Mitchell Overdrive

[Steve Rinaldo]

I am doing a service on my "A" and can not find any maintenance information about the unit. Is there any thing that needs to done other than check the oil level, like hidden grease fittings? Thanks, Steve

[divcoone]

Steve, look at drive shaft. You will see a plug. Remove the plug and you will see a pipe plug. Remove that plug and thread a long grease nipple in its place.

[Jack Shaft]

I found out the hard way Mitchell's like to be shifted aggressively.@2500 a pop, change the oil, its cheap insurance

[Kinner]

Steve mentioned to me on oil change in his overdrive and syncro transmission to use 25% STP. I have not changed oil yet but will try it when the time comes.

[nkaminar]

I emailed Mitchell to see what oil they recommended for their overdrive and synchro transmission. They wrote back:

"Our preferred oil is a good 85/140 petroleum based gear oil with a GL5 rating.
Each unit will take approximately 1 quart of oil. Could be slightly more or less."…

[Y-Blockhead]

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Originally Posted by divcoone

Steve, look at drive shaft. You will see a plug. Remove the plug and you will see a pipe plug. Remove that plug and thread a long grease nipple in its place.

Actually on the latter units there is a grease fitting on the rear drive shaft also.

Originally Posted by Kinner

Steve mentioned to me on oil change in his overdrive and syncro transmission to use 25% STP. I have not changed oil yet but will try it when the time comes.

The instruction sheet that came with my Mitchell states "High quality 85/140 weight petroleum based gear oil with a GL5 rating."

[C1Nelson]

On most GL5 oil bottles it states not to be used in manual transmissions. I think because the GL5 formula is corrosive to the synchros. Is this only the older transmissions? Any thoughts ?

[nkaminar]

If the GL5 rating bothers you, you can use the oil with the GL4 rating, which does not attack brass.

[emf]

Originally Posted by divcoone

Steve, look at drive shaft. You will see a plug. Remove the plug and you will see a pipe plug. Remove that plug and thread a long grease nipple in its place.

Be sure to remove the long grease fitting after...


Frank

[Dale'45]

85-140 is too stiff in mine during cool weather. Replaced with 80-90weight and it shifts much easier. Dale

[Synchro909]

Originally Posted by Dale'45

85-140 is too stiff in mine during cool weather. Replaced with 80-90weight and it shifts much easier. Dale

Ditto.
As for GL5 being corrosive to bronze (not brass), if it is, Mitchell will have HUGE warranty claims and I don't think they're so stupid as to make a recommendation that would damage their units like that.
The first O/D unit I got has no grease fittings for either drive shaft. They came later and the recommendation was for a good quality synthetic gear oil.

[Chris in WNC]

(deleted)

[Y-Blockhead]

In the paperwork I received with my Mitchell O/D it states "Change gear oil once a year or every 5,000 miles. Use 85w/140 petroleum based gear oil with a GL5 rating.

[Lawrie]

I don,t know about the GL5 attacking the bronze parts, all my V8s use the 85/140 in the trans and rear axle, the 33 has about 90,000 miles on it with the current transmission, it still shifts beautifully , never any bronze in the oil at changes,
I tied the 85 GL 4 for small Jap light duty trucks and manual trans, cars, it was noisy and as thin as p--s
Lawrie

[daveymc29]

After a whole bunch of miles and three engines I took the Mitchell up to their shop in Calusa and had them take it apart and replace as needed the worn or broken parts. Steve gave me a bronze looking sycronyzer that to his eye showed the beginnings of some wear. It had been in my car at least 30K miles and that was the extent of the wear. He has the proper machinery to open the case and remove everything, then after cleaning and inspection put it back together. I had to leave it with them as they were short handed or he could have done it while I went to lunch. I used the 85/140 oil they recomended and changed when I had about three thousand miles on the oil. Better do that now, cause I'm surely there by now. Good service and I don't remember the cost, not high enough to remember.

[Synchro909]

Originally Posted by daveymc29

After a whole bunch of miles and three engines I took the Mitchell up to their shop in Calusa and had them take it apart and replace as needed the worn or broken parts. Steve gave me a bronze looking sycronyzer that to his eye showed the beginnings of some wear. It had been in my car at least 30K miles and that was the extent of the wear. He has the proper machinery to open the case and remove everything, then after cleaning and inspection put it back together. I had to leave it with them as they were short handed or he could have done it while I went to lunch. I used the 85/140 oil they recomended and changed when I had about three thousand miles on the oil. Better do that now, cause I'm surely there by now. Good service and I don't remember the cost, not high enough to remember.

You guys are lucky to be able to do that. For us, by the time we pay freight each way, then pay for the work, we might as well just buy a new one.
I'd like for the to have a look over my 70,000 mile O/D. Oil changed at 5,000 miles throughout.

[rotorwrench]

Transmissions with phosphor bronze bushings and babbitt thrust washers are susceptible to deterioration under a high EP rated oil. Brass will be affected over a longer period of time. The Borg Warner Overdrive transmissions also have a sprag type overrunning clutch as well as the transmission parts that are affected by high EP so they always recommended mild EP such as GL3 or the later GL4. If soft metals are not in a transmission or rear axle then high EP GL-5 is not an issue. If Mitchell recommends GL5 then use that.

[John Borland]

Originally Posted by divcoone

Steve, look at drive shaft. You will see a plug. Remove the plug and you will see a pipe plug. Remove that plug and thread a long grease nipple in its place.

I need to purchase the long grease nipple for greasing my Mitchell driveline. Hopefully, one of you folks can tell me the size of this fitting.

[Y-Blockhead]

You should have received the Special grease fitting and Allen wrench with your Mitchell. Not sure where you could get one like that. You might contact Mitchell? [email protected]

You might also be able to use a rubber tipped grease fitting

[Tom Endy]

Only the later Mitchell overdrives have these grease fittings. The only lubrication on the older ones is the gear oil that you need to change periodically. The two grease fittings on the later ones grease the two spline couplers.

Tom Endy