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Overdrive with no oil pressure - BN7 sideshift

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TimK

TimK

Jedi Knight
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After removing and replacing my transmission twice to install a new clutch and rear main oil seal, I took it out today for a drive and could not get the overdrive to work. It was working the last time I drove it (a year ago). I did Norman Nock's trouble shooting process and found the solenoid working fine. I then took off the oil pressure plug on the top right side of the overdrive and first turned the wheels by hand and got no pulsing of the oil. Then I started the engine and ran it in 2nd gear with no oil coming out the hole. The only thing I did to the OD was take out the brass drain plug, drain the oil and replace it with 30 weight motor oil. Any ideas why I now have no oil pressure and what I must do to fix it or further diagnose it?
 
After talking with David Nock I disassembled what I could while the transmission was in the car including the solenoid housing to expose the plug/spring/ball at the base of the oil pump. I removed the plug/spring/ball and cleaned everything I could reach. There was a lot of black sediment/sludge below the accumulator spring and housing which I cleaned out. I also took out the top plug/spring/ball and freed up the sliding part of the operating valve that is lifted by the solenoid lever arm. I got more free play and then reassembled everything. I adjusted the solenoid lifting arm to open the operating valve and started up the engine. I let it run in gear with the top plug loose. Eventually oil started coming out of the plug meaning that pressure was building. I then switched on the overdrive which resulted in the overdrive engaging. I was very pleased.

If anyone has any problems like this, I'd be happy to discuss further.
 
Hi Tim,
I have wondered where the access was to the ball and spring that go up against the side of the pump per the shop manual. On my BJ8 the solenoid mounts to a metal box that is attached to the side of the overdrive. The metal box has a cover that covers the operating arm.
So what you are saying is that if the solenoid and the adjustable arm that attaches to the cross shaft are removed, then you can remove the metal box and under the metal box you can access the ball and spring that go up against the side of the pump ? Is the access to the accumulator also under there ? I think you said that you can get it all apart when it is still in the car ?
I have to run Valvoline VR1 60w racing oil in my transmission because my overdrive didn't engage easily using MT90 when it was real hot, ( MT90 is close to 40w motor oil per Dave ). I know I must be making up for something wrong in my o/drive since it only works right with 60W motor oil. But Keoke and someone else on the forum did say that they have been using 60w VR1 in the summer and 50W in the winter for the last 20 years. I guess my overdrive either has some junk behind the accumulator or pump ball. Or I just have a worn pump or accumulator seal. Are you able to remove the accumulator from the o/d and replace the seal if necessary while the o/d is still installed in the car ?
Ed
 
Hi Ed,
There is a very in depth article on the Triumph overdrive here:
https://www.buckeyetriumphs.org/technical/AOD/AOD1/AOD1.htm
Multi sections.

It is the same as the AH unit.
Look at the Moss cat. here:
https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28884

There is a slight difference in the "solenoid bracket" solenoid mounting box. The early AH & the Triumph shown used the type 36 bracket. Later AH used the type 37 bracket.

Follow the instructions for gradually releasing the side cover/bracket to remove the pressure of the accumulator springs. Once the cover is off, the accumulator, the pump check valve, & the pump can be serviced with the OD in the car.
D
 
Not that Dave needs any confirmation from me, but I can confirm what he says based on my experience yesterday. I took out the accumulator spring and the accumulator tube, but I did not touch the accumulator piston. I didn't know how to grab it to pull it out and didn't know how I would get it back in. I also didn't know what purpose it would serve to remove it. The accumulator piston is used to build pressure. This pressure is released by the operating valve (basically a steel ball being lifted off its seat) opened by the solenoid activating which sends the pressure to the operating pistons. I don't know enough to know which of the parts would cause your problem. The operating pistons are not accessible without dismantling the overdrive outside of the car.

The tricky part was getting the ball back into the horizontal hole without dropping it -- which I did several times, thankfully not losing it. I used a magnet to get it to the hole opening and then pushed it in with a long bolt.

You do have to remove the solenoid and the lever arm to get the side cover/bracket off.

I checked out Dave's reference to the Triumph OD and it (the later OD model) looks just like mine. It is a very informative article.
 
Failure of the accumulator piston seal rings is a frequent cause of failure to build sufficient operating pressure. There are detailed directions on how to remove the accumulator piston if needed.
D
 
Thanks to both of you.
That article is excellent and helped me understand how everything works. As has been said before, these have to have enough pressure to work right. If there is not enough pressure, it is just a matter of finding out what is leaking. But it looks like there are a lot of places where it could potentially leak ! I guess for now I will run it the way it is since it seems to be working well when using the 60w VR1. At the first sign of any trouble, I'll pull off the solenoid can and check the one way valve/spring operation and also the accumulator seal. It is interesting that the part was redesigned and is now a little longer than the old one and has only one seal instead of two ?
I wonder if it was changed to simplify manufacturing or was it changed to correct a problem ???
The design of hard parts is not changed because of a whim.... So what Dave said about the accumulator leaking is probably right on target.
Ed
 
I just reread a Healey Club magazine article "Chatter March 1998" by Del Border that deals with removing the accumulator piston. It says to use a tool like a split ring pliers that provide opening force when squeezed rather than closing force. You can then just pull it out and check the hard durometer rubber seal ring. He also said you can used compressed air to blow it out. I could copy it and email it to you if you give me your email address.
 
The "Buckeye" Type A OD series was written by Nelson Riedel. It is the most accurate, detailed, well written information that I have found.

It was on the net for several years & then removed for some reason. Fortunately it is now back, for how long?.

During it's absence it could still be found here, although not totally complete. This site is very useful to track down old articles or those that have been removed from a site. "Waybackmachine"
https://www.archive.org/web/web.php

I would advise anyone who has this OD, or may need the information in the future, to download the articles NOW for safe keeping. You never know when a site is going to change.
D
 
There was also a Volvo site, look under flying brick... It was on my favorites two harddrives ago, but dunno now. It was very good also. Some volvo's used the J-type Laycock de Normanville o/d also.
 
TimK said:
After talking with David Nock I disassembled what I could while the transmission was in the car including the solenoid housing to expose the plug/spring/ball at the base of the oil pump. I removed the plug/spring/ball and cleaned everything I could reach. There was a lot of black sediment/sludge below the accumulator spring and housing which I cleaned out. I also took out the top plug/spring/ball and freed up the sliding part of the operating valve that is lifted by the solenoid lever arm. I got more free play and then reassembled everything. I adjusted the solenoid lifting arm to open the operating valve and started up the engine. I let it run in gear with the top plug loose. Eventually oil started coming out of the plug meaning that pressure was building. I then switched on the overdrive which resulted in the overdrive engaging. I was very pleased.

If anyone has any problems like this, I'd be happy to discuss further.
Click to expand...
I know this post is very old, but on the offhand that someone sees this, I'm having the EXACT same issue. Oil change, now no overdrive and no oil pressure. I've removed and cleaned the non-return valve at the base of the pump, cleaned the sludge from around the accumulator, cleaned the control valve and readjusted the solenoid. Still no oil pressure (no flow) at all from the hole at the top - nothing. It can't be the control valve, and I have a hard time believing that even if the accumulator was bad that I would not get any flow from the top plug. Seems to me it must be a problem at the pump, but why now? Is there a blockage, or can the pump stick so it does not move with the cam follower, thus isn't reciprocating? I don't know how a simple oil change could do this. Any help would be appreciated.
 
DLJ said:
I know this post is very old, but on the offhand that someone sees this, I'm having the EXACT same issue. Oil change, now no overdrive and no oil pressure. I've removed and cleaned the non-return valve at the base of the pump, cleaned the sludge from around the accumulator, cleaned the control valve and readjusted the solenoid. Still no oil pressure (no flow) at all from the hole at the top - nothing. It can't be the control valve, and I have a hard time believing that even if the accumulator was bad that I would not get any flow from the top plug. Seems to me it must be a problem at the pump, but why now? Is there a blockage, or can the pump stick so it does not move with the cam follower, thus isn't reciprocating? I don't know how a simple oil change could do this. Any help would be appreciated.
Click to expand...
You didn't mention if the solenoid is working.
 
Yes, working fine and adjusted. Tried to engage it manually as well. There is absolutely no oil pressure or flow to the operating valve when I remove the top plug.
 
Sorry I haven't figured out how to make a link to an old thread so here is a cut an paste of my overdrive troubles and what fixed them for me. Your mileage may vary. The end result was a fully functional OD in this case. It worked well for 15 years until I put in a Toyota 5 speed.

Jon, 7/13/23


From 2016
So the saga continues. When I first put the car on the road a few weeks ago I had no overdrive at all. I pulled the oil pump because I was getting no pressure. I found that the roller fork on the end of the pump piston was bent and the piston was sticking in the cylinder. It appeared that the piston/roller assembly had been installed by the previous person with the thick side of the fork against the steel pin that protrudes from the casing (I believe to prevent the piston from rotating, i.e. to keep the roller rolling on the cam rather than turning sideways). I happened to have a spare overdrive assembly, so I pulled the pump out of that. It looked pristine. Since installing that one I have been battling low pressure. I have found two things that are related that are probably causing my problem. Bear in mind that both overdrives were improperly assembled by folks unknown. One problem was that in addition to the bent piston, the ball bearing in the non-return check valve (of the spare pump I had) was the incorrect size. I'm not going to put it all back together until Monday, when I should get some new springs for the two ball bearing valves. Also after spending quite a bit of time with a magnifying glass looking at the ball seat in the pump body, I found that despite my lapping the seat(which is machined in the steel of the pump body) the seat looked like the craters of the moon, full of corrosion pits. I had put some fine valve grinding compound on a 5/16ths" ball bearing and spun it a few times. It looked OK using my reading glasses. Wrong. When I had it out this time I realized that it should have had a 1/4 " ball bearing and needed to be lapped properly. It took me 15 or 20 minutes of lapping with several ball bearings to get a seat that looked as it should. Staking the ball to the seat with a brass drift would have done nothing in this case. The latter was suggested in both articles I've read. So the pump is back in with the proper sized ball and a good seat. I'll let you all know what happens next week. Thanks for all of your suggestions.
 
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