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General Tech Overdrive--Afraid it's Serious

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Can I rap from beneath the car or do I need to be hitting it from the disassembled interior?
 
Just a little background on the OD. There is a single piston pump, which pumps one stroke for every turn of the drive shaft. It sends the fluid to a spring loaded accumulator piston, which "stores" the pressurized fluid. The solenoid moves an arm, which turns a rod thru the entire OD to the other side, where another arm on that side of the rod pushes a valve. That valve sends the accumulator fluid to the barrel pistons to engage the OD...and it also allows the fluid to vent from the barrel pistons to release it. If the arms are not adjusted perfectly, you can end up with an OD that will not engage, or in your case, will not release.

Waiting overnight should allow the pressure in the accumulator to bleed off, regardless of any problems with the valve. You should then be able to release the OD with a few well placed raps around the outside of the OD ring. Then, once driving again you will build the pressure back up, allowing the OD to engage again...either from being selected, or from a valve problem.

When I rebuilt my OD, I used non-detergent 30w, straight out of the manual recommendation. It stuck every time I engaged it. I could pull in the garage and tap the case and it would release....only to stick again the next time I engaged it. Randall recommended the MT90 oil. I switched to MT90 and have not had an issue with sticking since.
 
OMG!! I banged and banged at it. My baby I just rebuilt. It hurt so much to hit it with a steel hammer. But it’s now free and rolling again. It’s alive. It’s alive. The Italians are geniuses. Pure genius. Thanks guys!!

Now what do I do? Never put it in OD? Dump out the gear oil and put MT inside. Drive it hard in OD? Curious your thoughts now. I still really don’t want to pull that interior out again. Won’t a sticky valve clear out? Thanks again. I’m going for a drive. Mario’s Pizza.
 
Will do. I tried a fat brass drift at first. Then a plastic dead blow. My lead one was too wide for the job. I’ll buy a new one for this job. My mechanic buddy says I need to drive and wear in this new but unused OD, just avoid being away from home and needing reverse.
 
CJD, I've read several posts about the overdrive unit here and elsewhere, plus the LdN manual, and you provided more useful info in your post than all the others combined. THANK YOU. I will tremble a little less fearfully when I finally work up the guts to try engaging my OD.

KVH, I second Randy (TR4Nut)'s suggestion to drain and "rinse" with ATF before refilling with MT90. ATF has mega detergents that can dissolve and carry away a lot of sticky sludge. A few drain-and-fills with a good name brand actually resurrected a HydraMatic that I had burned up (it was locked in gear and literally had smoke pouring out of it). ATF is now my go-to when a WD-40 soak won't cut through the crusty, oily gunk on old hardware.
 
Glad you got it released...especially before anything was damaged. If you read through old posts, you'll see that many owners pressed the issue until their OD's had to be rebuilt to replace the one-way clutch.

I would strongly recommend changing the fluid to MT90. It's pricey, but it works. There may be other fluids that work, but why mess with them when we know the MT90 works?!? Once you have the MT90 in, just use the OD normally. You shouldn't need the mallet ever again. I did use a steel hammer on mine when it stuck...although I wouldn't recommend it, ever. It's not so much how "hard" you hit it, but mainly that you get it to "ring" just enough to break the barrel loose. If you use steel on aluminum you have to use a lot of restraint! If the case gets warped from whacking too hard you will end up with even worse problems.

Glad I could help, J! My biggest fear working on these cars is that some of the parts are getting hard to find...
 
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Thanks all. I’ll post some pictures of my rebuild and restoration.

I’m fairly proud of it, though I know that there are some real technicians out there that could put me and a lot of us to shame.

I rebuilt an overdrive unit myself (but with the help of this forum) a number of years ago on one of my other Triumphs. I didn’t do any work on this overdrive, as I had both the transmission and overdrive rebuilt by a good local shop.

What I would like to add to the discussion is that everything we read and learn on this Forum, including from the official Laycock Manual, seems to be right on point.

That Manual states that an overdrive that will not disengage is usually not suffering from an electrical problem, and only sometimes from valve-related issues, those being fairly easy to isolate and identify.

I was surprised by the clear focus on a sticking clutch and the necessity to smack the the brake ring with a hammer. It is just so counterintuitive to think that a problem that serious – – you essentially can’t move or go anywhere – – is resolved by reaching for a blunt force weapon and smacking your precious classic vehicle with it like an angry, frustrated gorilla.

So, what I would add to all of this is to trust what people around here say, and especially the literature, when it comes to any LBC problem, including in this case a sticking overdrive that has recently been rebuilt.

After a long drive this afternoon with the overdrive working flawlessly, and then releasing with no problem when I arrived home, I’m hoping everything has been resolved and that I do not need to remove the interior of my vehicle (yet again) to get at any of the valves. And, as I stated, the operating rod, lever, and valve seemed to have been working fine, pointing once again to a seized or stuck overdrive clutch, and, of course, the necessity for what? A hammer.
 
Had that happen to me with newly rebuilt overdrive. Metal hammer and hit it like to you mean to bust the casing. After it breaks loose then you will need to “break it in” Or it will continue to stick. Put it under strong power and then let up on it abruptly, preferably going up a hill. Do it several times until it operates correctly.
 
Thanks Marvin. I’ll do that today.

just thinking: A good rule while testing might be to avoid needing reverse at any time during the test drive; i.e, no parking against walls.
 
That happened with my newly rebuilt OD. I had not connected the drive shaft so I was able to tell it was locked up. A sharp rap with a copper hammer released it. The guy that rebuilt it recommended driving up an incline and switching into OD and out of OD to bed the brake drum in. Seemed to work.

David
 
As has been mentioned this seems to happen with newly built O/Ds and may fix itself in time. Mine did it on my TR250 (rebuilt later J type). Would not disengage immediately after using. If I let it sit it would after cooling off. Eventually it went away after the first few months of driving the car. My theory is the clutch was tight and as mentioned marble needed bedding in or slight wear to release more easily.

You can break the O/D by going in reverse, but I hear it let's go with a pretty big bang, so you will know it when it happens. I would drive the car, use the O/D, and make sure you park it where you can front out without using reverse.
 
KVH said:
I just took a drive and used my overdrive for the first time since it was rebuilt in the shop 3 years ago. This was its first time in service. It seemed to run fine, but my transmission is now locked up. It will drive forward, but it will neither roll backward nor drive backward. Reverse seems locked. I was thinking my brakes locked up, but I'm certain that can't be it. This is a total lockup for anything moving the wheels backward.

Did I wire something up wrong? Do I need to take the entire interior back out and release a valve?

I can hear my solenoid working, and I'm not feeling any hot wires. I'll dive into the search tool, but wanted to get a jump on any thoughts you folks may have.

Thankfully, I'm retired. If I need to pull it all back out, I guess that's what I'll do. Thanks for any help or advice.
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sounds like the trans is in two gears at once,shift forks?? you will need to pull the top cover...
 
Yes, even though it’s working now, I’m always parking where I can pull front out unless I’m in my own garage. I’m still looking for a good hide hammer.
 
Don’t think I was too clear on my earlier post. As David said switch it in and out of overdrive under load, preferably going up a hill. Later when you know you are out of overdrive, use reverse a couple times then road trip again trying overdrive. Doesn’t take long to bed in. Then ride it like you stole it.
Marv
 
And don’t bother using the clutch with O/D switch? Just lift your foot a bit and flick the switch?
 
Flip the overdrive off and on with foot on the gas, this is only until it quits sticking. Since you have it working now, just do it a couple of times.
 
Marvin Gruber said:
Don’t think I was too clear on my earlier post. As David said switch it in and out of overdrive under load, preferably going up a hill. Later when you know you are out of overdrive, use reverse a couple times then road trip again trying overdrive. Doesn’t take long to bed in. Then ride it like you stole it.
Marv
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I would for sure change out the fluid s may be w some royal purple synchonomax? Glad you got it back it's never a good feeling after all the work that's for sure
 
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