your opinion of mitchell overdrive

AA Ford Discussion Group relating to the repair and restoration of your AA Ford.
birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

your opinion of mitchell overdrive

Post by birdacre » August 5th, 2017, 1:07 pm

is this a good match for a AA in your opinion? i have a four speed with a 5:17 ratio worm drive rear end. it was converted to 4 speed years ago. it is a dec. 28. how much more speed could be safely exprected? and how easy is it to install and what do they go for? any insight, experience appreciated. thank you, kevin

KimVanOrder
Posts: 464
Joined: August 11th, 2013, 4:25 pm
Body Type: 82-A Platform
Model Year: 1928
Location: Hamilton, Mich.

Re: your opinion of mitchell overdrive

Post by KimVanOrder » August 5th, 2017, 4:11 pm

birdacre wrote:
August 5th, 2017, 1:07 pm
is this a good match for a AA in your opinion? i have a four speed with a 5:17 ratio worm drive rear end. it was converted to 4 speed years ago. it is a dec. 28. how much more speed could be safely exprected? and how easy is it to install and what do they go for? any insight, experience appreciated. thank you, kevin
A four speed is no faster than a three speed. The top speed ratio on both is 1:1. In my opinion stay original. And look for the high speed worm instead. You have the same yr. and month as I do.. Top speed clocked of 28. and shaking like mad. :shock:
KVO
Dec. '28 AA

birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: your opinion of mitchell overdrive

Post by birdacre » August 5th, 2017, 6:13 pm

my truck is the high speed worm 5:17. do they make a mitchell for worm drive, i know a few years ago they didn't. any new products?

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » August 6th, 2017, 5:04 am

I recently took delivery on a Mitchell 36% overdrive, but have not installed it yes. VERY easy to install. I assembled it to a spare rebuilt rear. Next is to change assemblies with the one in the truck. I'll do that in the next week or so, if time permits. Very well built and the parts just go together without trouble. As soon as I get it going, I'll post back...

Frank

birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: your opinion of mitchell overdrive

Post by birdacre » August 6th, 2017, 7:33 am

is your truck a worm drive? did you buy it new? are used ever found? and finally what do they go for? thank you.

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » August 6th, 2017, 9:20 am

Yes, mine is the same worm ratio as yours. From what I understand, they have not made many to fit this rear. Call Mitchell, they can give you the latest price.

Frank

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1crosscut
Posts: 747
Joined: December 25th, 2010, 7:22 pm
Body Type: 82-A
Model Year: 1929
Location: Lincoln, NE

Re: your opinion of mitchell overdrive

Post by 1crosscut » August 6th, 2017, 10:15 am

Frank. I and I'm sure others will are quite interested in how this goes for you. Can you take pictures documenting the steps / process of the installation?
------------
Dave

birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: your opinion of mitchell overdrive

Post by birdacre » May 8th, 2018, 12:00 pm

what did you pay for your AA mitchell in your firetruck? hope all is well. kevin

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » May 9th, 2018, 5:41 am

Well, it's time to give a report. The installation in the chassis was as easy as it was on the bench. I raised it onto my lift and dropped the complete rear end assembly to the floor. I disconnected the rear axle at the springs and took out torque tube and radius rods with it. The new assembly went in easily. I find that the new splitter box is smooth shifting and I get about 45-50 mph on the flat. The truck needs to be shifted into Ford high (from Mitchell high) sooner than I would have thought, but that's OK. I don't remember if I said this before, but the only modification I had to make was in the shift mechanism. Mitchell supplies a cable shift that clamps to the Ford shift lever, but I did not like the looks of this set-up. Upon request, they sent me a couple of sample brackets that I could experiment with to fabricate my own design. This was necessary, since I have a rather large water pump between the Ford transmission and the middle cross member that connects to the final drive shaft and we both thought that fabrication on site was the best method. With this help, it was a simple process to make a rod/clevis arrangement that looks much better to me. Mitchell said they went to the cable shift because of some trucks jumping out of Mitchell high on bumpy rural roads due to being heavily sprung. I have not seen any of this with my truck, but then I stay on roads...
Attachments
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Installed Mitchell
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Pulling driveshaft from rear end
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Drive shaft coupling
IMG_4923.JPG (129.71 KiB) Viewed 1099 times

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » May 9th, 2018, 5:44 am

More photos
Attachments
IMG_5295.JPG
Transmission Bracket
IMG_5295.JPG (190.63 KiB) Viewed 1099 times
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Mitchell's cable
IMG_5293.JPG (207.23 KiB) Viewed 1099 times
IMG_5256.JPG
Front Shifter Rod/bracket
IMG_5256.JPG (199.46 KiB) Viewed 1099 times

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » May 9th, 2018, 5:45 am

More photos
Attachments
IMG_5294.JPG
Cabin View
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birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: your opinion of mitchell overdrive

Post by birdacre » May 9th, 2018, 6:03 am

what did you pay for your overdrive? also how hard was it to disconnect the springs from rear end. I see a large slotted machine bolt and a bolt that comes in from side. please update. kevin

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emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » May 9th, 2018, 6:10 am

If I remember correctly, I paid just under $3000. To remove the springs from the rear, I unbolted the saddle bracket on the axle tube and left the springs on the frame.
Attachments
IMG_5252a.jpg
IMG_5252a.jpg (171.36 KiB) Viewed 1092 times

birdacre
Posts: 390
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: your opinion of mitchell overdrive

Post by birdacre » May 9th, 2018, 11:19 am

thank you for the input. it looks quite simple. I thought I had to try to pull the pin with the set screw. I will keep you posted. hey one more question. I have a four speed in my 28. it was switched years ago. I took it apart and made 1 good transmission from 3. all gears and clusters in VG shape. it has developed a railing noise in 4th. not the typical whine but a railing noise. both input and output shaft bearings were new. I wonder if mix and match gears start to sing after a bit. have about 200 miles on truck since reassemble. I am thinking about the Mitchell for road speed. do you think I would still have power if using the truck for a load of lumber etc. can you lock out the Mitchell and have it like it was or is it a totally different mix now. thank you, kevin

User avatar
emf
Posts: 65
Joined: March 21st, 2016, 5:21 am
Body Type: Firetruck
Model Year: 1928
Location: Hudson, NY

Re: your opinion of mitchell overdrive

Post by emf » May 9th, 2018, 1:27 pm

The Mitchell is called a gear splitter not an 'overdrive' by the manufacturer. You would have with a 4 speed in front, essentially 8 forward gears and 2 reverse gears. You can shift into 'Mitchell' with the Ford transmission in any gear you like. So, yes, you can leave the Mitchell in low range and ignore it.

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