...general question.Do we all understand what can and cannot be done,and why,on final drive ratio changes on a MTX75,using stoc Ford parts?
Thought I'd ask as it may merit a few words etc???

Terry
I will admit I notice several members have Focus final drive gear, why is this?taller or shorter?

Terry when I get my bankroll back up Ill be wanting to look for this option, or a different gear set that works better with the new oval 3L. 1st gear isnt completely useless (good way to make smoke) but its not terribly worthwhile ether. I find myself pulling out more in 2nd now than 1st. The drivetrain is unforgiving in this area. If I am driving mildly aggressive, I never touch 1st, just because because if your not dead nuts on with your clutch engagement, bucking ensues. I also have a 18" wheel/tire combo, and according to Dominic IIRC, the larger circumference combo makes up about the same difference as the taller 1st gear.

The focus has the taller first gear correct? is the whole focus gearset taller?

Adam

Stock V6 FDR is 4.02:1. 4cyl and "Euro" FDR is 3.83:1. The reason I changed mine was to lower the revs in 5th gear on the highway. It drops about 500rpm in 5th.

...OK,lets cover the 'basics' first.
We all need to understand that a higher final drive ratio (FDR) has a lower number.For example, a 3.8:1 FDR is a higher ratio than a 4.06:1...Think of the gears...1st gear has higher numbers than 4th gear.I know it sounds back to front but that is the way it is defined.
Most owners go for a higher FDR in say a 3.0 because the engine has more power etc and does not need the low,4.06,ratio to get the car moving.
Other point to note.The MTX75 is a FWD trans ....the position of the diff ring gear is fixed in the case,as is the output pinion/shaft that drives it.If the FDR is changed then you have to change TWO gears,the crown wheel AND the pinion.In a RWD the ratio can,on some axles,be changed by just the ring gear...as we can 'move' the pinion in the case...not so in a FWD.
Thank again of 'HOW' the ratio change affect the size(diameter and number of teeth) of the gears.A higher ratio(smaller number!) will have a bigger(more teeth/bigger diameter)pinion(driver) than a low ratio FDR....To match it,as its'bigger' we need a smaller ring gear with smaller diameter and less teeth.....do we understand that part so far?

….lets assume you all ‘get it’ so far.That covers the why part,now a bit of history and the ‘how’.
Most all FDR changes,using Ford stoc parts,centre around the ‘will it fit’ part.This takes us to a bit of history of parts and ‘design levels’.of the output shaft,the part that has the smaller ‘pinion’ gear.There are two levels of output shaft early( two piece) from ‘95> ‘around’ 2000 and ‘around’ 2000 up and late (three piece) from ‘around’ 200 up.I uses the term ‘around’ because there was no ‘firm’ change point on shaft levels…as I have said the ‘assy number’ on the tag on an MTX75 means NOTHING when it comes to the internal componet levels.I have seen early output shafts in 2002 MTX’s and late output shafts in 98 MTX’s….! Most of this was the result of ‘line trial’ transmissions that should have had early level parts be were built with ‘some’ later level parts as a trial by Ford…confused yet??? On some late level MTX’s they ‘used up early level parts on late model transmissions…Oh the fun!!
So how can you tell what you have?...Well you need an experienced eye when you strip down the trans to establish what level of output shaft you have first.This will decide costs etc of parts to change the ratio.
Now a bit of history.The early level output shafts (2 piece) had a pinion that was splined onto the shaft…so to change the ratio from say a 4.06 to a 3.8 all you needed was the Ford parts,pinion and ring gear at 3.80…off you go to Ford wath around $150 and buy the parts,swap over the the other bits from you old shaft and you are set…Great!


Now Ford will mess you up!.....The early level shafts are now…obsolete!....Can’t buy say a 4 cyl Zetec output shaft at the early level with a splined pinion…Only way you can get it…if you need it…is to buy an early Zetec used trans….a bit more than $150 eh!!!


So what of the ‘late’ level output shafts?..Why not use one of those in place of the early type?...Not so fast buddy!! The ‘later’ level output shaft has the pinion machined as part of the shaft,not a splined on part..’So what?’…Well Number 1,the shaft isn’t the same overall length as the early type and does not use the same level bearings…’Well change the bearings too…Yep,that would do it but….the cases are not machined exactly the same so the shimming of the new shaft bearings is not straight forward……BUT this is only a small part of the problem.Along with the new output shaft design you will also need anew INPUT SHAFT to match it….plus the fact you will need extra gears and other levels of syncro hubs to match it…and another reverse idler gear…Do we start to get the picture of what it takes to fit a late level output shaft in place of an early level…the early level we can no longer get!...ll in all it will cost around $500+ in parts alone to do an FDR change on a trans with early level output shaft….

But what if I have a ‘late’ level shaft already and want to change the ratio?

No problem,just get the correct level shaft and ring gear,swap all the parts from the old part to the new and it’s done….for under $200 of parts…


See guys,not so easy is it…Plus you would want to change any worn blockers,syncro hubs,roller bearings etc etc along the way….Does this help explain why work on the MTX trans is expensive…you pay for what shops like mine ‘know’ about the MTX75 and I can assure you we know ‘A LOT’ about this kogbox.What can and cannot be mixed and matched etc.I won’t get into changes in gear ‘cuts’,ratios within gears etc etc….THAT would be a whole chapter in itself!

Enough to say that we,HMS Inc,over many years work on all types of MTX75 ,have a very comprehensive parts ‘matrix’ that tells us what works with what…years of data and experience on this subject.

Below are the two output shafts.Early on the left,later on the right.

 early_output_shaft.JPG ( 578.18K ) Number of downloads: 74
 late_output_shaft.JPG ( 537.35K ) Number of downloads: 61



..Questions,comments??....Not a normal job for the DIY guy!!!

It sure ain't! Thanks, Terry, for taking the time to go through this with me last Summer. You saved me from making the mistake of asking a transmission shop to do the impossible: change the FDR with only the ring gear. D'oh!

In hindsight, even though changing the FDR on late model transmissions is more costly, it would have been a worthwhile conversion for my application. The turbocharged 3.0 is a bit too rev happy for fuel-efficient driving, but the turbo spools faster with the stock FDR. How do the trap times of turbo'ed 'Tour owners with the higher FDR compare to those with the lower FDR?

This post has been edited by gamiller: Nov 5 2007, 02:40 PM

even though changing the FDR on late model transmissions is more costly,


...if you have the 'later' 3 piece output shaft the parts are under $200...the early 2 piece is the one that more expensive to conver.Problem,as I said,is that some early MTX's had line trial late output shafts and some later MTX's had the 'hangover' early level shafts($$ to convert)...Only by inspection can you tell what is in your trans.

I'm sorry, Terry, but I read this over again, and I still don't get it.

You say the early shaft has a splined pinion gear which along with the ring gear can be replaced for $150 in parts.

Next you say that the pinion gear on the late shaft is not splined, so almost all the internals must be swapped out, costing about $500 in parts.

Lastly you say that for $200 in parts, the late shaft can be made to work, and it's the only option for most anyway since the early shaft is no longer available new.

What did I miss between the latter two statements?!?

This post has been edited by gamiller: Aug 11 2008, 08:31 PM

You say the early shaft has a splined pinion gear which along with the ring gear can be replaced for $150 in parts.


..the are now the obsolete parts that are no longer made so the cost is moot(unless you buy a used 95>97 Zetec trans)

Next you say that the pinion gear on the late shaft is not splined, so almost all the internals must be swapped out, costing about $500 in parts.


...yes but only if you have the early shaft in your current trans.




Lastly you say that for $200 in parts, the late shaft can be made to work, and it's the only option for most anyway since the early shaft is no longer available new.


...that is only if you have an existing 'late shaft' type trans and can just go with the 3.8 parts in place of the 4.06...late style only...



The overall moral is ...easy trans to change FDR on are the late type '3 piece shaft' design....the rest will give issues ....

What are our options for changing just the 5th gear ratio? I would like to lower the rpm about 500 - 800 on the highway.

Why would you want to keep shorter gears 1-4? I have a N/A 3L and dont use 1st or 3rd for daily driving.

Good point. I would like a lower ring and pinion also, something around 3.20 - 3.50 would work. I wish it was as easy as the dragster, I can change to a different gear in less than a half hour.