Flushing the Transmission/Overdrive

[AUSMHLY]

Just finished rebuilding the BJ8 transmission. The internal transmission case and all parts are clean. The OD was working, so I didn't open it up. Now that the tranny/od are installed I found I the OD wasn't working. So I'm going to R&R the oil pump to make sure it's in correctly.

When I drained the oil, I see a lot of small particles/debris, some looks like old gray RTV. I used Hylomar when I put the new gaskets on, so it's not from me. I'm assuming the debris is coming from the OD.

Is there a way to flush the tranny/OD and if so, what is the product and procedure?

Starting with an empty tranny/OD, would a ATF or kerosene, run for 5 minutes, drain, be safe and do the job?
If so, do I need to the same amount as required for an oil change, or will 2 quarts be enough for a flush?

Thank you in advance.

 

[Bob_Spidell]

My take (I'll send you a bill ): First, find out why your O/D quit working; diagnostics, guesses, tips, tricks, etc. abound on this forum and others. If you didn't tear down the O/D the oil pump would not have been touched--it's bolted in--except to get its roller out of the way. My best guess is the collar on the gearbox output shaft with the cam that drives the pump is on backwards--I KNOW that can be put on bass-ackwards--how did you get the pump out of the way to reinstall the O/D? But run through the electrical diagnostics first.

Second: I wouldn't try a 'flush,' for a couple of reasons; if there is indeed gunk floating around you're all but guaranteed to plug up a hole or small passage in the O/D, requiring a teardown anyway. ATF would be OK for a flush--some use them in gearboxes and O/Ds as practice--but any solvent wouldn't protect gears for long and could seriously damage rubber components. A BJ8 O/D will have rubber O-rings on the operating pistons and could have been retrofitted with O-rings on the accumulator piston.

 

[Healey Nut]

Kinda hindsight now but , you pulled all the transmission out , overhauled and fixed it but didn’t open the OD to at least have a look and clean it out ?
The ODs typically (or the ones I have overhauled) have that grey sludge in them , not 100% sure what it is but I suspect it’s just normal wear n tear of moving parts etc .
I would remove the side plate and bottom plug , pull out the accumulator piston and manually clean it and it’s chamber . Change the piston seals/Orings etc and reassemble it all .
New lubricant (your choice on what you use but 20/50 is mine) drive the car a few hundred miles make sure everything works then change the oil again , clean the OD filter screen , drive again , check screen filter etc etc .

 

[Bob_Spidell]

Quick check on the electricals: Put car in 3rd or 4th (engine off) turn the key on and throw the O/D switch; if you hear a click they're probably OK. Then, press the accelerator pedal and listen for the solenoid dropping.

 

[AUSMHLY]

My take (I'll send you a bill ): First, find out why your O/D quit working; diagnostics, guesses, tips, tricks, etc. abound on this forum and others. If you didn't tear down the O/D the oil pump would not have been touched--it's bolted in--except to get its roller out of the way. My best guess is the collar on the gearbox output shaft with the cam that drives the pump is on backwards--I KNOW that can be put on bass-ackwards--how did you get the pump out of the way to reinstall the O/D? But run through the electrical diagnostics first.

Second: I wouldn't try a 'flush,' for a couple of reasons; if there is indeed gunk floating around you're all but guaranteed to plug up a hole or small passage in the O/D, requiring a teardown anyway. ATF would be OK for a flush--some use them in gearboxes and O/Ds as practice--but any solvent wouldn't protect gears for long and could seriously damage rubber components. A BJ8 O/D will have rubber O-rings on the operating pistons and could have been retrofitted with O-rings on the accumulator piston.

Solenoid goes in and out of overdrive. The pressure gauge I installed over the operating valves showed no oil pressure. I R&R the pump today. A friend spun the coupling flange, I saw the the pump spring compressing/uncompressing. I'll assume the pump is on the cam and hopefully that was the issue.

I replaced both o-ring operating pistons. I replaced the accumulator housing/piston with the AHSpares modified O-ring conversion unit. I have a new oil pump body/spring/plunger. I replaced the ball bearing/spring/plunger for the oil pump and operating valve.

To flush or not. I didn't have any debris in my prior oil changes. The overdrive worked fine, had 2nd gear issues. The guy who was rebuilding the tranny said, if OD ain't broke, don't fix it. I replied this is the time to open it up and make sure nothing needs addressing. He comment, you could find it doesn't work after opening and putting back together. It was a battle to get this guy to work on the tranny and it took him 3 months. As my father would say, pick your battles. So, it's working, let it be I figured. Now I find debris from the OD is showing up in the oil?

Being there is gunk floating around, I'd think I should address it and get it out. If I don't it will eventually plug up something. Most likely the pin hole in the operating valve.

I can try and flush the system with multiple 30w non detergent oil changes. New 30w, 10 minutes? Drain, new 30w, 10 minutes. Repeat until clean oil?

Does ATF have a cleaner in it and possibly do a better/quicker flush. Say 10 minutes, drain, repeat with new ATF 10 min, check oil for debris. If clean, drain the AFT, run 30w for 10 minutes to flush out the ATF. Then drain/fill with 30w.

I don't want to do any damage to the gears rubber parts or anything in the OD, so I'm doing my due diligence.

Thoughts?

These 3 photos are of the same drain, same amount of oil in the bucket. Thought on the debris?

 

[Bob_Spidell]

Now I'm confused; you said: "The OD was working, so I didn't open it up;" was all the work on the O/D you mentioned done before the gearbox rebuild, or did you pull it out again? At any rate, with a functioning pump but no pressure the most likely culprit is the ball-bearing check valve on the pump output. I believe it's possible to get to it in situ, but I've not done it so can't help. IIRC, someone on this forum has described how to do it.

 

[AUSMHLY]

Now I'm confused; you said: "The OD was working, so I didn't open it up;" was all the work on the O/D you mentioned done before the gearbox rebuild, or did you pull it out again? At any rate, with a functioning pump but no pressure the most likely culprit is the ball-bearing check valve on the pump output. I believe it's possible to get to it in situ, but I've not done it so can't help. IIRC, someone on this forum has described how to do it.

Hey Bob, thanks for your help. Sorry, not intending on confusing anyone. While the tranny work was being done, the OD has to be removed. I replace all the rubber items in the OD I can get to without taking the entire OD apart. The OD pump can be removed from the bottom, you don't need to open it up.

 

[AUSMHLY]

Update. R&R the pump, now have 510 psi. As suspected, the roller was not on the cam. OD is working after adjustment. Flushed the tranny/OD with 30w oil two times, 15 min run time in gear, while on jack stands. Oil now seems clean. I'll drive it for a little while and drain it to see if it's debris free. Thank you for your input Bob and Healey Nut.