Velvet Drive slipping in forward
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=51417
Printed Date: November-24-2024 at 7:24pm
Topic: Velvet Drive slipping in forward
Posted By: boatdawg
Subject: Velvet Drive slipping in forward
Date Posted: November-14-2023 at 8:20am
| I recently rebuilt a 71c transmission. Was working normally but was leaking from the input shaft seal. The input shaft was pitted. I had a machine shop put a sleeve on the part of the input shaft that the seal touches. I broke the transmission down enough to take the input shaft to the machine shop but did not do anything with the clutch packs/drum. When I reassembled, it would go into forward and reverse but it slips under load (going much more than idle speed). Using new oil. Oil level is good. No burned smell. Forward, N, and R pressure are all about 132 psi. I have the transmission back out and have it down to what I did to take the input shaft out and cannot see anything obvious. I'm thinking worn clutch packs but the transmission wasn't slipping until I "fixed" it. Would appreciate any input. Thank you. |
Replies:
Posted By: KENO
Date Posted: November-15-2023 at 7:17pm
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Quit fixin' what ain't broke Does it slip in Forward only or Forward and Reverse? What's a surgeon doing digging around inside an oily transmission?
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Posted By: 63 Skier
Date Posted: November-16-2023 at 5:39am
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They far more often slip in reverse than in forward as an early sign of problems. What oil did you use when you re-filled? ------------- '63 American Skier - '98 Sport Nautique |
Posted By: GottaSki
Date Posted: November-16-2023 at 8:33am
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And how much total hours on the transmission/clutch pack? ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: KENO
Date Posted: November-16-2023 at 9:16am
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Assuming it's only slipping in Forward like the title says, did you have the big convex forward clutch spring out and is there any chance you put it back in upside down, which would make forward clutch engagement kinda tough as compared to the spring being in right.
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Posted By: KENO
Date Posted: November-16-2023 at 9:45am
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The link below is a good disassembly video and you can continue on to part 2, the assembly video to double check what you may or may not have done  |
Posted By: boatdawg
Date Posted: November-20-2023 at 11:02am
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Appreciate everyone's help. I think I found the problem. I noticed the snap ring holding the forward piston in the drum was not in the groove. The forward piston had backed out of the drum just a fraction. The groove was exposed but not enough for the snap ring to fit. There was too much play/clearance in the clutch pack. I took out the forward clutch pack and several of the fiber disks looked worn. I replaced the whole forward clutch pack with bronze friction plates and new steel plates. Got the forward piston pressed into the drum and the snap ring in the groove. Rest of transmission cleaned and reassembled. Plan to pressure test tonight and check for leaks. Can't really test for slipping until I take the boat back to the lake. Will be back with an update after I test it. I use Dex III oil. Was only slipping in forward. The forward piston return spring was oriented properly. If I mess something up, I can just take it apart and try again which doesn't always work with surgery.
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Posted By: GottaSki
Date Posted: November-20-2023 at 11:22am
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Outstanding, sounds like you found it ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: 63 Skier
Date Posted: November-20-2023 at 11:23am
Good point! And, sounds like you are very good at taking it apart and re-assembling, which for me would be a bit of a challenge. Glad you found the likely cause. ------------- '63 American Skier - '98 Sport Nautique |
boatdawg wrote:Posted By: KENO
Date Posted: November-20-2023 at 1:07pm
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Good job Doc That snap ring would do it. The piston wouldn't be able to compress the spring and push the clutch plates together. Hope you made sure you got all the tools out before you closed her up
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Posted By: pjsmoreno
Date Posted: November-21-2023 at 9:07am
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I want to give thanks to Keno on giving that link on rebuilding
a velvet drive tranny. My boat has
always had that “Dirty Neutral” that drives me crazy ever since I brought her.
And I been hesitant to rebuilding and I didn’t want to send it out for I know I
can do it. I was taught to get your
hands dirty and learn as you go, and I’m still that way. I attempted rebuilding
an automotive transmission a long time ago on my first car and it didn’t go well.
I tried reading from transmission manuals on rebuilding but they don’t show and
tell you everything you will encounter along the way. And the tricks and tips
to boot. But that was before the internet and You Tube. I’m confident I can do
it now thanks to the videos. I have some major catching up to do so that
project probably won’t happen till next winter if all my other projects (other
than the boat) I have going on goes as plan. |