John Morrison Posted November 8, 2023 Report Share Posted November 8, 2023 Hi all, I run a TR 4 fitted with an A type overdrive that I just love to bits. For me it makes the car half as much fun again, and third to O/D third is just great around our country roads. But a question, we have a group member looking to add an overdrive to his TR4. Ball park figure these days all-in is around £2.5K for an A Type, all done, J TYpe several hundred pounds less. Now I don't know much about J Types, and the ones I have driven seemed to having a delay on engagement which rather lost for me some of enjoyment. Does a J Type have a delay or was I just unlucky with what I was trying? Dp you think itw worth paying the extra now, and would my man get it back if he ever sold this car/ John. Quote Link to post Share on other sites
TR NIALL Posted November 9, 2023 Report Share Posted November 9, 2023 J Type here in a TR6 with no delay. Quote Link to post Share on other sites
rcreweread Posted November 9, 2023 Report Share Posted November 9, 2023 John -a properly set up overdrive, whether it be an A or J type, should engage quickly irrespective of the type - as they wear, response times will usually slow down - type of oil will also have a bearing. In use, the J type is maybe a little more reliable because it is less reliant on the electrics compared to the A type, and unless modified to do so, doesn't work on 2nd gear like the A type. A genuine TR J type is probably a bit cheaper than £200 less than an A type, but if you want an even cheaper entry level, then simply use a saloon overdrive box ( a j type one is easier) which are a lot cheaper and fairly readily available - you need to modify the gearbox mounting, use the saloon clutch plate and change the rear flange and accept an inaccurate speedo. However this will impact the end value of the car - to get the most value out of the conversion, a genuine A type TR unit will always create the most end value - just my opinion! Cheers Rich Quote Link to post Share on other sites
TRTOM2498PI Posted November 9, 2023 Report Share Posted November 9, 2023 J-Types operate differently to an A-Type. A J-Type, by virtue of the way it operates, is not as fast as engaging as an A-Type, period. If you think a J-Type is quick, you should try an A-Type. If you really want a faster engagement, try a competition spec one. If I was considering fitting o/d to a TR4, I would fit what it would have had originally (A-type). I cannot see the cost difference being that much between the two, and the car will always be more desirable when you come to sell it with an A-Type o/d installed. Cheers. Quote Link to post Share on other sites
Hamish Posted November 9, 2023 Report Share Posted November 9, 2023 Love my A-type once sorted by Pete cox and son. And logic box ! Quote Link to post Share on other sites
Andy Moltu Posted November 9, 2023 Report Share Posted November 9, 2023 The A type and J type boxes have different mountings on the TR. So if you wish to fit a J type box to a TR earlier than the CR sixes you will need an adaptor for the mountings. Just over £100. The A types generally engage faster, the J types are considered more reliable as well an not requiring a relay to operate the solenoid. On the TRs the inhibitor switches operate the A type on 2nd 3rd 4th. J type on 3rd &4th, but that can be changed by fitting an extra switch to the top cover and minor tinkering. Allegedly this was because of concerns about the torque of the 6 cylinder in second gear. However it handles the torque of the Stag v8 so not a convincing arguament. Quote Link to post Share on other sites
trchris Posted November 9, 2023 Report Share Posted November 9, 2023 I agree with above fit a A type as what it should have and a TR one at that Chris Quote Link to post Share on other sites
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