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Velvet Drive 72c shifting problem |
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blammie 
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 Topic: Velvet Drive 72c shifting problemPosted: April-27-2022 at 11:36am |
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Picked up another 60s CC last fall. Boat was a good gamble as the motor runs well and it's on a nice trailer. Looking for some advice on a Borg Warner 71c though. Tested with motor running last year. It is stuck in neutral and will not shift. Linkage moves but valve doesn't seem to engage. I'm looking to educate myself, and make this thing run. What is the best way to assess whether the pump is actually functioning properly? I'm thinking my culprit is either the pump or the selector valve. I'm willing to tear it down for an inspection and rebuild if necessary, but I've never been in one of these, and not trying to move to fast. One step at a time. I'd like to first diagnose the apparent problem and regroup from there. I've been doing some research and looked through the service manual as well as watched a couple vids , but any advice on getting started would be appreciated. Specifically, it seems that the pump might not be developing pressure. How do I verify this? And is the resolution for a bad pump just seals, or does one replace the whole unit? Thanks on advance.
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 10831 |
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Posted: April-27-2022 at 2:04pm |
Here's a picture of an old 71C on a test rig. The gauge in the back is in the main pressure test port. The port has a 3/8 NPT pipe plug screwed into it. It may come out easy or may come out real hard, most likely real hard if it's never been out. You need a test gauge that goes to at least 200 psi and your choice of adapters/couplings/bushings to be able to screw things into the test port. You don't have to unhook anything else from the transmission, just screw the test rig in and then start the engine You should see about 135 ish psi with the engine in neutral at idle speed. If you see nothing or a lot less than 135ish you'll have choices as to what the problem could be. One choice that everybody in this situation hopes for is that the control valve is bad, since it can be removed pretty easily with the transmission in the boat. you can hope, but chances of it being bad are pretty slim Another choice would be the damper plate on the flywheel is shot. That's usually accompanied by loud metallic grinding noises. And then there's the bad pump choice. That's a good start to see if you have normal operating pressure before tearing into anything, If all was well with the transmission, when you shift to Forward the same gauge will still read the same 135 ish and if the gauge was screwed into the reverse test port at the top front of the transmission in the picture, when you shift to reverse. it will read the same 135ish and in neutral it will read zero. That test port is 1/4 NPT threads and the typical gauge will screw right in. So, check the main port pressure to start and post the results
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3654 |
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Posted: April-27-2022 at 3:05pm |
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Ken’s information above is about as good as you will find anywhere. You should be able to quickly determine what you are up against.
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21145 |
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Posted: April-27-2022 at 6:26pm |
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Per my response on fb, I’m still betting on wrong pump indexing = no pressure.
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KENO
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Posted: April-28-2022 at 7:40am |
I guess that would fall right into the bad pump (but easy to fix) category Since the engine rotation hasn't been mentioned here, you could look at the pictures below and if you have zero pressure, make sure it's indexed the right way. All of the pictures have to be rotated 90 degrees to the right First picture is a pump indexed for reverse rotation  Second picture is a pump indexed for normal rotation  This last picture is also an older style pump (like yours might be since the boat is from the 60's) indexed for Normal Rotation. You'll see a RH after the arrow. You might say that the RH and LH is there strictly to confuse people and make them index the pump wrong thinking that if they have a RH (reverse rotation) engine that the RH should be at the top. It confused enough people that Borg Warner eventually deleted the RH and LH stampings The best thing you can do is pay attention to the arrow and just plain totally ignore the RH and LH stampings. The least confusing way to index your pump is to look at your engine and figure out which way it rotates and then index the pump so that the arrow after the word TOP is pointing the same way as the engine rotates...........and you can't go wrong  |
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KENO
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Posted: April-28-2022 at 11:11am |
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If you want to read the same pump indexing stuff in an old Borg Warner manual, click on the link below
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blammie
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Posted: May-01-2022 at 2:49pm |
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Thank you gentlemen. The info was very helpful. So this is where I'm at. I got it started today. I can verify I have oil moving when looking in dipstick hole. This seemed good thing until I checked the pressure. Thanks for the info Keno. I was able to get the reverse plug loose, and have no pressure at the reverse port. I should be looking for pressure not vacuum, correct? The forward one (rear) is tight, and I havent gotten it loose yet. Can I use heat? I'll get that out and verify pressure, but it doesn't look good. What's my next step? Control Valve? I appreciate the help gentlemen.
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KENO
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Posted: May-01-2022 at 5:43pm |
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Well.....it sure seems like your pump is at least moving some oil and isn't indexed wrong because it would move no oil if it was wrong.
Just to be sure we're on the same page, if you have the gauge hooked to the reverse test port, you'll have zero pressure in neutral and when you shift to reverse the pressure should go up to the 135ish mentioned earlier. Check that if you haven't already Then, I'd be pulling the control valve out and looking for anything obvious like a broken spring or a valve that just sorta "fell apart". It doesn't take long and you've got nothing to lose by doing it. And.............good luck PS heat is your friend with that test plug
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KENO
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Posted: May-02-2022 at 10:16am |
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Now for some "not so good" news Brett
If the pump is indexed wrong you'll still see what looks like flow in the sump but it's just oil being moved around by the rotating parts that rotate with the input shaft I checked this out this morning on my little test rig in the second post in this thread. So there's still a really good chance your pump is indexed wrong 
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blammie
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Posted: May-07-2022 at 8:23am |
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Going to get back into this after a graduation this morning. The plan is to open that rear test plug and check pressure. I already know I have zero at the front plug. My question is this. If I verify no pressure at reverse plug, what is my next step? I have a spare, known working 71c. Do I swap a good valve in to rule that in or out, or should I just swap the spare trans in. Obviously (I think), if I have pressure at the rear, I will swap the valves and test. My goal is two working transmissions. Thanks
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KENO
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Posted: May-07-2022 at 8:54am |
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Assuming that you get no pressure at the main test port, swapping the control valves is relatively easy. Just don't lose the spring loaded detent ball behind the shift lever, when taking the lever off or when reassembling  Have you verified zero pressure in Reverse like in the quote below, if you have, I wouldn't worry about getting the main test port plug out and just move on to swap control valves
Then after all that, you'll probably end up pulling the transmission to reindex the pump or just swap transmissions, but there's some hope still that it's a control valve issue.
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blammie
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Posted: May-07-2022 at 4:33pm |
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Swapped the control valve today, and nothing. Looks like I'm swapping transmissions for now. You can expect more questions on that trans this summer, but for now I'm just trying to make it in the water. Any advice on tranny fluid? Figure an oil change is appropriate before a swap. Seems like Dextron is what is recommended these days. I have a few quarts left from a Jag I owned. Their sites description says: "TITAN ATF 4000 is suitable for multi-purpose applications, reliable up to high loads and is recommended when Automatic Transmission Fluids DEXRON III are specified. In GM-Applications backward compatibility to older DEXRON- specifications is granted." Seems like it should work. Any other pitfalls I should be careful to avoid? I appreciate your advice, thanks.
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TRBenj wrote: