What is the average life span in terms of mileage for the M-46 OD unit before it has to be rebuilt?

Depends upon your definition of rebuild. O-rings and gaskets seem to last in the range of 130,000 to 250,000, depending upon outside temperature range. The wider and colder the swing, the sooner the O-rings need attention.

Other major parts can outlast the rest of the vehicle. Depends upon owner care. By keep the fluid level up and clean and correcting minor problems promptly, the bearings and other moving parts should never need replacement.

Duane

My 81 M46 shifts into OD OK, but there's a very slight shudder and a slight hesitation. What would be the most logical sequence of things to repair/clean to achieve clean precise shifts?
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock; 86 240, 130K

Two areas: the hesitation could be due to a loose or dirty connection at the solenoid.

Most likely the actuating pistons are starting to fail. Instead of a smooth pressure build up with tight O-rings, at low pressures some fluid initially blows past the O-rings until a higher pressure is reached which forces the O-ring tight. The shudder is the cone slipping and grabbing the brake ring as the pressure builds.

Time to plan for three to five hours under the vehicle.

Duane

Can you recommend where to buy the repair kit? I want to do this job with high-quality parts. Any ideas on cost?

Is this a terribly difficult job for an organized but only moderately experienced do-it-yourselfer? I go really slowly, but, I've managed to do four or five brake jobs, injector seals, new breather box on a K-jet, wheel bearings, a couple of timing belt jobs with three front seals, water pumps, transmission services and flushes, a power steering flush, a clutch once on a Datsun, and many many years ago, a couple of engine overhauls on VW's, and a bunch of really easy stuff on a variety of cars. Looking at the pictures of the overdrive unit in pieces, it looks like it might be more complicated than any of the jobs I've ever tackled. How difficult is it?

Good time to thank the Brickboard for all the help I've received over the last six months on most of these jobs. I would be lost without the help from the Board. Believe me, I really appreciate all the friendly help I have received.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 240, 130K

IPD carries a kit as well as I do.

It is similar to changing a clutch BUT you do not have to lift a 150 lb tranny, just remove the rear portion leaving the tranny in the vehicle.

Although there are quite a few parts in the OD, you are concerned with just a few in the front and a few accessable via plugs which are under the sump cover.

On the Brickboard Features pull down, go to 700/900 FAQs and go to the index. go to the section on OD rebuild and see what is involved.

Duane

Seems like it depends on whether or not the previous owners used their clutch or not when engaging it. (see my post on M46 poll below) Mine's got 238K miles on it. PO told me they used the clutch.
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Bob W.
'91 744T 173K
'82 245Ti 238K
'81 245 GLT, non-turbo 275K
'67 122 wagon