I have an overdrive trans to install in my 68 122. From all apperances it is an m41 with a J overdrive. The tag on the trans says M40G. It is out of a 73 140 but it may not have been original to that car. The trans looks healthy inside so I would like to install this to evaluate the overdrive. Later overdrives I have worked with had drain and fill plugs. This unit does not. I would like to know any info about this anyone want to offer in general. I need to know what the recomended fluid is and capacity. Where can I find info on repairs to this OD unit? Is the info on IPD's site applicable to earlier OD units?

Another difference is the speedo cable attachment. On my car I have a cable with a nut to hold it onto the speedo driven gear. On the OD unit the cable end is held in with a flat retainer and a small bolt....no nut on the cable. How can this be addressed?

Thanks
Chris

BTW, looking for 140 auto drivesshafts will usually end you up with mis-matched u-joint sizes, hence my auction of a 123gt shaft on ebay last month. Yes, it may not be as strong as converting everything, but it works as a bolt in.

Chris,
Before you install the tranny, remove the OD (no matter what type) and replace the following.

At minimmum: the two actuating pistons and O-rings. This task is SO much easier with the transmission out of the vehicle. If it is a J type the rest of the O-rings can be done with the OD unit in the vehicle. But at about $50 for a gasket and O-ring set, why not just do a mini rebuild first?

It would be wise to also separate the cases and replace the two gaskets between the cases and brake ring in the middle of the OD. To replace the front gasket, the brake ring needs to be removed. To remove the brake ring the OD needs to be off the tranny to access the nuts that hold the bars that the actuating pistons push on to put the OD into OD mode. Again, the OD is not easy to remove from the tranny while in the vehicle.

And since it is this far apart, the simple spinning of the bearings and what have you should indicate if any of them will need replacing. Which if you found out while the OD was in the vehicle would require removal of the OD from the tranny which while in the vehicle is not an easy task.

Does anyone see a pattern developing about not putting the OD and tranny in before working on the OD besides me???grin??

AS you separate the cases, do not let the planetary gears fall out of their carrier, mis-alignment upon re-assembly will cause noise. If they do align the dots to the sun gear if they have the dots. Some early J's did not.

Fluid, 80W-90 gear lube. Somewhere around 1 3/4 qts.

Speedo cable: ????the nut at the instrument cluster should be the same for all models???? of that vintage. (Neck elongated for chopping off.) Possibly get the cable from the vehicle you got the tranny/OD from if it is long enough???

If you e-mail me direct, I have diagrams and instruction sheets that might be of assistance with the OD.

Duane

...I've been saying that for years. If it's good enough for Irv, it's good enough for me.

I thought all the ODs were on M41 trans. But I could be wrong. I'm doing the exact same thing to my '68 122 (only with a D tyoe OD) so I can assure you will need a longer speedo cable (they're reasonably priced at IPD) and the front part of the drive shaft will have to be shorter. You can either get one from a 140 automatic (there's one for sale on ebay right now) or have the front part of your 122 shaft shortened at a machine shop.
Anyway I have been recieving mountains of help from Duane Hoberg. It might be worth your while to contact him with your questions about the OD.


ODGuru@kc.rr.com

To a large degree, you are correct...but, J-type and D-dipe ODs are not the same length. An auto driveshaft should work with a D overdrive, but not necessarily a J-type.

Also, them long speedo cables aren't as easy to find as you might think. Unless I'm missing something... Granted, easy for a '73 or later speedo, but for the early scew-on speedos, it's getting tough. I still havn't found one for my hot rod 145.... though I can't say I've looked too hard.

And yes, from what I've seen, Duane is indeed the ODGuru... and rightly so. I've never followed his good advice though... I just slap 'em in there and see what happens. So far, I'm three for three. I'd be more cautious of the D-tipe overdrives. Experience and intuition tells me they are more problematic.

Sorry about my spelling of "tipe"... It's a moral and religious thing. "D-type" is reserved for my second favorite Jaguar. My favorite being the C-type, aka XK120C

-Matt

Hmmmm... I've got a J and a D that interchange just fine, so some of them are the same length. I have heard that there is a different length -- I think the difference is in the adapter between the gearbox and OD -- but I've never seen a side-by-side comparison.

OK...I'll go along with that... My measurements were from the front of the gearbox (where the bellhousing attaches) to the back of the driveshaft flange.

The difference is only a quarter inch, and some driveshafts might be able to pick up that slack in the splines. But not necessarily all of them. I doubt the spacers between the OD and tranny are interchangeable Some are aluminium, some iron...though maybe they do interchange. but...heck, I don't even know if the output shafts of the transmissions would work from one to the other....????

In any case, I'd bet that y'alls interchange between J and D tipe overdrives only worked because you had enough slack in the driveshafts to take up the difference in length...

For that matter, I only measured those out of curiosity based on Sutherland's experience with his originally automatic converted to OD car... and someone might well have messed up the driveshaft measurement in the first place with his car....?

I've torn apart several M41s, but I've only put one back together, so my knowledge is a bit limited in this regard..

-Matt

I've used the same driveline on a D and a J in the same car no problem.