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Terry Haines

Final Drive Ratio Changes

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...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???

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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

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Terry

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

 

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.

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...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?

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..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?

Edited by gamiller

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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.

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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?!?

Edited by gamiller

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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 ....

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

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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.

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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.

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Terry, can you tell anything from either of these pics? As in which output shaft my trans has (late or early)?

 

Trans1.jpg

 

Trans2.jpg

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That would be the previous owner's doings... He had it routinely flushed at a dealership so I assumed it had Ford Honey in it... I have the service records of it being flushed at the dealership last at IIRC 90k. Since I knew I was pulling the trans soon after I bought it and the fluid only had like 20k on it that i'd just wait.

 

It now has Royal Purple Synchromax... B)

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terry, for future reference, what is the earliest zetec trans i would need if i wanted to swap the taller gear ratio in my 98 trans? (i have the early shaft)

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95>97 Zetec rod shift..BUT you still need to check output shafts ,as I have said before,Ford did mix and match.For example I have seen some rod shifts with 200> output shafts and some Zetec Focus MTX's with 95>97 output shafts.The assy number on the trans means little.Only the trained eye can look at an output shaft and tell you if it is early or late..

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Well, unfortunately, I don't have the trans apart still. Guess i'll have to look next time the trans is out. With pics into where the shift tower would sit you could tell though right? So if I pulled the shift tower and shot some pics you could tell?

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I don't see the problem,the cases are open,remove the forks and fork shafts,reverse idler components and lift out the shafts!!

Why did you open the trans cases then??? :unsure: :unsure:

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Thanks Terry,

Pics are truly worth a thousand words.

 

So a fella can take any early 4banger for the parts (if in good sahpe) and just keep looking until he finds the correct 98+ V6 tranny to rebuild.

 

Then if he is smart he'd send it to you to put together and install a quaif or torsen and then bolt it up to his new 3L...... right! B)

Edited by Aussie Ford

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...that would be the owners choice. I have to say that I still see many who DIY an MTX75 and get in way over their heads. Need to understand the basics of the trans first and READ,READ, READ the full section on the Ford CD and be sure you know what you are taking on. This is not like the 'ol 'toploader' trans you had 30 years ago!!!

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...and just keep looking until he finds the correct 98+ V6 tranny to rebuild. ..

Not 100%. If he gets a late model Cougar V6,but without the revised VSS he may already have the later output shaft.Once again, a trans shop or someone with experience will know just by looking at the output shaft what type he has.The later V6 MTX's(Cougar) will only need the 3.8 later level output shaft and ring gear to change from the 4.06...as I have said many times, the year,assy number etc etc is no sure guide to the internals of any MTX75,Ford did mix and match components.The pics tell the whole story if you study them.

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What about a pic of that Late "about" 2k and on three piece shaft that is the easy one to do?

You gave us a pic of the early two piece and the one piece right?

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