Borg Warner OD vs Mitchell OD weight?

[AzBob]

Thinking about replacing my BW overdrive with a Mitchell. Does anyone know if the Mitchell is lighter weight than the BW? Mitchell has aluminum case, BW all cast iron.

[Hitman]

It's probably a wash between the two units.

More importantly, you want to make sure the location of the overdrive is contributing less to the unsprung weight of the rear end. Mitchell's are in the middle of the torque tube, about as far forward as they can go without interfering with the body (excluding the slant version). BW's can be placed there too, but some have been mounted closer to the rear axle.

[Gene F]

Why replace it ?

[AzBob]

Originally Posted by Gene F

Why replace it ?

1. Geared too high (33%) Not very practical in the mountainous area where I reside.
2. Wear in the lock out mechanism is causing the BW to pop out of direct drive during deceleration.
3. All the electrical wiring, solenoid, relay and switches goes away with the Mitchell.
4. If the Mitchell is lighter, less unsprung weight. So far no one has been able to confirm if the Mitchell is indeed lighter.

The only negative with the Mitchell, is the shifter takes up floor space and imo does not look very pleasing. Yes, I know one can opt for cable shifting just don't think the cable would be as easy to shift as the lever.

[rotorwrench]

The BW overdrive has the shafting that goes straight through but does have the larger diameter shafting due to the planetary set and the freewheeling drum. I think they used the smaller R10 housing for most conversions so they are relatively short. I think Studebaker, Nash, and Willys used those. The Ford ones are a bit longer in the tail. The solenoid and governor are there but don't add a lot of weight. All the R10s have the same basic step in ratio.

The Mitchel has the aluminum case but it is larger and fairly robust to be able to support the two shaft system. It has a main shaft and counter shaft much like regular manual transmission. There is an input gear shaft and an output gear shaft with the synchroniser between the two. The cluster gear runs on the counter shaft. The unit has a fairly heavy duty shift fork assembly to effect the gear change.

If one is heavier than the other then it wouldn't be by much.


The OP mentions that his BW overdrive is sometimes forced out of direct drive during deceleration due to wear in the lock out mechanism. While I've not operated the model A conversions, I do have a lot of miles on both my Mercury cars. I've never experience a drop out of lockout. The way the lever engages the lock out rod, it remains in place pretty well even though the control rod is spring loaded. There must be some pretty heavy wear in either the rod or the end of the lever in there. The one warning than is in the 1949 through 1951 Lincoln-Mercury Overhaul Manual is that the car should not be operated in 2nd and overdrive for too long. I guess it makes the planetary spin too fast under sustained use. There is nothing in the troubleshooting info about problems with direct drive. When we used to take our original family car on trips to Colorado, coming down those mountain passes required a lot of use in direct drive. It was actually more common to have the overdrive unit lock up when it failed. I've know two people that have had high speed lock up and it scared the hell out of them. Needless to say, their planetary unit was shredded.

Since the model A conversion doesn't have the reverse lockout mechanism, it must be getting more wear due to constant cable pull operation in order to reverse the car. That action doesn't affect the cable pull in an overdrive transmission car since all the lockout action comes from the shift mechanism in the transmission section.

[AzBob]

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Thanks for the info Rotorwrench. My BW od is an R10B-1R. From what I can gather, it is out of a Ford. When I purchased the car, the od lockout cable was not adjusted properly and allowed the lockout to easily pop out of engagement just driving on level road. I have since rectified the cable adjustment but it still pops out upon deceleration.

As per Hitman, the weights between the BW and Mitchell are probably a wash.

[Dodge]

The borgwarner overdrives were great in their day. They still work well today and
there are still parts around for them. I have had 3 Model A's with them in them and
liked them. All that said once you put in a Mitchell you'll never look back.
They are much easier to use and that lever becomes natural after a while. The cable shift is a little harder to use. I've never weighed either but it seems that the Mitchell might be a little lighter.
There is probably still a market out there for your borgwarner to help offset some of the cost of the Mitchell.
One other thing is when you shift the borgwarner into overdrive it is a bigger jump and
slows the motor down quite a bit more. The Mitchell when shifted into overdrive seems like a very natural transition with it feeling like a normal shift into a fourth gear.

[Keith True]

I had a BW in my pickup for a while.I took it out.It wasn't the quality,or design,it was just the fact that it was a little too high for my usage.It was great on the highway though.Another thing I didn't like about that particular one was the cable shift.There is no way to shift with a push-pull cable like you can with a switch.The two cables mounted to the steering column bracket.It worked nicely,just slow.