Anyone change fro. 3.73 to a higher gear ratio?

[AllanB]

I know this is a drivetrain question. But i posted it in the 6.4 section, because I only want to know if anyone has done this on a 6.4
Any of y'all ever go to a higher gear than the stock 3.73, like maybe a 3.55? If so, what were the results? Did it knock down your track times? Did you get a MPG increase or decrease? If you did increase millage, was it on the highway or in town?
I don't do any towing to speak of, and I am was thinking about changing the gears out invthe rear and see if I would get a little better millage. But I don't want to suffer when I take it to the track

 

[Crack85]

pretty sure bigrpowr did this, maybe he will chime in.

 

[AllanB]

Thought I would bump this back up. Anyone out there had any experience with this?

 

[6.4psd916]

Some came stock with 3.55's. I remember one guy put 3.31's in his I believe. Was also another thread about it recently. What are your rpms at 70?

 

[Smokyred]

I've thought about it too, but I don't think you would see enough mileage gains just going to 3.55's to make it worth regearing both axles. If I did it I would go to 3.31's.

Dave

 

[AllanB]

Some came stock with 3.55's. I remember one guy put 3.31's in his I believe. Was also another thread about it recently. What are your rpms at 70?

I believe they are around 2000/2100 at 70mph.

I've thought about it too, but I don't think you would see enough mileage gains just going to 3.55's to make it worth regearing both axles. If I did it I would go to 3.31's.

Dave

A milage increase would be nice, but I can live with what I am getting now. I generally don't drive 70mph. On the interstate I may be running anywhere from 70mph to 85mph. Which is one reason I was wonering about this. It would be a lot easier on the motor when I am driving several hours. Also I have a 2wd.
I wonder how it does with the shifting and tuning. If a person would lose some time, or possibly pick up some? How it drives in town?

 

[6.4psd916]

That's right where I am, I got the same milage highway when I had my 37's because rpms were a shade above 1700. I would love to put some 3.31's in mine, probably get my rpms back in that same range.

 

[AllanB]

1700rpm's at 70mph would be great. As long as the truck still ran well. I am still wondering how well it would perform in a 1/4mile. I do know that if I am out on the interstate and start messing around with a Mustang or Challenger I will start running out of gear pretty quick. Which makes me wonder, these guys that are running 10's must be getting pretty high on rpm's.

 

[forcefed6.4ford]

Corb did. I think he went with 4.10's.

 

[AllanB]

Corb did. I think he went with 4.10's.

410's are the wrong direction lol. I want to go higher, not lower.

 

[forcefed6.4ford]

Misread.

 

[6.4psd916]

If I did my math right, going from 3.73 to 3.31 would put me a little over 1800rpms from 2050rpms at 70, 3.55's about 1950rpms, that's with 305/50r20 tires. Yours tires look close to that also. Just throwing that out there.

 

[AllanB]

If I did my math right, going from 3.73 to 3.31 would put me a little over 1800rpms from 2050rpms at 70, 3.55's about 1950rpms, that's with 305/50r20 tires. Yours tires look close to that also. Just throwing that out there.

Thanks for the info. My rear tires are 305/50. You hit the nail on the head. Got a few things to do to the rearend suspension and then I will try 331's. I will let ya know how close your numbers are. Thanks again.

 

[Kind]

Mine came with 3.55's.

You shouldn't see a loss in track times given you shifts will be less often... Something we can get away with being as we have enough tq to pull. As well as loading the motor more.

I will be switching to 3.31.

 

[Motostroker]

I thinks Aaron's drag truck has 3.31s, mainly to put a bigger load on the motor to light the turbos.


Sent from the drivers seat of a Fire breathing 6.4

 

[Dzchey21]

My crew cab came with 3.73 it has 3.55 now and I wouldn't trade them for anything. Mileage is better and tows 11-13000 lbs great

My reg cab has 3.73 prob needs 3.31 but i'm going to try something else to help load the turbos.

Imho for a 6.4 with 35s or smaller needs 3.55 no matter what.

 

[SouthFlstrokin']

3.31s would woork great imo

 

[AllanB]

Thanks, I am running a passenger tire about 32" I think the 3.31's will work good. We will see. Thanks for the info.

 

[SouthFlstrokin']

i ran the same tire, i kinda liked the 373s with my less powerful 7.3

but since your truck has a little bit of a bigger sack, i think some 3.31s would make it a killer hwy truck

 

[6.4psd916]

I just have to change out 2 sets of gears. Wouldn't, mind only having 1.