Foci final drive

I found out on another forum that all Zetecs come with a 3.82 final drive. Booo! After that, I found the 4.06 final drive for the foci for like $140. This sounds very worth it to me. Anyone done that conversion? How much difference did it make? Also, how much of a bizzatch is it to install once the trans is out?

Thanks,
Ben

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Ben Hetland
1973 Volvo 142 project car (with some cone-smashing on dirt in it's future, however)

"No. Rally Racing is a back alley sport filled with jackals, headhunters and thugs!"
-Pops Racer (Speed Racer movie)

www.utahrallygroup.com

1fastben Wrote:
-------------------------------------------------------
> I found out on another forum that all Zetecs come
> with a 3.82 final drive. Booo! After that, I found
> the 4.06 final drive for the foci for like $140.
> This sounds very worth it to me. Anyone done that
> conversion? How much difference did it make? Also,
> how much of a bizzatch is it to install once the
> trans is out?
>
> Thanks,
> Ben

Ben think of all gears as levers arrayed in a circle. We're 'spossed to write the ratios like 4.06:1 so the lever ratio is clear 4.06 TO one.

Trying to finger out what sorta change it would bring, substituting a bigger lever for a short one is easy division. You'd be just 6.28% shorter geared, and NOT WORTH IT. Granted your tires have doubtless geared ya UP that much at least so yeah youse could be back where a stock car is but dammit you gonna yard the trannie and have er open then find something usefull shroter, something that would at least leave you 20% shorter than stock taking tire overall diameter into account.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
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is 3 hours behind Eastern Standard Time.

I have one in my transmission. It made a slight difference, but it is mainly noticible in slightly different RPMs at certain speeds. Not going to make the car a rocket ship out of the corners. No one makes an alternative final drive other than quaife and they require you run their gear set $$$$.

Disassembling and Reassembling that trans requires no special tools other than a set of c-clip pliers, some sockets 10mm and 13mm if memory serves me, and prybar.

You will need a shop press or be able to pay someone to pull all of the gears and syncros off of your old output shaft and put them back onto the new one. You will also need a new bearing from Ford for one end of the output shaft since there is not a good way to remove this bearing without damaging it. I think it was like $10-15 from Ford. Ford made at least two different bearing types for that end so if depending on which one you get from the parts guy you may have to change the race in the transmission, it will still run a couple of rallies with the wrong race which speaks to the durability of these boxes. It cost me about $125 to have a shop swap the gears for for me. Since my press did not have a wide enough opening to do it.

Technically you should buy a special tool from Ford to measure the bearing preload on the new ouput shaft and then shim the bearing races in the case to match. I did not do this in my trans and it has been working fine. The tool costs about $70 and require a 1-2 month lead time if bought new from Rotunda(The specialty tool maker for Ford). I can look up the number if you are interested.

The ring gear is a very tight fit in the dif. The recommended procedure is to put the diff in the freezer and the ring gear in the oven and then quickly assemble them. I did not do this and was still able to get the ring gear on but it was a pain. Make sure to locktite and torque the diff bolts properly. I found out the hardway what happens when you don't. The good news is that transmission will go a quite a ways with very little fluid and hole in the case. I drove about 50 miles on mine and the parts have held up file for the 3 rallies I ran after getting a new case.

From reading other transmission build threads I would say the MTX-75 is very easy to work on. You just need to be careful and have a couple of special tools if you want it done to the letter of the manual.



Edited 1 time(s). Last edit at 12/16/2008 09:35AM by Andrew_Frick.