Mitchell Overdrive problem

[Del in NE Ohio]

This past Fall I installed a Mitchell O/D for a local club member. Routine install. Noticed immediately that O/D would drop out of high range and into neutral when coasting in gear. Contacted Mitchell. Steve’s diagnosis was bad synchronizer. I removed unit and shipped it back to CA for repair. I received the repaired O/D last Thursday. Finished install and did test drive today. Problem is still present. Has anyone else had this problem? If so, how did you address it?

[nkaminar]

Del,

I had the same problem. It turned out that my linkage was not allowing the drive to fully engage. Check your linkage. One way to check would be to disconnect the linkage, put the drive in high range directly at the unit, and then take a drive. I solved my problem by adjusting the linkage.

[larrys40]

Del
I agree sounds like I’d make sure linkage is ok as suggested above , also, if rear engine mounts are bad or loose it could cause the engine and trans to move more then it should and cause the overdrive lever and linkage to disengage..... especially if linage isn’t fully engaged if out of adjustment.
Larry Shepard

[Y-Blockhead]

Ensure you get it all the way into gear when shifting to high. When I first got my Mitchell I "missed" a few gears. Totally my fault, I simply was not shifting it hard enough (being too gentle) to get it all the way in gear.

Not sure if I agree with the loose engine mounts being a problem. The trans, engine and driveline all move as a unit. The shifter is mounted to the trans.

One thing I do remember from the instructions was to ensure the lever that connects to the shifter be straight up and down, not at an angle. Adjust with the splines on the shifter.

[Tom Endy]

We had the same problem last summer with several installs. We had to ship two back to Mitchell for repair. The third one over time corrected itself. According to Steve Mitchell a new supplier of the synchro gears did a poor job of manufacturing and got what looked like weld splatter on the gears that prevented then from fully engaging. My understanding is the problem has been corrected. We did another install a week ago with a recent delivered overdrive and it is working properly.

Tom Endy

[GeneBob]

Sponsored Links (Register now to hide all advertisements)

I have a Ryan overdrive and it has a detent that can be adjusted on the overdrive unit. When I first installed the overdrive it would occasionally fall out of overdrive so I tightened the detent and that solved it. I don't know if the Mitchell has a similar arrangement.

[larrys40]

YBlockhead
I’ve installed quite a few Mitchell’s and have seen poor engine mounts cause trans and engine to move which in fact can cause the shift mechanism to shake. Noting Tom Endy’s issue I would think the issue has been covered by Steve Mitchell . He is always very responsive.
Wether you agree or not poor mounts can cause lots of different issues. Worn and sagging pressing on the brake pedal can actually cause the torque tube to rest on the brake cross shaft . I do service and restoration by occupation so have seen quite a bit . Also, as was said the Mitchell shifts hard sometimes when new and you must ensure that it is fully engaged. Sometimes the linkage needs a little adjustment as well.
Just sharing what I’ve seen and know .... I’ve dealt with my fair share of them.
We are lucky to have the Mitchell overdrive as an option to us. Special thanks to the Mitchell’s.
Larry

[Y-Blockhead]

Originally Posted by larrys40

YBlockhead
I’ve installed quite a few Mitchell’s and have seen poor engine mounts cause trans and engine to move which in fact can cause the shift mechanism to shake.
Larry

Haha, If your engine and trans is shaking enough to shift your Mitchell out of gear I would says you have some REAL issues...

[Del in NE Ohio]

Thanks all for your responses. I’ve installed 6–7 of these in recent years and never had this issue. Will focus on linkage. I remember the instructions making mention of the shift lever being installed in a vertical configuration. Would that be with the unit in low range?

[Bryan Thompson]

Disconnect the shift lever from the unit.
Hit the shift mechanism on the unit with a hammer. Driving it in.
If it still pops out it is the unit, not the linkage.
These were Steve's directions.

[Y-Blockhead]

Originally Posted by Del in NE Ohio

I remember the instructions making mention of the shift lever being installed in a vertical configuration. Would that be with the unit in low range?

That would be in neutral position per the instructions.

"When adjusting shifting linkage, put overdrive in neutral. Aluminum shift arm should be straight (vertical)."

[Bryan Thompson]

High gear is with shift rod in, shift lever forward.
Low gear is with shift rod out, shift lever rear.
Neutral is in between.

[SteveE]

Any ideas besides fabricating new parts or cutting my frame to make this Mitchell OD work without interference? Thinking a rod with a U shaped channel to clear the frame and battery box or a longer shifter pivot arm linking the rod to the OD.

Running a '39 synchro top loader tranny while I rebuild my '30 tranny. The aftermarket Model A frame (I think aftermarket) appears to not match the Mitchell design. I cut off the left "rabbit ear" on the '39 tranny (two ears on the output near the U joint used for trucks in the day).

Issues:
Mitchell OD shift lever interference with '39 shift lever and Mitchell OD shift pivot arm and
OD shifter rod and arm cannot clear the frame nor the battery box.

[GeneBob]

Although I have a Ryan overdrive, I have the Mitchell shifter and brackets. I am running a 1935 transmission which had the same interference issues. I modified the u-joint clamshell in a similar way to clear the parking brake rods. The Ryan mounts at the rear of the driveshaft tube. I had to adjust the shifting rod to the longest length I could in order to clear the shifter crank on the driver's side. I also had to cluge a hold down for the bracket since the bolt pattern on the bracket is made for the Model A transmission top. As far as shifter stick interference, I shortened the OD shifter and rotated it back until the two cleared each other. My OD shifter is pretty far back when not in OD.
Because the trans is not the Model A trans, I didn't mind making these modifications in order to fit it all together. You might also try bending the OD shifter rod to put an angle at the end near the shifter crank in order to clear the frame.
It was a tight fit to adjust, bend and grind everything to fit on the side of the trans.
Added: I also had to sand/grind some clearance into the underside of the floorboard for the bracket because it would thump under acceleration.

[SteveE]

Thanks for the ideas. I'll take a good look at shortening the OD shifter. Or maybe I can get an older A shifter and weld the 39 top-loader adapter to the bottom. I think the OD arm is brittle as it doesn't look like aluminum or steel. May be pot metal. Appreciate the ideas.

[GPierce]

Get the Mitchell cable shifter.

[SteveE]

Steve at Mitchell Mfg called and solved the problem. I can fab an extension arm and they sell them for the '28 Model A. Then, heat the shifter and bed it so there is no interference.