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Up-date on BN2 overdrive problem

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bighealeysource

bighealeysource

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Update on BN2 overdrive problem

Hey all,
I had a thread in here a couple of months ago about how my overdrive would work beautifully when first starting out but once fully warmed up after 20+ minutes, would no longer engage or would simply disengage. It was rebuilt by Healey Surgeons and worked fine on the bench test but obviously Bruce could not test it in the car as I shipped it to him from SC. I have tried everything to get this problem resolved and appreciate a lot of help from Andrea, our Italian poster and Healey owner, in trying to walk me through this issue. Here is what I have tired-

* replaced ball bearings and springs on both operating valve and pump valve
* started off using 30 wt non detergent oil, now using 40 wt non detergent

Many of you have seen the excellent articles on trouble shooting the A type overdrive from Buckeye Triumph club - have followed their recommendations and added washers to the
accumulator spring ( have later smaller one) to increase operating pressure as main issue was lack of operating pressure in trouble shooting article.With old spring and two washers got it up to 400 pounds. Decided to purchase a new spring from Moss who sources it from AH Spares in UK. Using a 600 pound pressure gauge with adapter screwed into operating valve plug hole.

* two washers and new spring resulted in the pressure going past 600 pound mark so shut it down and took apart again
* no washers and new spring gave me 490 - 500 pounds but problem of going out of overdrive after fully warm still did not stop
* added one washer and pressure got up to 550 pounds and OD again works perfect when cold but once fully warmed up but now maybe 30 minutes, OD stops working. Know 550 pounds is on high side but pressure drops off perfectly when OD engaged and comes right back up. Works perfect until heated up.

All electrics have been replaced including solenoid, gear switch and relay. If I stop when problem occurs and shut down engine, can hear solenoid activating so electrics still working when hot.

This problem has me and others stumped. Anyone have any other ideas ?????

Thanks,
Mike
 
Re: Update on BN2 overdrive problem

You didn't mention how low the pressure dropped when it got hot. I had a very peculiar problem when I completed my BN2 rebuild that turned out to be low OD oil pump pressure that was caused by pitting where the pump relief valve ball bearing seats, preventing the relief valve from ever closing fully and allowing full pressure to build. I (after weeks of head scratching) ended up dressing the seat for the ball bearing and much to my amazement (and a new ball bearing because the one that was in there actually was no longer a sphere) the pressure came back up and it has worked flawlessly for several years. I was literally at the end of my rope for ideas, and I wish I had a video of my "end zone" dance when that overdrive started working. I would imagine that oil temperature could have an effect on a scenario like this.
 
Re: Update on BN2 overdrive problem

Mike,
Sorry to hear that OD is still not cooperating. Hope that won't cause a problem with getting up here for the big event at Patriots Point on June 27th. You have special parking for your former Great Race car!

Irene
 
Re: Update on BN2 overdrive problem

Hey Roscoe,
I'll have to pull the trans tunnel off and reinstall the pressure gauge to see what the pressure is falling off to when fully hot but at this stage, certainly worth the effort. Besides, I am getting real quick on taking the seats out, carpets, and tunnel to check this stuff out. I'll address the seat for the ball bearing as that had been recommended as well to make sure it was perfect. As I said, pressure dropped down immediately upon engaging the OD when out road testing with the drive shaft and ground staring at you as you drive down your local testing highway but then came right back up. But did not run around for the 20 or 30 minutes like that as would have melted by then. Will just have to put on my flame and heat resistant clothing to try it now - just kidding,wish I had some - and see what happens.
Thanks,
Mike

PS - Hey Irene - I'll be up there at Patriot's Point as can cruise on up hwy 17 without OD if need be as fine at 50 to 60 mph - see you there !!!!
 
Re: Update on BN2 overdrive problem

Some folks will cringe but I cut my tunnel in half so I can take out the forward section without removing the aft part. I did this around the same time I was doing what you are and it just makes getting to that part of the car way easier. Pull the carpet back and take out some screws and voila, you can get to all the important stuff easily.
 
Re: Update on BN2 overdrive problem

Hey Roscoe,
I have thought of doing exactly that or something close to it. Worse part is the forward section as I do not remove the steering wheel when I take it off or go to reinstall. Have thought about cutting access ports which would allow me to get to the operating lever on the right side and the operating valve on the top of the OD. However, have become very quick in taking the seats out, removing the carpets and then pulling the tunnel off. Can pull it all off in about 15 minutes tops so guess for now I will keep the wrath of the Healey gods off by not making any of those changes to the tunnel. But boy, sure would be easy !!!
Thanks,
Mike
 
Re: Update on BN2 overdrive problem

Serviceability apparently wasn't a big issue in the design of some of the BMC sports cars. Most Spridget restorers have had to deal with an access hole torched in the floorpan so the mechanic could easily get to the front u-joint. I remember walking into my friend's shop when he was working on an E-type. Bonnet was off and engine was on a hoist. "Whatcha doing?", i asked. "Clutch job." :nightmare:
 
Re: Update on BN2 overdrive problem

UPDATE - Well, the Healey gods have finally taken pity on me and my overdrive. The last thing I could do before looking into replacing the oil pump - and Bruce Phillips has only replaced like one in all his years of rebuilding overdrives - was to go back to the ball bearing for the oil pump valve and make sure it was seated properly. Got a $4 brass drift from Amazon, took the trans tunnel off and side cover to gain access to the oil pump valve, took out the plunger, spring and the ball bearing, put the ball bearing back in ( which about requires you to have 3 hands to get the ball bearing in and not roll back out), SEATED it very carefully using the brass drift, put it all back together and viola, IT WORKS even when hot !!! So for anyone doing work on their overdrive, make sure to SEAT that ball bearing. Some have suggested also seating the ball bearing on the operating valve on top of the OD case but working fine now. If I have to remove the tunnel for something down the road will probably do that but for now, it is staying on.
Regards
Mike
 
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