DP290A guru's needed - leaking input shaft seals

[Fun Times]

Re: DP290A guru's needed - leaking input shaft seals

I think that as soon as the bolt is loosened that changes the tension on the sleeve.

Just like to add for reference to other forum members that may read this, The quote above is how I was taught to treat this bolt, anytime it has been loosened/backed off it needs a new crush sleeve.

Scott I'm happy to see your going to try a new crush sleeve even if it may not make much sense visually to do it. Jugging by your many posts of excellent advice given, I know your a man of wanting things right even if it may not make total sense at the moment. It may not even be the problem but at least you know your doing everything within your power for it to be done correctly to the best of your knowledge.

 

[Scott Danforth]

Re: DP290A guru's needed - leaking input shaft seals

sorry to disappoint people. even after replacing the seals and crush sleave with new crush sleeve and seals, the drive is still leaking. finished up the gearbox prior to my Abu Dhabi trip. took it out this past weekend. was late on Saturday, so finally got a chance to check tonight. oil level low, and about 10 ounces of oil in the bellows area

the design of the double bearing box is quite simple. the crush sleeve sets the initial spacing between the two bearing cones. the races are in the housing, and located by the housing. the gear and thrust washer come together to capture both outside ends of the cones.


Followed the procedure in the manual. bearing pre-torque is at 2.2#

upon reassembly of the drive, pressure tested to 18 psi for 24 hours.

note that the torque on the bolt securing the shaft to the gear cannot affect the crush of the sleeve unless the gear is compressed, which cannot happen with the fastener used. the torque can, however not be proper for the fastener and could lead to the fastener coming loose. however in this case, loctite and a torque wrence are your friends

That being stated the next step is to buy new bearings. from there, I will replace the bearings and races (which is a total waste of perfectly good bearings. I will then replace the seals again.

If this does not cure the leak, I will consider det chord or a road flare in the fuel tank.

 

[Scott Danforth]

I found a good sized nick in the input shaft seal, my assumption is from the shoulder washer catching the lip upon my last assembly

If anyone needs the bearing part numbers for the double bearing box:

SKF 30207 J2/Q Qty 1
SKF 31307 J2/Q Qty 1

Also, on the 75mm x 45mm x 8mm input shaft seal , the original seal is an SKF 692515 (45x75x8 HMS5 RG) http://www.skf.com/us/products/seal...pt/index.html?prodid=704601279&imperial=false

However my last seals from Volvo are Stefa’s

I wish I would have known the actual seal numbers prior. $7 is much less than $26

 

[muc]

~~Sounds like you found the leak --- great.
But I don'€™t agree with your comment.

"€œnote that the torque on the bolt securing the shaft to the gear cannot affect the crush of the sleeve unless the gear is compressed, which cannot happen with the fastener used. the torque can, however not be proper for the fastener and could lead to the fastener coming loose. however in this case, loctite and a torque wrence are your friends"

The bolt is what crushes the crush sleeve --- that is what sets the preload on the bearings.
You do NOT use a torque wrench on this bolt (unless you want to use an inch pound dial type torque wrench for the rolling torque instead of the spring scale and string that the manual calls for) I do however use Loctite and the Loctite primer / activator on that bolt.

 

[Scott Danforth]

Muc, I would agree on one condition. you prove to me something different than I observed, and my years of engineering taught me. The only way that you coiuld be right is something needs to not be clamped, or the bearing pressed on the gear needs to not be on the shoulder of the gear and it needs to be floating. Which, if it floats, the thrust vector of the gear in mesh would move the gear further into the bearing and change the preload.

answer these questions and make your own conclusion

Is the larger bearing that supports the back side of the gear installed up to the shoulder of the gear?
is the thrust washer to gear joint to be a clamped joint, or is the thrust washer allowed to move with respect of the gear and drive yoke?
if it is allowed to move, it would cause a leak path since the o-ring would not be compressed
since it is intended to be a clamped joint between the shoulder washer, gear stub, and the yoke. once these surfaces are brought together, how much force will it take to make the shoulder washer move with respect to the gear, therefore adding additional preload?

since the bearing is installed to the shoulder of the gear, the joint between the thust washer, gear and yoke is a clamped joint, and additional force to change the dimensions would have to crush the gear. what would your conclusion be

I used a digital inline scale and string like the manual states.

 

[muc]

~~I think I see where you are mistaken.
The thrust washer doesn't push against the gear, it pushes against the bearing. That bearing is free to float on the gear.
Maybe the best way to try and explain this is --- it'™s called a crush sleeve because it crushes during installation.

 

[Scott Danforth]

Muc, lower left corner on page 36 (step 6) of the manual indicates that the bolt is to be torqued to 55 lb-ft of torque. this will crush the sleeve, mash the bearings and take any gap between the washer and gear.

it also says to add or remove shims between the gear and washer to get the desired pre-torque (prestressing).

again, indicating that the crush sleeve is there only to set the gap between the two bearing cones and the pre-torque comes from shimming.

 

[muc]

~~Now I see what’s going on.
You’re in the wrong part of the manual.
The instructions your using is for an earlier model. You have a 290A. Those instructions begin on page 46.
No shims in a 290A and no crush sleeve in a 290.
Made the same mistake myself years ago.

 

[Scott Danforth]

then I have another issue. the max pre-load I can get is 2.2#. the shoulder washer and the gear is solid (no float) and that is with new bearings.

short of pulling the gear, machining the length shorter, or machining the recess deeper in the washer, I'm bottomed out on the preload.

I could shim between the gear and large bearing, however that would really mess up my contact area

 

[muc]

The only way you would need to machine or shim is if there are some wrong parts in there.
If you want to be sure --- remove the crush sleeve and tighten the bolt, if preload goes way up with out the crush sleeve in it, than you know that your just not tightening the bolt enough.
I use a 1/2" ratchet to tighten that boat and have to pull on it pretty hard. Probably putting over 70 ft lbs of torque to it.

 

[Scott Danforth]

already thought of that. it didnt change the pre-load. cant be any wrong parts. I put the old washer back in just to check, and the same issue. the washer bottoms out on the gear just as the preload hits the very bottom of the range.

 

[muc]

Maybe the the aftermarket bearings you bought in post #29 are the wrong size? Maybe the big bearing isn't pressed all the way onto the gear?

 

[Scott Danforth]

muc, since the original bearings are SKF, and the new bearings are SKF, I dont think it is that. Remember, VP doesnt make the bearings, they buy them. Both the old and new bearings mic the same for assembly height (within 0.001"). by nature of the gear box design, the big bearing needs to be pressed onto the gear fully. if I didnt press it on fully, I could get a higher preload, however it would loosen up over time due to the pressure angle of the gearset.

I think that the manufacturing tolerance stackup on all the machined parts is just that close to only allow hitting the minimum preload. IE, the gear stub is on the high side of the tolerance, the bores in the casting at the low side of the tolerance. I made a 0.004" shim, and it brought my preload up to where it should be

 

[RickyGee]

Hey Scott, did you get the oil leak fixed? I'm well underway with the PDS bearing changes on my barge and one of the drives had a couple cups of drive oil in the boot. Was it the nick in the seal? BTW, thanks for the SKF numbers. -Rick

 

[Scott Danforth]

99% certain it was the nick in the seal. 1% unsure if it was the replacement bearings. in either event, replace the front seal and the sealing/shoulder washer.