I just realized that I have never owned a vehicle with a functioning overdrive. Ah well, just one more missed experience. :-) Thanks for the very informative video, Elin!
I have fond memories of the Laycock J type overdrive, esp on my Triumph's where you used the gearbox to get you to your cruising speed then flicked the gearstick switch and the revs just faded away and cruised along the motorway a treat. I had one too fitted to a MK1 Ford Transit SWB campervan, the previous owner had fitted it with a 3 litre V6 setup prob from a Consul and had included the overdrive plus changed the back axle to a Jaguar diff and this Transit could shift like nothing else then once up to 70 flick the switch and cruise all the way :D
Thank you for the video. I think my limitations do not stretch to rebuilding gearboxes, but it is interesting to see how they function and the overdrive. My interests with your videos are more about the body and chassis repairs , maybe also painting and rust treatment, which is about my skill limit I think. I do admire the way you just pull a gearbox apart. It is beyond me, maybe if I was younger I would have tried it.
👍I have to say, not at all boring to me! Great info for anyone who needs to rebuild a Triumph gearbox or is considering an overdrive conversion. One thing I noted was the oil. You used 30w non-detergent. With a used OD where there may be some wear, 40w might be needed. Or 20w50. You mentioned "engine oil" though... Needs to be non-detergent or "racing" oil, especiall with the OD and its hydraulics. Detergent oil will foam up and that can cause problems. Also be sure any oil is safe with brass, doesn't contain sulfites, for example... That can damage brass parts used in these gearboxes.
Very interesting!! I liked the way you bench tested it. Those overdrives were great fun to have. The one I had (J type I think) gave you 6 gears effectively only operated on 3rd and 4th gears. On road conditions the response from the gear lever switch to the actual overdrive was instantaneous in either direction. Great video, learnt a lot, thank you very much. Good luck from Spain!!
Will you be doing a rebuild of a J-Type OD itself as well? Having got part way through the A-Type rebuild before abandoning it, it would be great to see the same strip down and rebuild of the J. Great series BTW, and not at all boring!
Thank-you, thank-you. Really useful. I have J type OD and main shaft from a Dolomite sprint that I intend to fit to my non OD 74 TR6 G/box. This sequence of videos is going to be a big help. The switch locations for all the functions (Reverse, Neutral and gear lock out) moved to the back of cover near the shifter on the 74 onward TR6. The boss on the top of the box were no longer machined. I wonder if the difference between A & J is that the oil pump for the J can't create enough oil pressure to reliably operate the OD when main shaft is spinning at a lower speed in 2nd gear ?
Yes a lot of people laughed at the name "Rimmers"... then they saw their bank balance after a light shopping spree and didn't laugh much there lol I spent a veritable fortune with Rimmer's when I did my Triumph Dolomite 1850 HL, the only nut and bolt restoration I ever did... then my brother wrecked it... it was heartbreaking.
Not boring at all. I actually prefer the engine and transmission videos. I am currently rebuilding my gearbox, but not the J type overdrive since it seemed to be working fine. However, I was seeing leaks at some of the bolt holes at the adapter. What are your thoughts on using a little thread sealant on those studs during reassembly?
That is a good idea. I actually never thought about the fact that the adaptor bolts to the main casting and the treaded holes are open to the inside, aren't they?
Elin, thanks for the gearbox and overdrive rebuild series, very interesting, especially the swap from A-type to J-type. The A-type on my 4A operates on 2nd, 3rd and 4th; the J-type on my Stag is limited to 3rd and 4th. My understanding is that this restriction was introduced because the J-type is not so robust and cannot take the extra torque of 2nd gear. If your top cover is from the A-type are you going to modify the limit switches/wiring to ensure that OD can only be selected in 3rd and 4th?
That is a good question, but I think this is a common misconception. The fact that J-type is limited to 3-rd and 4-th only has nothing to do with the overdrive itself. I might be wrong, but here is my opinion why: 1. Overdrives experience the same torque in all gears. They have a ratio and that is what determines the torque. No matter what gear the transmission is in, the chances a not so robust overdrive to fail are the same. 2. Early cars (I am talking about TR6, not sure about Stags) came with an A-Type OD (optional) and it happens that early cars did not have a neutral safety switch. At some point (I think in 75 but not sure) they switched to a J-type overdrive and at the same time they introduced a neutral safety switch. Of course that switch needed to find a place on the transmission and the engineers decided instead of adding another switch to use the place where the 2nd gear switch was going. They just thought a 2nd with OD is not used that much anyways... and took the spot. In fact on the 1975 TR6 overdrive harness there are still connectors for the 2nd gear switch, but they are not connected to anything. Again, tis is my opinion only. I might be wrong
Hello Elin, There is a J Type OD which came off a Stag for sale in France at present for a reasonable asking price (350EU) but of course it is an unknown quantity. I remembered you had a damaged one ( perhaps it was an A type) so if you wanted I could buy it and arrange shipping. Just a thought , not a scam. THanks again for your great videos. I am missing my 73 TR6 sitting in New Zealand!! Oh one last thing. I owned a TR6 in about 81 and it had OD on 2,3 and top so an A Type. My "new" 73 has the J Type but I own a second set of running gear including an A Type and mounts. I prefered having the OD on 2nd as well , just great for overtaking. Before I decide to change out the J type I have been told teh J Type is stronger and more reliable. What is your opinion on A vs J, please. Regards .
Thanks Peter, but I don't think it is worth bringing a heavy unit from Europe all the way to Canada. I've only driven cars with an A-type overdrive and I can't express an opinion, which one is better. Actually I just responded to a comment above, which mentioned the J-type s not so robust as the A-type hence the limitation on which gears to work with. I think this is a misconception. I think they decided to use the 2nd gear switch for the neutral gear switch, which they introduced at the same time they switched from A to J-type.
@@RustyBeauties Hello Elin. Many thanks for your feedback. I did a search on this topic and found this interesting link .. the post from Motorsport Mickey was particularly interesting in giving the reason for the change to J type being the near instantaenous engagement of the A Type led to cracking of the diff mounts on IRS cars -- sounds plausible. If so I will stick with the J type but I do find it is indeed slow to engage compared to how I remember the A Type..All the best..
@@peterwilson2588 have in mind that here I am engaging the overdrive when the output is spinning with 1500 RPM. In normal conditions you would engage it at around 3000 on third ( that is the output, not the input) and maybe up to 4000 on fourth gear. This means the pump will build pressure much faster.
Maybe I missed it in all the excitement, I’m curious what car did the J type overdrive come from and the did the OD adapter fit both the A type and J type? As always, great series.
It is from a TR6 and no, the plates for J-type and A-Type are different. Actually the A-type is an actual flat plate. The J-type adaptor is like 3" body
I know the D type OD in my Volvo only is set to function in fourth, TR 4’s A type OD function in third and fourth and its death to operate the OD in reverse, but are there any concerns about operating in first and second or running through the gears when in OD?
The only problem I see is the pressure will build much slower on first and second as the output shaft will operate the pump at a much lower rate. So it will take time to engage, but once it is engaged there is no reason why you couldn’t use it.
A types should operate in 2/3 and 4th. J type overdrive operates in 3/4 only. Yes, reverse with the overdrive engaged is death so it’s important that it’s set up properly and your switches are working as they should.