mos

"Could the knocking be due mostly to incorrect setup,or the gears or upper bearings? I am looking for advice here to hopefully avoid the dealer saying it was not their incorrect setup.
Thank you"

"If really 'knocking'

"If really 'knocking' it means there are play somewhere that should not be.
Caused by shimming 'error' or wear is to me impossible to say.
It might be gears and/or vertical shaft, it might even be the suspension/ bushings/steering that has play.
The best might have been to let the workshop test out the source with boat in water first."

"Before jumping to a conclusio

"Before jumping to a conclusion that this is out drive transmission "gear/bearing" related, I'd want to check and see if the PDS Bearings or Drive Coupler could be making this sound.
You also mention that the U-joint was inspected and greased! What does "inspected" mean?
(Did anyone actually remove a bearing cap and look at the cross piece?)

Question: What part/piece are you calling the new "Intermediate Housing"???? And why or how did it become damaged???

Ask for a diagnostics inspection.
Make sure that they have identified the problem..... and that the "work scope" and "quote" (not an estimate) will lead to work being performed that WILL correct the problem.
Anyone can throw enough parts at something and eventually correct an issue.
Don't fall for that one! There is no sense in paying for work that does not correct the problem!

."

"Thank you Ricardo... History.

"Thank you Ricardo... History..Everything has been rebuilt in the flywheel housing when engine was rebuilt and boat launched in August. This DP-A drive was rebuilt 3 yrs ago and had a knock from the start. VP dealer said other things causing the noise after drive was reinspected at their shop.
I broke the interm housing where the shift cable attaches when installing drive in July. Upon inspection at a new VP dealer, foung the top of the interm housing where I presume the shims go was chewed, which is why I had the housing was replaced. (20 hrs run time since repair.) Engine with drive removed was run with no noise, so noise is definately in the drive. I do not want problems to grow, so now that the boat is out for winter I am just trying to head off bigger problems."

"I think that you got sold an

"I think that you got sold an ice cube while at the North Pole!

Any chewing or markings to the inside of the Intermediate Housing...... (and I've seen my share of these)..... is usually superficial and will have been caused by a more serious bearing or gear failure from above.
I say "superficial" in-that the area where the shims lay is protected by the simple fact that the Angular Contact bearing (the lower driven gear bearing) and the shims are being pressed against this shoulder surface under several hundred pounds of pressure!
Pretty tough to gawl, scratch or "Chew" up a critical area that is covered by a bearing!!!!! Would you agree????
(I'd love to see this damage to your old Intermediate housing!)

An engine being run with the drive removed may not necessarily eliminate the PDS as the source of noise!!!!
When there is no load, nor any rotating mass attached, the dynamics will be slightly different!
I'm not suggesting that it IS the problem, I'm just pointing out that this may not be a valid means of eliminating it!

I would, however, be safe to eliminate your lower unit from what/how you describe this!

Has anyone replaced the transmission "main drive gear" back-to-back tapered roller bearings? (this can be referred to as the "Bearing Box")
These drives are older now, and since I am seeing more and more of them in need of replacement, I pretty much make this protocol!
If these were replaced........, did they give you a spec sheet on the rolling torque value that they set this up with????

A loose rolling torque value at this set of bearings "may"..... (I say MAY)....... cause a similar noise!
IOW's, any longitudinal movement in this gear may present itself in the form of a vibration and/or clatter or ????
It also won't live a very long life!

Transmission vertical shaft up/down end play is also very important. While I doubt this is contributing to your "In Neutral" noise, you may want to see if they checked and/or corrected this!

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