A Type Overdrive Slow To Engage (again)

[julianhensman]

I know this topic has been covered in other posts, but I haven't really figured out what order things should be done in, so thought I would ask here again. I also note that a recon A type unit is only £400 (although thats a lot of money), so lots of paid for labour by experts is probably not the way to go.

 

The problem is that the unit takes ages to engage. After I have thrown the switch, it will take up to two minutes to engage when the gear oil is cool and 30-45 seconds when it's hot (this immediately suggests an oil problem to me?). I am trying to go through a process of elimination to figure out what is wrong. I am working on the assumption that the sliding clutch is not slipping. I assume this because once the unit is engaged, it never slips out or even hints of slipping. Is this a safe assumption?

 

If this is true, then my next deduction is that the clutch is simply not engaging fast enough, and if it is not slipping, then the pistons cannot be pushing with enough pressure or certainly not quickly enough. Working backwards, this could be caused by the pistons somehow sticking but this seems very unlikely to me? This then must mean that oil does not reach the pistons fast enough. If the oil feed is slow, this I guess could be caused by a multitude of things. So this time working forwards I plan to check the following.

 

1) Oil. I know the oil is in good condition and at the right level, but as I have never drained and refilled myself, I don't know what grade it is. First thought then, drain and refill with 30ish grade? I guess I would need to check the filter too.

 

2) Solenoid engagement. I get the expected "click" when engaging and have been under the car and seen it operate. The plunger pulls the lever and although the plunger can be pushed into the solenoid slightly further after operation, the lever reaches its stop and I am sure it cannot go any further up. So this leads me to believe that the operating valve lever is also therefore operating the valve spindle (see later comment though). But can/should this be adjusted?

 

3) Operating valve. I am guessing that this may be one of the prime areas for investigation and it may well simply be clogged to the extent that the oil does not flow through very fast. But, I am wondering how this can be possible with over 300 psi? I suppose attachment of a pressure gauge that then indicates good pressure indicates good pump, oil, accumulator and clear oil passages up to the operating valve. But what would lower pressure indicate?

 

4) Pump. As the engagement of the overdrive is slow every time, but does eventually engage every time, I am thinking there is nothing wrong with the pump. If it was somehow losing pressure, or was not pumping, the unit would in theory not engage at all. Is this true?

 

5) Accumulator. Another prime target. I am wondering if the accumulator is not charging properly. However, if it was not, I am guessing there would be no oil fed to the main shaft, which in turn I think would have had other consequences. But if it was not charging, this might mean the pistons were being operated directly by the pump, which might explain the slow engagement? I was also thinking that perhaps the pressure relief valve might be leaking with the same effect? Or could the accumlator spring be broken?

 

6) Oil passages generally blocked. This is my last thought and a possibility I suppose. Don't know how I could fix that without a complete strip down.So, my next plan is to check the operating valve. As this means removing the transmission tunnel etc I thought I might try to bounce these ideas off the forum first! I was wondering though whether there is any adjustment anywhere to change the lift of the operating valve spindle or the solenoid lever travel, just to make sure the valve is actually opening far enough?

 

So I'm wondering what order I should check things in. Any help or suggestions you can offer would be gratefully received!

 

Thanks,

Jules

[AlanT]

You will find all the information you need from here:

http://www.buckeyetriumphs.org/technical/AOD/AOD1/AOD1.htm

 

or here

http://www.vtr.org/maintain-index.shtml

 

From what you describe the pump can't pressurize the accumulator. So its a pump fault or the accumulator leaks.

 

None of this is too hard to fix. Accumulator you may be able to do with the unit in the car.

 

Where in the country are you?

 

Al.

[julianhensman]

Hi Al. Thanks for the response. I have read the buckeye stuff with interest and will check out the other link now. Am near Biggleswade, Beds. Is it possibly / easy to replace the pump in situ? It sits above the oil drain yes?

 

J

[RogerH]

Hi Julian,

before you attempt repair/removal etc have you checked that the O/D operating shaft lever rigging hole is aligned with its hole in the O/D body.

The lever is on the righthand(offside) side.

You may need to remove the GB tunnel.

If you are lucky there may be an inspection panel to see what's going on after carpet removal.

 

Roger

[julianhensman]

Hi Roger, no haven't done that yet. I have a replacement tunnel which doesn't have inspection panels. In fact, that is the reason I started the thread as I wanted to see if there was anything else I should do first before the rigmarole of removing it. So do you think that the next sensible thing to do?

[RogerH]

Hi Julian,

if the lever doesn't go far enough then the pump will not work as well as it should.

 

Tunnel removal is a bit of a phaff but is straight forward - seat out, 'H' Support (with the control cables removed) out, carpets off, tunnel off.

 

If it is not the rigging hole then you would almost certainly have needed to take the tunnel off anyway.

 

Roger

[dingle]

I agree with Roger that the adjustment of the operating shaft lever should be the first thing checked, but just using the 3/16" pin may not work. As pointed out in the Buckeye articles, wear in the linkage may require going slightly past the point where the pin goes into the hole. Also, if you have to remove the tunnel, it may be helpful to fit a gauge to check the pressure.

Berry

[dingle]

After re-reading your original post, I think it could very well be the adjustment of the operating valve as insufficient lift of the valve could increase the engagement time.

Berry

[julianhensman]

OK, I will give it a go and post the result. May be a little while before I can get round to doing it though. Many thanks in the meantime for the input.

Jules

[julianhensman]

Hmmm, one more thought. Any ideas where I can get a pressure gauge to fit?! I may as well check that whilst I'm there.

Thanks,

Jules

Edited October 22, 2012 by julianhensman

[AlanT]

Quite hard to get. There are loads of US websites like McMaster-Carr that carry these. But they tend not to ship internationally.

 

You are also going to need an adaptor to mate it with the OD. I bought my gauge from a guy in the US who made at batch, complete with adaptor, for the AH owners club. Had some leftover.

 

You want something like 500psi and oil filled or it will come to bits.

 

If you test in the car the traditional method is to jack up one rear-wheel and run in top gear. This is way too risky for me.

 

You can just get hold of the lever and move it by hand with the thing running. No need to do anything with the solenoid. Just move it. They dont bite.

 

Al.

[Stoker]

Hi Jules

 

A trip to your local hydraulic specialists and if they are as helpful as mine they will supply gaige and fittings etc at a very reasonable cost.

 

John

[dingle]

Jules-The gauges are pretty easy to fab, if you can't find someone willing to loan theirs. Mine is copied from the one pictured in the Buckeye A type OD article, part iv. I used a 600 psi glycerin filled gauge that has a 1/4" male NPT fitting. Next is 1/4" NPT connector followed by a 3" piece of 1/4" pipe. The last piece is an adapter-1/4" NPT female to 1/2"-20 male (the size of the operating valve plug). Making the adapter is an easy lathe job, I don't know if are available from a suppier. The length of pipe is necessary to clear the top cover of the trans. You may find a slightly longer length needed, depending of the length of the adapter. My gauge measures about 5" from the gauge fitting to the tip of the adapter. I believe the operating pressure should be 450 psi with the smaller accumulator as used in the TR6.

Berry

Edited October 22, 2012 by dingle

[julianhensman]

Guys, thanks very much again for all the input so far. Very useful.

 

@Berry - I decided to order a US guage in the end as am too busy to source any other way - interesting post though, thanks. I ordered from Jay Holecamp in Wheaton Illinois at this link:

 

http://www.webring.org/hub?ring=triumphautos;id=24;ac=ImRE%BC%AD%9F%F4%E3%D1%CB%3E%5E%5D%3C%2F%1E%BB%BB%88%CD%A8%82%80w%7BN%25%7D%11%1C%EE%ED%DB%AB%BF%C5%9D%7DH%17%3B%3B%1E%F4%FB%CF%92%A4%89%D9%60u_%2F3%02%1D%E2%D2%9A;go

 

Jay was very helpful. His website ordering link didn't work for me so I emailed him and he sent a PayPal invoice which did work. Looking forward to received the tool! Will comment later on quality etc.

 

I hear that the safest way to do the lever test in situ (without moving!) is to disconnect the prop shaft. I am hoping this is fairly easy once the tunnel is off. Once it is off, pulling the level at a given rpm should simply alter the speedo if it engages. Any advice on this front? May be a silly question but I have to ask it - would it be too dangerous to simply attempt to do the test whilst actually driving the car with the tunnel off?!!!

 

Many thanks,

Jules

[RobinTR6]

Jules

 

just been through all this. Have driven and operated the lever, had it up on ramps and operated the lever. Although you can drive and do it..I wouldnt , its is difficult to find the lever and keep an eye on the road. Jack up back end , axle stands, bricks under front wheels. Did this off and on about 20 times so can vouch for it. I had the opposite issue , wouldnt come out of O/D. Eventually removed the operating valve and replaced, the new one was 0.5mm diameter wider, worked straight away. Removed and replaced accumulator spring, it was a bit tired, cleaned accumulator valve and replaced the ball bearing there and on operating valve. Filled with 20/50 and drove a couple of hundred miles to dislodge any gunk in the narrow oilways etc etc. Now running fine however O/D wont kick in unless I back off the accelerator a bit, pressure issue maybe.....I was advised that my O/D was running 410+PSI so pressure shouldnt be an issue, be interested to see what you discover.

Edited October 24, 2012 by RobinTR6

[julianhensman]

Hi Robin and thanks. OK, may try the ramp method then - axle stands in my case. Do you think removing the rear wheels once on the axle stands would help reduce vibration and make it more stable or is this just asking for trouble in case the car does come off the stands?!!!

[RobinTR6]

I left my wheels on, axle stands where the chassis trailing arm sections and the bits running along the sills met (width), bricks under front wheels to stop her moving, start and gentle, clutch engagement (I started off in 2nd gear) increase in revs, managed to get to 3/4 k revs in all gears without issue, note everything done gently.

 

Yep I was worried at first but once done the first time it was like falling off a log (yep pun intended). I think if youre careful and ensure its well positioned and front is locked in place then you wont have a problem (well apart from getting the O/D working that is). If you need to check anything else let me know as I said, just spent the last month of so doing the same. Good luck

[Tim D.]

Running with the propshaft undone is also not a problem.

Cheers

Tim

[RobinTR6]

If you undo the prop mark the mating flanges on gearbox and prop so you reconnect as they were.

[julianhensman]

Hi All. Am slowly trying to pluck up courage (and find time) to start this. When I remove the gearbox tunnel, will I need any sealant when replacing it, or are they just rubber seals? Need to make sure I can get the car back on the road within a few hours!

Thx.

[AlanT]

If you still have a cardboard tunnel I would take the opportunity to replace with the Revington two-part fibre-glass one.

 

Check this out and you will see the obvious benefit is that you can do OD and speedo maintenance without removing the H-frame.

 

Tunnels seal with rubber gaskets, easily available, but you may find the existing one has gone "sticky" or has been "repaired" with sealant. This makes this job a painful, messy business.

 

Disconnect prop is the safest way to do this investigation.

 

Al.

[RogerH]

Hi Julian,

don't do what you intend doing in a rush.

As Al says the cardboard tunnel works OK but the plastic or fibreglass tunnels are better.

If you decide to put inspection holes into the tunnel (O/D rigging pin, oil filler etc) then make sure that the carpets and underlay are removable - the 'H' frame may trap them.

 

When you come to do your tests/inspections firstly energise the O/D solenoid (engine off, Ignition on, 3rd gear) and make sure the offside rigging pin holes align.

If they don;t then adjust the solenoid till the holes do align - go for a test drive.

If they do align then go for a test drive, select O/D and apply some pressure to the offside lever to see if it will engage - if yes then adjust solenoid. If no then you have internal problems.

I assume you have oil in the box. I used SAE 40 gearbox oil but other people use all sorts with apparent success.

 

Regarding seals - the two big floor seals can be glued to the floor pan to stop migration, The front one can also be glued in place whilst inserting the screws.

 

Roger

[AlanT]

I glued the rubbers to the fibre-glass tunnel. But I did it in an odd way.

 

I positioned the rubbers on the floor-pan using double-sided tape. I put PU sealant on top of the rubber and popped on the tunnel. I bolted it down but not too hard.

 

This means that the PU takes up errors in the tunnel and ensures a good seal.

 

Al.

[julianhensman]

Hi All,

 

I hope everybody has enjoyed a good holiday season. It is some time since I started this thread but this weekend I finally got around to doing the work and thought you may be interested in the result

 

First thing we did was get the gearbox tunnel out. Not the worst job but not a doddle either. If you are planning this, note that you need to take both seats and the H frame that holds the radio out first (it's also a pig to get back in but that's another story). We then checked the operation of the solenoid and it appeared to be operating enthusiastically and there were no apparent problems with the soledoid coils (could not prevent it pulling in, could not pull it out when it was in, released fine). So we decided to leave it in situ without further tests (you can test the resistance etc) and look elsewhere.

 

The next thing was to check the locating lever on the other side of the geabox. Now I meant to take a photo of this with the tunnel off as for some strange reason, there are very few photos available of this side of the gearbox in manuals and on the web, but unfortunately, I forgot, sorry! Anyway, the locating lever moved downward on operation of the solenoid as it should, but ... when in the engaged position, I found I could still manually push the locating lever down another millimetre at least. I checked it's location as described in the manuals by inserting a 3/16 drill bit into the locating lever hole and ensuring it located into the hole in the gearbox casing - it fit perfectly. This was a little disheartening as I was hoping to find it short, which would immediately explain a non-opening valve. Anyway, we progressed further by removing the valve plug (thoroughly cleaning the area with petrol first (you must make sure absolutely no dirt gets inside the valve), gently taking out the spring, the plunger (with needle nosed piers) and the ball bearing (by cleaning first with a bit of kitchin towel and then using a bit of blu-tack on the end of a pencil to lift it out - don't drop it or lose it!!!). We then checked the seat where the ball bearing sits - clean as a whistle with any residue oil absolutely golden in colour. No problem there then.

 

Despite the locating lever locating properly, as my original suspicions were that the operating valve was not opening far enough, and as Buckeye Triumphs have also done an experiment on valve lift finding that only 2-3 thousandths of an inch make a difference (check here for that excellent article: http://www.buckeyetriumphs.org/technical/AOD/AOD4/AOD4.htm - 80% of the way down the page), I decided anyway to try to adjust the pinch bolt so that the locating lever would travel as far as it could when the solenoid operated. This adjustment was done by switching the solenoid on, loosening the pinch bolt, pressing down to the fullest extent on the locating lever and retightening the pinch bolts. Interesting to note here is that after the adjustment, I could still bet the 3/16 drill bit through to locate in the casing i.e. no discernable difference from before! Then we went for a quick test drive (Safety Note: Take great care if you ever do this with the propshaft exposed - NOTHING should dangle down around that area. If you get a coat or scarf caught in the propshaft whilst you are driving, you are likely a gonna - no joke). Result: the overdrive engaged with cold oil in about a second! I also had a pressure gauge on at this point (thanks to Jay at http://www.webring.org/hub?ring=triumphautos;id=24;ac=ImRE%BC%AD%9F%F4%E3%D1%CB%3E%5E%5D%3C%2F%1E%BB%BB%88%CD%A8%82%80w%7BN%25%7D%11%1C%EE%ED%DB%AB%BF%C5%9D%7DH%17%3B%3B%1E%F4%FB%CF%92%A4%89%D9%60u_%2F3%02%1D%E2%D2%9A;go) which read 380 PSI at peak and showed a drop when the overdrive enganged, building back up to full pressure again within a couple of seconds afterwards.

 

So to summarise: The original problem was that the overdrive was taking a long time to engage. It would disengage from the direct drive after about 10-20 seconds, then would be in a state of "limbo" whereby applying load would accelerate the car, but releasing load would disengage the drive altogether with the revs dropping down to tick over, then after about 2 further minutes (depending on oil temperature) of driving would engage into overdrive. What was actually happening was that the flow of oil to the pistons was far too slow, such that the filling of the pistons with oil (and therefore the travel of the internal clutch) was also very slow. This slow movement was caused by insufficient oil flow owing to the valve not opening far enough, hence the adjustment fixing it. The odd behaviour when "in limbo" was caused by the fact that the internal clutches had travelled far enough to disengage the direct drive, but not yet far enough to engage the overdrive. This meant that the drive to the rear wheels whilst "in limbo" was being provided purely by the one way clutch (!), which explains why I could accelerate but on coasting, the revs would go down to tick over.

 

I would like to thank everybody who contributed to this thread and also I would like to thank David Dawson who kindly popped round to offer expert advice along the way which was extremely welcome!

 

Kind regards,

Jules

[AlanT]

Thanks for the update. It's always nice when people tell us how they got on.

Pleased that you resolved this quite easily.

 

The safety-advice about the prop-shaft is BRILLIANT. This is the kind of thing that is so easy to get wrong.

 

You have a little wear and backlash in the operating lever and so its not lifting the valve enough. So the drill-bit set-up does not quite work.

 

Don't think mine does either. But on a test-rig you just fix this kind of thing without really bothering.

 

Al.

Edited December 31, 2012 by AlanT