4.09 gear with the new calibration kit on the 18-20 GT

[Briebee72]

I'm curious about this as well. I have the 10 spd auto and i have the new 2018+ calibration kit installed. Anyone know if it is advantageous for us to go with the 4.09 ratio or the 3.73?

So I talked with ford performance today about this. They said the 4.09 gear in the auto is fine. The transmission is strong and there are no known problems. That the first gear shift would be super quick though. And would come down to personal taste if acceptable. I have the 3.55 gears now and I have been told and read that going to the 3.73 really would not be worth the cost for such a small jump which is why Im curious about the 4.09. If this was a cheap easy swap out would be fine to try it but it's costly to do and then if you dont like its costly to go back which is why im trying to get all the info I can before i make a decision.

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[Pandajoshy]

So I talked with ford performance today about this. They said the 4.09 gear in the auto is fine. The transmission is strong and there are no known problems. That the first gear shift would be super quick though. And would come down to personal taste if acceptable. I have the 3.55 gears now and I have been told and read that going to the 3.73 really would not be worth the cost for such a small jump which is why Im curious about the 4.09. If this was a cheap easy swap out would be fine to try it but it's costly to do and then if you dont like its costly to go back which is why im trying to get all the info I can before i make a decision.

How much is it to get installed?

 

[Rock&Roll]

Intersting

I have 3.31 gears in a Stick and I have no desire to go to 3.73.
I drove a 3.73 and thought it was to quick of a shift ... YMMV

 

[Pandajoshy]

https://www.steedablog.com/2017/12/18/2018-mustang-drag-car-rear-gears/

Here's a Steeda blog where theyput 4.09 gears on the 10 speed auto. I wish it would have gone more in depth though.

 

[Hack]

So one of the main reasons I bought the calibration kit was to install the 4.09 gear. Ford really does not say one way or another if is best on manual or auto. I have an Auto. I was told prior to this kit not to put a 4.09 on an Auto they were mostly for manuals. Im new to gears and am a little lost when searching the net as no one really is clear on the matter. several sights now, since the kit came out, are sold out of 4.09 ford performance gear kits. So I assume lots of people are going to put this option in. anyone here doing it? Know the cost about to put the gear in? Are you putting it in a manual or auto? Just trying to feel this out as it is something I really want to do. Any other thoughts on the matter I should consider?

I knwo about the top end speed and fuel consumption allready but anything else? Other then I am sure rear tires will go bald even quicker.

Whether it's a good idea or not depends on what you want. The 4.09 benefit is the car will have more available torque at the rear wheels on launch. So, if you are a drag racer using a sticky tire or if you love spinning the tires really easily - I believe those are the main differences you will notice. And if you shift the automatic manually you will notice you have to shift more frequently.

I would think it will be a good change for an automatic car. Launching hard with sticky tires is always fun.

 

[Ebm]

Whether it's a good idea or not depends on what you want. The 4.09 benefit is the car will have more available torque at the rear wheels on launch. So, if you are a drag racer using a sticky tire or if you love spinning the tires really easily - I believe those are the main differences you will notice. And if you shift the automatic manually you will notice you have to shift more frequently.

I would think it will be a good change for an automatic car. Launching hard with sticky tires is always fun.

Can confirm, have MT-82 and 4.10s, the gearing makes up for the lack of low end torque. In a 10 speed car, I wouldn't go any higher than a 3.73 with thick meats on the back. On the newer MT-82s with horrible ratios, I wouldn't hesitate to go 4.10s.

 

[Briebee72]

Whether it's a good idea or not depends on what you want. The 4.09 benefit is the car will have more available torque at the rear wheels on launch. So, if you are a drag racer using a sticky tire or if you love spinning the tires really easily - I believe those are the main differences you will notice. And if you shift the automatic manually you will notice you have to shift more frequently.

I would think it will be a good change for an automatic car. Launching hard with sticky tires is always fun.

I was meaning if its good for the car or not in the physical sense. Like is there a reason an auto should not have it done as I dont see many with it. Is there a chance its gonna f the car up or damage the trans because its not meant for the auto... stuff like that. Thats the info I cant find a clear answer on.

 

[Briebee72]

How much is it to get installed?

IM not sure as I have not called a dealer yet to find out but , from what I have seen in othr threads loks like people who took just the pumpkin to thier frined mechanics paid about 400.00. The whole job, as in the whole rear end has to be disassembled Im thinking is about 1200 to 1500 from what I am seeing. PLus it has to be done right or there can end up being a gear whine which would mean the whole thing has to be taken apart again. and then if you dont liek the gear to have it put back to regular..... well you get the idea.

 

[Hack]

I was meaning if its good for the car or not in the physical sense. Like is there a reason an auto should not have it done as I dont see many with it. Is there a chance its gonna f the car up or damage the trans because its not meant for the auto... stuff like that. Thats the info I cant find a clear answer on.

A steeper rear gear gives the engine and transmission more leverage over the rear tires. So if you don't change anything but the rear gear, it will be easier on the transmission.

It will potentially be harder on the drive axles though - especially if you add stickier tires. And if you end up with a lot of wheel hop, that could be harder on other things up the line including the transmission. But that is the same with or without gears. If you regularly have lots of wheel hop it's a good idea to do something about it.

 

[spaz mk will]

OP, here’s a thread on this topic that would probably interest you. @Mikepol2 has done 4.09s but on the 6MT.

I agree with others that this is a bigger help for 18+ 6MT cars due to the long gearing. Something I may do farther in the future if I want more power while staying N/A.

https://www.mustang6g.com/forums/threads/how-are-people-liking-4-09-gears-in-the-mt82.111146/

 

[Briebee72]

OP, here’s a thread on this topic that would probably interest you. @Mikepol2 has done 4.09s but on the 6MT

https://www.mustang6g.com/forums/threads/how-are-people-liking-4-09-gears-in-the-mt82.111146/

Thank you, yeah thats my issue I can only find info on the manuals. IM specifically looking for how it works out with the autos. I will take a look at that thread though thank you.

 

[IrishStallion]

As stated great for 6 mt gen3 cars, but I’d be hesitant on a10 car. My 3.55 geared a10 has super quick first gear already. Unless your running drag pack all the time (most do not) I would think car would be slower on street tire due to excessive wheel spin.

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