[TR] Triumphs Digest, Vol 9, Issue 136

Fri Jun 10 19:10:10 MDT 2016

 In sounds like this is a  J type overdrive whereas I would have thought that it would be an A type.  I say this because messing about with the pump on an A type would not necessarily change the oil pressure whereas on a J type it would.  The pressure on a A type is controlled by the accumulator piston spring. I don't no whether you can get 500 psi on an old A type overdrive. The overdrive is not working properly because the brake ring is slipping. I think that the pistons that apply the force to the brake ring may be leaking.  Just because the pressure relief valve  on the pump has be reseated doesn't mean the relief pressure is correct. The spring might be weak.  I strongly suggest that you read the overdrive information on the Buckeye web site. 
Stuart A Greenwood 

    On Friday, June 10, 2016 4:37 PM, "triumphs-request at autox.team.net" <triumphs-request at autox.team.net> wrote:

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Today's Topics:

  1. Overdrive issues (Rye Livingston)
Transmission update - for those reading about this for the first time, this is a 1960 TR3 with a TR4 OD transmission. Yesterday they said it's basically a TR250 transmission. The whole transmission and OD was rebuilt by a British car specialist of 40+ years.  His employee has also been working on British cars for years, and is a transmission specialist.  They've rebuilt literally 100s of transmissions and ODs.  They had 4 OD cores on their bench as they were showing me different parts of the system.
Symptom - when I'm accelerating and flip the switch for OD, it doesn't go into OD until I let up.  When in 2-3 or 4th gear, OD engaged, and punch it, it will downshift like an automatic transmission while I accelerate, then shift back into OD when I let up.
I'm not technical enough to know how to describe all what they told me, but I'll try.  First off, I forwarded the comments when I posted this issue a couple of weeks ago, and keep in mind it's not the easy/obvious things.  They've checked all the electrical, solenoids, ground, oil type, etc.  When in OD it's not slipping.  They've tested the PSI with a gauge attached while driving down the expressway, and jacked up with the wheels off the ground.  
The issue is that it's not getting high enough PSI.  It's over 400 PSI, but it needs to be 490 to over 500, I think they said 520.  They've taken the transmission back out, taken the OD all apart, and there's nothing obvious. They've changed the piston in the pump. Originally it had a pump that would shift softer because I've got a torquey engine and the other pump, which they called a competition pump, would be hard on the differential, but they've got that one in the car now.   They showed me a seal that goes around that piston and said the new seals are rubber and they got one like the original style that has some sort of metal reinforcement in it to hopefully make a better seal.  Not very clear I know, but hopefully that makes sense.  They've checked the seats where a small ball bearing must make a perfect seal, they all look perfect.  They said everything looks absolutely pristine.  No scoring down passageways that might not allow maximum PSI, etc.  They also showed me the lining on a Sun gear they had on the beach, and said mine looked good and the rivets looked original. They put it all back together, went for a test drive, and that didn't fix it.

They've spent literally 20+ hours on this transmission, plus several more hours doing internet research on the problem.  As they described everything and what they've checked, which seems like everything, I said I'd send out this email to the list.  Not that they haven't tried everything, but I'm hoping there may be one little nugget of info they haven't tried, or a test they can run, that will lead to the solution.
Thanks,
Rye Livingston
Triumph Travelers Sports Car ClubActivities Chairman1960 TR3APH: 530-FIND-RYE
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