A-Type? No, J-Type Overdrive! - Part 2 - Let's Switch

[@timmarsh6754]

This is perfect! I will shortly be adding a J-Type to a TR6, so this couldn’t have come at a better time for me! There are definitely several ‘gotchas’ that I would have fallen foul of, so great to see you explain the whole sequence. Thanks Elin.

[@JB_WI_Triumph]

When I did my transmission, I had to switch to a new case. I moved that reverse lever and its splined shaft to the new case, but didn't realize that you need to adjust how far the peg on the lever engages the sliding reverse gear. The tranny worked nicely on the bench test, but soon after driving on the road, I got stuck. I was in reverse, tried to shift to first and couldn't. I couldn't go back to reverse either. The peg on that reverse lever had escaped the groove in the sliding reverse gear. If you don't mess with that lever in the case, you are probably just fine, but having learned about this the hard way, I would inspect just to be sure it engages far enough as you put it together. From what I understand, you can only properly adjust it with the tranny completely disassembled (unless you, in an emergency, loosen the nut on the outside and smack it with a hammer to move the peg inward).

[@nigelbarton8350]

I think you made the disassembly of the main gearbox harder than it should have been by doing it in the wrong order. First remove the reverse gear and shaft, then pull out the layshaft (think you called it countershaft but in the UK we call it layshaft). The lay gear cluster can then drop into the bottom of the casing, giving clearance to remove the main shaft complete with gears and bearing out of the rear. Lastly remove the lay gear cluster from the bottom. Hope that helps.

[@RustyBeauties]

You are right. I figured that out too

[@markrobinson8539]

Look at time 14:34. When you applied air pressure it blew out at a port at the top right hand side of the pump end. I don't think you were able to keep air pressure in the overdrive unit. It may well do better with oil instead of air and also the port may be closed off by the end casing when you fit it back but it was missing in the test.

[@RustyBeauties]

When I applied air initially the solenoid was already engaged and held the air until It disengaged. It only blew out when I deenergized the solenoid. So this is when the operating valve lets the pressure go in order to disengage the clutch. That is normal. But you are right, oil works better than air. That is how I test A-Type overdrives and it works, but on the A-Type I am able to reduce the spring tension on the sliding clutch. Here I have no access to the springs. Obviously my air pressure is way too low to overcome the spring tension and operate the clutch.

[@markrobinson8539]

OK thanks for the detailed explanation. After my TR6 gearbox was rebuilt for a damaged bearing, I took a long trip in my TR6. Cruising at 70 I engaged the A type overdrive which worked fine but it didn't disengage. I had a long trip and knew that I had better not reverse the car. Fortunately when I stopped and the oil pressure in the overdrive unit dropped it disconnected. After a few hundred miles it all started working properly. I don't think the gearbox rebuilder had cleaned the gearbox out properly.

[@RustyBeauties]

@@markrobinson8539 I had the same issue after I rebuilt an A-type. It turned out to be a sticky lever on the solenoid side. When the solenoid actuated it pulled the lever, but when the solenoid was off the lever wasn't going back due to too much friction. Turned out I put too much gasket maker and made the shaft sticky.... I had to take it partially apart again and clean some of the gasket maker. Good thing it happened during the bench test. You can see it here. kzbin.info/www/bejne/nYfCfJ2qrs2sbs0

[@corylwillrise]

what normally goes where you are applying air? the oil pump runs a mechanical switch hydraulically (sp?) I am guessing?

[@RustyBeauties]

Nothing, it is an oil pressure test port. It accesses' the oil gallery after the operating valve. When the Overdrive and the trans are put together and the whole assembly is on the testing rig, that is where you mount your oil pressure gauge.

[@corylwillrise]

@@RustyBeauties ok I see this operation you are referring to now in the bentley workshop manual. You are just trying to create pressure in the oil gallery in a sort of 'shade tree' way. I get it now. That was a good idea, but the pressure was not high enough I guess like you say. I'm thinking of buying one of the Laycock J type overdrives from a volvo 240 available on ebay, so I'll possibly be trying to do these same operations.

[@johnmoruzzi7236]

I’m confused… if the gearbox came with the damaged A-type O/D and matching output shaft, how is the input shaft now compatible with the new J-type output shaft if one should be imperial and the other metric ? Did someone do a conversion with a later gearbox and it went wrong ?

[@RustyBeauties]

No, the A-type also has a metric shaft, so it matches this transmission, which appears to be a late one and has a metric input shaft from the factory. Therefore the J-Type mainshaft matches as well. However for the A-type you could also buy an imperial mainshaft and use it on early transmissions without replacing the input. That is why I wasn't sure whether the J-type shaft was going to fit. Long story short - there are early and late non OD shafts, early and late A-type shafts, but only late J-type shafts. That is my understanding.

[@davidfidler1174]

Second (just need third, fourth & reverse now!)

[@RustyBeauties]

Haha! No OD?

[@elichristensen8066]

Third with OD engaged

[@skipgould1780]

All right - I'll be third

[@johnmoruzzi7236]

Lobe !

[@RustyBeauties]

I know.... I saw my mistake after I published and there was nothing I could do about it.... I am so upset.

[@williamlucas8793]

I will be Fourth.

[@cheftush]

First