Another OD question

[nevets]

Thanks agin for the info. Since the OD and gearbox share the same oil, I assume that draining the gearbox oil is all that is necessary to drain the OD. The big nut mentioned earlier, which gives access to the screen and which looks like it requires a special wrench, is not a drill port?

 

[Keoke]

Thanks agin for the info. Since the OD and gearbox share the same oil, I assume that draining the gearbox oil is all that is necessary to drain the OD. The big nut mentioned earlier, which gives access to the screen and which looks like it requires a special wrench, is not a drill port?

Yes that is correct:
"
A soft drift or block of wood may be used to loosen the nut, however , do not hammer on it directly with a metal hammer.

 

[Bob_Spidell]

Thanks agin for the info. Since the OD and gearbox share the same oil, I assume that draining the gearbox oil is all that is necessary to drain the OD. The big nut mentioned earlier, which gives access to the screen and which looks like it requires a special wrench, is not a drill port?

Yes, a 'special' tool is required. Several vendors sell a couple different versions. Not sure what you mean by 'drill port,' but you wouldn't want to do any drilling on an OD.

I think draining the gearbox will get most, but not all of the oil. Besides, you need to check the screen for metal or sludge and clean it. For a BJ8, there are 3 circular, rubberized magnets that go under the screen; make sure you have those.

 

[John Turney]

The big nut is a drain port, in addition to the one on the transmission. Yes, it takes a special tool. I made one by welding a couple lengths of 1/4" square steel to a 1/8" x 2" steel plate. The pieces of 1/4" square steel fit in opposite cutouts in the big nut.

 

[nevets]

I meant drain port, not drill port. I don't weld, so maybe some love taps with a block of wood as Keoke suggested. Thanks again guys.

 

[BruceAllcorn]

Okay, here is where I am. First, I drained the "old" Redline MT-90 oil and replaced it with non-detergent 30 wt motor oil to see if that would make any difference. It made no difference. Then I replaced the acculator pressure spring. The new one was about 1/4" longer than the one I was replacing. By then I had put the car up on blocks to run it. I ran it with the new spring installed and it wouldn't switch into overdrive at all. I then checked the pressure at the operating valve. The pressure would get up to about 400 psi at about 2000 rpm and would drop down as low as about 200 psi as I reduced rpm's. When I shut the car off the pressure would drop to 0 psi. I have since removed the operating valve parts and the pump valve parts and inspected the springs and ball bearings and didn't see anything that looked unusual. I also turned the drive shaft with the car in neutral to confirm that the plunger was operating, and it was, with about 1/4"-3/8" movement. I was going to remove the oil pump itself but I haven't quite decided how to do that yet since I don't have an extraction tool. Anyone know where they might be available? I've seen a picture, so I know the principle- maybe I can make something. For those of you that know a whole lot more about these overdrives than I do, what would be your next step?

 

[Bob_Spidell]

I had no luck, so I had David Nock mate my OD to my gearbox last year. He removed the pump; for inspection and to make mating the units easier. His mechanic screwed a couple of long (3+") screws of the proper thread into the two holes and used some sort of puller--sorry, don't remember the exact tool (think I might not have been watching)--to extract the pump (I think you might make do with a small slide puller somehow).

When I replaced my accumulator with a DWR 'uprated' unit, I noticed that the walls of the old cylinder were somewhat scored--the piston has metal rings--and this could result in a loss of pressure, so you might have to replace the whole unit. My pump was OK, with over 200K miles, and they're bathed in oil so as long as no grit gets to them they should last. My guess would be either your accumulator cylinder is scored, or the ball check-valve on the pump isn't seating well. It sounds like your pump can produce sufficient pressure, but something is relieving it when RPMs drop. Best guess is the check valve.

So, you were able to get the accumulator piston out without pulling the OD? I may have to do this as well, as the new O-rings I installed appear to be leaking.

Side note: don't get me wrong, Moss is a great company for us owners, but the last few seals and O-rings I've bought from them have been 'close but no cigar.' Probably, exact replacements--like for steering box shaft seals--are NLA, so they stock the closest thing they can get. Unfortunately, there is no such thing as 'close enough' with seals and O-rings. I replaced the operating shaft O-rings and, sure enough, at least the outside one is leaking. The following is by Roger Moment--acknowledged Healey guru--and found in the latest Austin-Healey Magazine:



I bought some of these--ordering was, uh, a 'challenge'--so send me your address in a PM and I'll mail you a couple if you like.

Edit: One other thing occurred to me: The two pistons that push the OD cone clutch into the brake ring have rings as well; I believe older cars use metal ones, and newer ones have O-rings, but I think they're only in play when you engage the OD, but might bleed down too fast if the rings/O-rings are worn or their cylinders are scored.

 

[roscoe]

You said you pulled the "pump valve" parts; I assume you mean the pressure relief cap, spring and ball bearing. I ask because you exhibit the exact same issues I dealt with. Did you look at the seat for the ball bearing closely? Were you able to measure the ball bearing in several directions to check for out of round conditions. The ball bearing in mine looked good at first inspection but turned out to be very worn when measured and , yes, on second look you could see it. It doesn't take much to bleed off the oil pressure. As one comment above mentioned staking the ball to the seat with a mallet I should point out that this did nothing for me. When you think about what you are doing when you stake a ball to a seat, it might improve things for a while, but lapping has got to be better than smashing. What changed everything was seeing the extensive pitting on the seat and lapping that until it was smooth with a new ball bearing and then installing fresh ball bearing. There can be other causes but this is relatively easy to check and fix.

 

[Healey Nut]

Just because the pump generates the pressure that doesnt guarantee the OD will engage . The amount of lift of the OD valve by the solenoid is critical and that whole explanation in the manual about using a drill bit to the align with the hole in the side of the OD doesnt work .
If you go onto the Healey 6 website theres a whole slew of information about ODs and how to set them up correctly and fix them . The little ball under the operating valve rod has to lift if my memory is correct 5/64ths “ which you can measure with a depth caliper .
I rebuilt both my ODs for my BJ8s and set them using the info off the Healey 6 site and they work perfectly .
I cant help but note that you never mention wether you checked to OD screen filter or if you drained to OD at all .
If you didnt do this you not doing the whole job and you cant determine the problem if you dont do the basics .

 

[Healey Nut]

https://www.britishcarforum.com/bcf/showthread.php?101793-Overdrive-working-but-not-really-working

check this thread , links on post #9 .
All will be revealed .

 

[BruceAllcorn]

Thanks to all, great info. I've got some studying to do. Bob, I was able to remove the accumulator spring by taking out the front top stud that helps to hold the solenoid bracket on to the overdrive. Before I backed off on the 2 screws to relieve the pressure on the accumulator spring I took the two nuts from the studs and put them on the top stud (the longer one) back to back and then backed that stud out. Without doing that I would not have had enough room between the solenoid bracket and frame to get the bracket off.

And to clarify, I actually drained the whole unit, filled it up and ran it a few miles to "flush", and drained the unit the 2nd time. The strainer was clean both times, but the plug did not have the magnets which I ordered and installed after the first drain. When I drained it the first time there was some "sludge", especially in the area uncovered by removing the solenoid bracket. I cleaned all that out prior to filling the unit back up, driving, and then draining again.

I'll check the items mentioned above and report back. I have got a line on a rebuilt OD within about 200 miles of where I live, and a line on a fellow who can rebuild mine as recommended by Allen Hendrix, but I'd obviously like to find a fix without having to go that far. Thanks again to everybody!

 

[Bob_Spidell]

While we're on the topic: If your OD leaks into the (sealed) solenoid box, conceivably, if enough oil gets in there, your solenoid could 'hydro-lock' and possibly be unable to en/disengage the OD. Otherwise, besides being messy and causing the OD oil level to drop this wouldn't be an issue if the lost oil was allowed to drain. Anyone considered drilling a small hole in the bottom of the solenoid box--at the lowest point would be best--so oil could drain, and maybe putting a cotter in there to prevent clogs (like the hole in the bell housing)? Note earlier ODs had the solenoid exposed to the elements (i.e. no box).

 

[BruceAllcorn]

Thanks to Healey Nut for the info provided in your post of 02-08-19, 7:36 PM (above). For those who didn't "check it out", click on the thread provided and then go down to the 10th post, also by Healey Nut on 06-25-2015, 11:40 PM and click on that thread. It is a 3-part series on the OD and I have found it to be very helpful. In fact, I'm now convinced that my problem started with not having the solenoid switching mechanism set up right and it provides an excellent way to do that and to remove the accumulator piston-I used the air method as it was much easier with the OD unit still in the car. My piston and rings still appeared to be in good shape, but since I had it out I decided to get the upgraded model from AH Spares along with new springs, etc. for the operating valve and non-return valve at the pump and including the copper washer for the operating valve that is NA at Moss. At some point a previous owner had used a washer that was too large of a diameter, which actually raised the plug on the operating valve up by at least 1/32", which I think was also part of the problem. Ordered the parts yesterday and they are due tomorrow! I will follow up here when I have re-assembled everything and checked it out.