[Fot] A-type OD leaks

Thu Sep 21 09:34:44 MDT 2023

Hi Joe B..

Henry says " you need to line up two sets of splines in the OD unit "

This is very important, as I learned the hard way the first time that I put
an OD back together.  I thought that I had the splines line up, but in fact,
I only had the first set lined up and snapped a plate tightening it down.

Hope that helps,
John

On Thu, 21 Sep 2023 07:29:34 -0400, yellow04 via Fot <fot at autox.team.net> wrote:

Joe,

If your gearbox has slowly started leaking around the adapter plate, in all likelihood the issue is the six bolts that hold the plate to the back of the gearbox have loosened up. If nobody safety wired them or didn't use any kind of threadlocker on them, this is typically the problem when leaks slowly start in this area. The likelihood of needing to replace the adapter plate is not all that high, assuming the leak is not huge and you have not been driving the car with copious amounts of oil leaking about.

The adapter plate is not part of the overdrive unit, so replacing only the adapter plate is not too difficult. Six nuts hold the OD unit to the adapter plate, remove the nuts from the 4 short studs first, then start working the nuts on the two long studs evenly, and spring pressure should separate the OD unit from the adapter plate. Pay attention to the 8 springs as you slide the OD unit off the mainshaft, when they fall out they like to roll under things. Place the OD unit aside, other that cleaning the gasket surface you will not be messing with that.

I use the little bottle of Permatex Aviation gasket sealer for gearboxs, seems to work well for me.

The six bolts that attach the adapter plate to the back of the gearbox case are now visible, if these bolts are not properly torqued you just found the source of your leak. Remove them, clean up your gasket surfaces and reseal. The same gasket is used here as the non-overdrive gearbox.  Rimmers sells bolts specifically for this application, they have threadlocker that is safe for the aluminum case on the threads. They have been working for me. These 6 bolts may be safety wired, always a good idea if you don't buy a set of new bolts from Rimmers. If you go the safety wire route, pay attention to the parts as it is easy to run the wire in such a way that it fouls when the OD unit is installed.

The last adapter plate I bought from Rimmers was embossed with "ORS", I believe it was made by Overdrive Repair Services, the business started by Laycock employees after Laycock closed their doors. I didn't really compare it to a Triumph adapter plate, but I can see how John Esposito might call it an upgraded adapter plate. If you need one, I'd just order it from Rimmers along with those 6 bolts. 

Assembling the OD unit back onto the gearbox is where the real fun is, you need to line up two sets of splines in the OD unit, compress the 8 springs and make sure you don't foul the oil pump plunger on the cam. Many ways to accomplish this, some are tedious, frustrating, and can completely drive you crazy. The easiest way I have found is to safety wire the pump plunger, install the pump drive cam and make sure it is pointing away from the pump, apply the sealant to the gasket and place in on the OD unit, align the splines in the OD unit, (a spare OD mainshaft is really helpful with this) and offer up the OD unit to the box. Slowly slide the unit on assuring everything is lined up until the gasket is almost touching the adapter plate. Then, install the nuts and washers on the long studs only a couple of turns. Then you slide the OD unit backwards WITHOUT TURNING the rear flange until it hits the nuts. Then you install the 8 springs in their correct position, (shorts go inboard, longs go outboard) by stuffing them onto their posts on the sliding member then levering the other end onto the nubs on the adapter plate. Take a really good look to make sure you have all 8 springs correctly installed, then tighten the nuts equally to draw the OD unit home. Then install the 4 nuts and washers on the short studs, remove the safety wire on the oil pump plunger, refill with oil and you are good to go.

If you run into problems or need to borrow a spare OD mainshaft to line up the splines in the OD unit, feel free to reach out!

Henry

On 2023-09-20 19:23, Joe Boruch via Fot wrote:

I have a leaky a-type OD in my street TR4 that looks like it's leaking from near the adapter plate.  I have never taken one apart.  Can I just separate the OD from the trans and replace the gaskets or the adapter plate (I've heard that Quantum Mechanics sells an uprated plate and am checking with John to see if he has one) and then reassemble without needing to take the OD apart further?  There is a youtube video that shows an OD being separated and it looks like it is do able.  Thoughts?  JoeB

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