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your opinion of mitchell overdrive

Posted: August 5th, 2017, 1:07 pm
by birdacre
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

Re: your opinion of mitchell overdrive

Posted: August 5th, 2017, 4:11 pm
by KimVanOrder
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:

Re: your opinion of mitchell overdrive

Posted: August 5th, 2017, 6:13 pm
by birdacre
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?

Re: your opinion of mitchell overdrive

Posted: August 6th, 2017, 5:04 am
by emf
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

Re: your opinion of mitchell overdrive

Posted: August 6th, 2017, 7:33 am
by birdacre
is your truck a worm drive? did you buy it new? are used ever found? and finally what do they go for? thank you.

Re: your opinion of mitchell overdrive

Posted: August 6th, 2017, 9:20 am
by emf
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

Re: your opinion of mitchell overdrive

Posted: August 6th, 2017, 10:15 am
by 1crosscut
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?

Re: your opinion of mitchell overdrive

Posted: May 8th, 2018, 12:00 pm
by birdacre
what did you pay for your AA mitchell in your firetruck? hope all is well. kevin

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 5:41 am
by emf
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...

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 5:44 am
by emf
More photos

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 5:45 am
by emf
More photos

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 6:03 am
by birdacre
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

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 6:10 am
by emf
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.

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 11:19 am
by birdacre
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

Re: your opinion of mitchell overdrive

Posted: May 9th, 2018, 1:27 pm
by emf
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.