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What spins in neutral

ryanm91

New member
Okay so after a year i finally found the time to do some diagnoising on my boat.

boat is a 1968 larson lapline with 289 interceptor and eaton outdrive (has volvo tag and appears to be a aq270)

Assuming the pds housing is a borg warner because it was single PDS bearing with pilot bushing.

Things done so far
replaced bellows (ujoint bellow was cracked)
replaced ujoints and they rotate freely
replaced single sealed PDS bearing and pilot bushing
inspected flexplate and coupler. no slop in any after reinstall of engine and pds housing.

youtube video of noise
https://www.youtube.com/watch?v=KUDiz30Fukw

This leads me to believe that something in the upper unit transmission has gone bad.

Does the vertical shaft spin in neutral? I assume the input bearing what the yoke rides on could be the culprit or chipped teeth. I guess what im asking does anything in lower unit spin in neutral.

Fluid was full and didn't have any metal shavings in it or water contamination.

I will admit besides ujoint bellow being cracked and ujoints were full of water one other thing that leads me to believe it is the transmission. The day before the noise appeared i was backing out of the dock and didn't have drive fully down. As much as i explained to my father that the only way to prevent the drive from drifting upwards in reverse is to have it full down so intermediate locks on the pin in the transom. The stern drive smacked upwards that day and i believe the conical bearing that the yoke rides on could be the issue or it chipped a tooth. The boat has had minimal run time since trying to diagnose the issue.

Am i on the right track that im probably looking at rebuilding the transmission? unit makes noise in gear and in neutral and doesn't matter on turning movements and noise is with drive in full down position.

Just looking for some guidance on where to investigate next.
 
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Okay so after a year i finally found the time to do some diagnoising on my boat.

boat is a 1968 larson lapline with 289 interceptor and eaton outdrive (has volvo tag and appears to be a aq270)
At that age, it's more likely to be a 250.
When I look at the video, I see tell tale signs of 250!

By the way, you are very brave to have your hands near the propeller while the engine is running!

Assuming the pds housing is a borg warner because it was single PDS bearing with pilot bushing.
Possibly a bit early for Borg Warner.
I'd need to see a few photos.


Things done so far
replaced bellows (ujoint bellow was cracked)
You will extend the life of the drive shaft bellows if you will store the boat with the drive fully down and aiming straight forward.

replaced ujoints and they rotate freely
You mean bearing crosses?
(U-joint [universal joint] is the sum of all components)

replaced single sealed PDS bearing and pilot bushing
The Volvo Penta/Eaton PDS adapter housing should be equipped with a grease port and grease fitting or grease cup.
If so, you would use an "Open" bearing, not a sealed bearing.


inspected flexplate and coupler. no slop in any after reinstall of engine and pds housing.

youtube video of noise
https://www.youtube.com/watch?v=KUDiz30Fukw

This leads me to believe that something in the upper unit transmission has gone bad.

Does the vertical shaft spin in neutral?
NO! Neither vertical shafts will spin in neutral.

I assume the input bearing what the yoke rides on could be the culprit or chipped teeth. I guess what im asking does anything in lower unit spin in neutral?
NO!

Fluid was full and didn't have any metal shavings in it or water contamination.

I will admit besides ujoint bellow being cracked and ujoints were full of water one other thing that leads me to believe it is the transmission. The day before the noise appeared i was backing out of the dock and didn't have drive fully down. As much as i explained to my father that the only way to prevent the drive from drifting upwards in reverse is to have it full down so intermediate locks on the pin in the transom. The stern drive smacked upwards that day and i believe the conical bearing that the yoke rides on could be the issue or it chipped a tooth. The boat has had minimal run time since trying to diagnose the issue.
There are two tapered roller bearings within the bearing box.
These are very tough bearings.


Am i on the right track that im probably looking at rebuilding the transmission? unit makes noise in gear and in neutral and doesn't matter on turning movements and noise is with drive in full down position.


Just looking for some guidance on where to investigate next.
Do the same thing again, and use a mechanic's stethoscope against the transmission case.
Move around and see if the noise is more pronounced in a certain area.

Next, drain the gear oil (which should be 30W engine oil only) and remove the eccentric piston housing.
Have a helper rotate the engine while you look at all gear teeth.


You may also want to further muffle the exhaust as to eliminate an exhaust sound that that might be mimicking a mechanical noise.
 
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Ricardo I knew you'd appear. Im down by Salem, Oregon.

Yes i meant i replaced the crosses with new spicer units.

The PDS housing after reading many posts doe not have a grease port, cup or anything. AND the annoying part it is a single PDS bearing that requires engine removal. held on shaft with a snap ring and then a snap ring on the engine side to hold shaft and pds in place, it had a single seal on aft side.

The drive does get stored in down position when not in use.

When the drive was off i fired motor for brief second and the noise was gone. So i thought for sure that PDS/bearing crosses would've been the issue since there was no slop or leaking on the upper gearbox.

I will go check the teeth on the upper gearbox and see if that where the rattle has come from.

The transmission itself did not grind nor have any evidence when i had removed the drive to do crosses. But i am happy to hear that if it's a noise in neutral and in gear it would be upper unit related. Both a stick and hand placed against the upper gear unit it feels like someone is tapping a hammer.
 
It’s possible that you may have a chipped gear tooth.
It is also not cost-effective to buy a new gear set for this.

Keep in mind that the 250 is a small bearing transmission. This means that it must be replaced with another 250.
It’s also imperative that you go through the shimming process!


.
 
yep i pulled shifter apart and theres the missing tooth and undoubtly the knocking noise.

so you're saying my options are get another 250 transmission or swap like an entire 270 on.
IMG_4691.jpg
 
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yep i pulled shifter apart and theres the missing tooth and undoubtly the knocking noise.
I would say so!


View attachment 24854


so you're saying my options are get another 250 transmission
Yes, if you can find one!
Be careful, not all sellers know what they have for sale!
I've seen many sellers misidentify their parts, calling out that a transmission fits 250, 270, 280, 285, 275, 290 etc.
It does not work like that!
There are 3 driven gear bearing retainer sizes to chose from.


or swap like an entire 270 on.
Yes, and it must be the 2.15:1 reduction!

Or.... pick up a 270 transmission and a 270 Intermediate housing, and use your existing 250 lower gear unit.
But again, you must go through the shimming procedure if you use the 250 lower gear unit on the 270 Intermediate housing.


Bob said:
A 280 will hang on there quite nicely as well...
Yep..... as long as it's a 2.15:1 over-all reduction!
You must also match the female yoke splines to the AFT PDS splines.
(course spline vs fine spline)


If you go with a complete 270 or 280, the lower unit gears will be hypoid cut, instead of bevel cut.
No more gear whining.


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Picked up a 270 in good shape with a better PDS housing and extras out of Oregon City today for $400. :) Ill be back on the lake soon i hope!
 
it was one that came off a sbf shaft was even correct splines so no screwing with ujoints either. Got it all mounted up yesterday. Just need to rebuild the carb and maybe i can go catch some fish! Now i just need to wash off my hand prints :p118654779_350610156343722_102840933131802838_n.jpg
 
Make sure you have the correct lube in it !!!

Ditto!

30W Engine oil in cold water........ 40W Engine oil in warm waters like Florida for example.


it is motor oil like the good book says.
Previous AQ 250 had 90w in it from previous owner which i now know is incorrect. Maybe why she blew up

Heavy 90W gear oil will damage the slinger pump drive pin (one or two pins depending on the model).
When the slinger pump quits working, no cooler oil is pumped up to the transmission.
If that was the case, that may explain why the upper unit failed.


By the way, this is not uncommon. I've see many of the AQ series s/p drives with Merc gear oil in them.
Heavy gear oil is used in the AQ series Duo Prop only!




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