Overdrive Stops Working After Oil Change

[DLJ]

I recently drained and refilled the gearbox in my BT7, including the overdrive. Oil was pretty dirty, and since the car is a recent purchase, I'm thinking it might never have been changed. I put in Amsoil GL4 75W80 gearbox oil, supposedly close to SAE 30 engine oil in terms of viscosity and recommended (I thought). My OD worked perfectly prior to changing the oil, now it doesn't work. Relay and solenoid work, but not the OD. Looking for suggestions on what might be the problem.

 

[Bob_Spidell]

It's possible/likely just changing the oil dislodged something and clogged something in the hydraulic system's narrow passages (your choice of fluid is fine). I think, unless someone here has a better idea, you need to completely drain the gearbox and O/D, clean the O/D screen and fill it with some cheap 30W, take it for a short run and see if the O/D operates; maybe try this a couple times. If still no dice, try diesel oil or kerosene, but only do a static run (little/no shifting, etc.). If still no joy--you can try this a couple times--there's a couple other things you can try (get back to us). Worst case, you'll need a teardown of the O/D. Since the car is a recent purchase, and it looks like the DPO didn't maintain it properly, you'll likely find more things that need to be fixed (clutch, throwout bearing, etc.).

 

[DLJ]

Thanks for the information and for confirming that I have the right oil. I will drop it tomorrow and see how that goes. Hopefully it won’t have to come out.

 

[DLJ]

I dropped the oil and it was surprisingly dirty (after only about 15 miles), as well as there being more sludge around the magnet and screen. Nothing in the way of particles that I can see, but clearly the oil change 'cleaned' the transmission and stirred things up. I will get some 30 weight oil and see if that will flush it out but I have a nagging feeling that the OD will end up coming out. So much for my attempt at preventative maintenance.

 

[AUSMHLY]

Check to confirm you have oil pressure.
If the OD operating valve's small hole is blocked, no overdrive.
Flush with 30w non detergent, not regular 30w.
The way I flushed the tranny/OD was new Napa 30w non detergent (it's valvoline brand) oil. Drive about an hour and drain it. I used a nylon coffee filter basket as a strainer (10-20 microns I believe) for the oil and put it back in the tranny/OD. Did that multiple times till I didn't see any more Debis. Then new oil...30w non detergent.

 

[DLJ]

Thanks. Makes sense. My project this week.

 

[DLJ]

By the way. How do you check for oil pressure?

 

[Hamish Racing]

It should be an A type OD same as my triumph.
one issue given all you have done is change the oil is
There may not be enough oil in the box and od
As typically you fill the gearbox and the oil SLOWLY flows into the od. Thus you need to ensure the car is level and once the oil is in the gearbox leave it for 30min+ to allow the od to fill. Then top up the box again. Repeat until it takes no more oil.
Could just be low oil level.

 

[Bob_Spidell]

By the way. How do you check for oil pressure?

BJ8 Overdrive Oil Pressure

Hello, I'd like to check the oil pressure in my BJ8 transmission/overdrive. The work shop manual, Section G.9 Hydraulic Pressure, says: A working oil pressure of 470 to 490 lbs. per sq. in. (33.40 to 34.45 kg./cm.2) is required. The manual does not specify at what rpm or if that's in or out...

www.britishcarforum.com

 

[bighealeysource]

I would put in 30 or 40 weight non detergent and as suggested above, make sure you have the fluid level correct. If short on fluid will
not build up enough pressure to operate as that has happened to me in the past.

 

[nevets]

Check the archive posts on this forum. I recall some very good information regarding fixing a non-engaging OD from the late great Dave Russell. Check this post: > Overdrive Problem; Won't Engage <
Good luck!

 

[DLJ]

Yes. Fluid level isn’t the issue as I have checked it on the dipstick a few times, and per the manual, about 3.6 litres to fill it. It is interesting that everyone says no detergent. It would seem logical if I was not going to dump it soon, but since this is a flush, wouldn’t the detergent oil help flush out whatever is stuck?

 

[bighealeysource]

Sounds logical, just don't use it long term as bronze bits inside ( think they're bronze) don't like the detergent.

 

[Bob_Spidell]

Sounds logical, just don't use it long term as bronze bits inside ( think they're bronze) don't like the detergent.

Never heard that. However, there is some evidence the sulfur-based EP--or 'Extreme Pressure'--additives in GL-4/5 hypoid gear oils can affect brass and bronze components (they're added to protect the 'curvy' gears against the high shear forces in a hypoid gearset, and they're the reason GL-4/5 smells bad). Before switching to full-synthetic oil in all my gearboxes I ran 20W-50 engine ('detergent') oil in my BJ8 for tens of thousands of miles; on overhaul there was no evidence whatsoever of any detrimental effects.

I for one never bought the 'use non-detergent oil in gearboxes so all the particulates can coagulate and form a heavy sludge on the bottom of the box' theory. It appears we're seeing the result of sludge formation 'theory' in this thread. Note 30W 'non-detergent' was only spec'd in the early manuals; eventually BMC came to their senses.

 

[DLJ]

So I was on to other issues with my TR6 and am just getting back to the BT7 overdrive. Today I jacked the wheels off the ground, ran the car in 4th gear for several minutes and I'm not getting ANY flow out of the top of the operating valve (removed the bolt/plug from the top of the OD), so there's nothing at all coming from the pump, not even a pulse. Has anyone heard of these pumps possibly sticking in the down position so that the cam follower isn't riding on the cam, ie the pump isn't oscillating? That's all I can think of that would result in no 'action' from the pump. These things just aren't that complicated and I've checked everything else, the bottom line being there is no hydraulic pressure.

 

[John Turney]

With all the gunk you are getting from the Trans/OD, the pump could be stuck or the small passages plugged.

 

[AUSMHLY]

If I remember correctly (it's been a while) I believe when you remove the solenoid bracket (moss 37) and using a flashlight you can see if the oil pump plunger moves.

If you determine the OD pump is defective it can be removed. By removing the OD drain plug and using the correct tool (photo attached) or making one somewhat like it, you can pull the pump assembly straight down. Look for damage, fix or replace. No need to remove the transmission! (shout out to my Healey friend who turned me on to this and helped me with this)

For removal, you'll need to remove the overdrive ball valve (moss 101) plunger (moss 102) spring (moss103) copper washer (moss104) and screw plug (moss 105) first.

The ball valve and plunger maybe worn and not making a seal. Some suggest replacement or next step possibly lapping where the ball valve contacts.

Knowable guys here and we'll help you.
Good luck

 

[AUSMHLY]

Today I jacked the wheels off the ground, ran the car in 4th gear for several minutes and I'm not getting ANY flow out of the top of the operating valve (removed the bolt/plug from the top of the OD), so there's nothing at all coming from the pump, not even a pulse.

As John pointed out, the passages could be plugged. One passage is the operating valve.
It has a pin hole, blowing through it will confirm it is plugged or not.

 

[DLJ]

If I remember correctly (it's been a while) I believe when you remove the solenoid bracket (moss 37) and using a flashlight you can see if the oil pump plunger moves.

If you determine the OD pump is defective it can be removed. By removing the OD drain plug and using the correct tool (photo attached) or making one somewhat like it, you can pull the pump assembly straight down. Look for damage, fix or replace. No need to remove the transmission! (shout out to my Healey friend who turned me on to this and helped me with this)

For removal, you'll need to remove the overdrive ball valve (moss 101) plunger (moss 102) spring (moss103) copper washer (moss104) and screw plug (moss 105) first.

The ball valve and plunger maybe worn and not making a seal. Some suggest replacement or next step possibly lapping where the ball valve contacts.

Knowable guys here and we'll help you.
Good luck

Thanks for the advice. I had the ball valve assembly out already but didn't check the pump action when I was there. I beleive you are right that you may be able to see the pump plunger move if you take out the ball valve. I also wonder if you can remove the plug at the base of the pump and by turning the driveshaft, see if the plunger moves. Do you think it is very likely that the pump or the ball valve just 'went bad' all of a sudden? The OD worked perfectly prior to changing the oil, and that's what makes me think the pump could somehow be stuck (or there's no oil getting to the pump). Does the cam follower and return spring come out through the bottom with the pump? I'm worried it won't and then I'll have to take the OD apart.

 

[AUSMHLY]

Disclaimer, I'm a learn as I go. With the help of the smarter guys here I'm becoming more hands on. More seasoned guys please jump.

1st I'd check the pin hole in the operating valve to see if it's plugged. Wouldn't that be fantastic if that was the root of the problem.
2nd I'd continue to flush the system until no debris shows up and the oil is clear and clean. (Even if it doesn't fix the problem, what's the down side to having debris free clean fluid.)

Food for thought. I believe the 3 types of oil we use are 20w-50 motor oil (which is a detergent), 30w non detergent and Redline MT?
I used 30w over and over for the flush because I thought it was the correct oil per recommendation of Healey Surgeons web site and phone call to Bruce. From their website:
Fill the transmission with 30 weight NON DETERGENT oil. If this isn’t available at your local auto parts store, machine shops will carry it. Or we can supply it. Change oil after an initial test drive and has gotten good and hot.. It will need 3.75 quarts for sideshift and 2.75 quarts for centershift

BCS has an orange Austin-Healey Tech Talk Technical Article Book (I use all the time and recommend) that states on page 23, 20w-50w is satisfactory or to be correct, 30w non-detergent. (photo attached of that from the book). HOWEVER, I believe David Nock of BCS now recommends Redline.

My point for your situation is flushing the system with 20w-50 seems logical because of the detergent. Healey's have been using it for a very long time with no issues.

I also wonder if you can remove the plug at the base of the pump and by turning the driveshaft, see if the plunger moves.
Sorry, no. You'll see the bottom of the oil pump body (moss 97)

Do you think it is very likely that the pump or the ball valve just 'went bad' all of a sudden?
Seasoned guys, please field this one.

Does the cam follower and return spring come out through the bottom with the pump?
Cam follower aka oil pump cam (moss 92) is slid on the main shaft, and held in place when the the OD and Transmission are pressed together.
Return spring (moss 96) is part of the oil pump plunger and will come out with the unit from the bottom of the OD.

I'm worried it won't and then I'll have to take the OD apart.
If it come so that, feel free to PM me. I've had the tranny/od out many times and there are some some things that make it easier once you know how. You don't need to take the OD apart, just remove it from the transmission. Removing the adaptor plate (moss 11) from the transmission is the best easiest way. Then you'll be able to see if there is any damage to the pump or cam and confirm pump moves. Putting OD back on, well it's heavy and you need the mainshaft spline to line up with the OD spline. Then use the string procedure to keep the oil pump plunger roller down so the mainshaft will not contact it allowing the shaft to enter the OD.

Hopefully flushing the fluid will dislodge any debris, gunk or stuck parts.
You may look into the accumulator housing assembly.

Best of luck.