My fellow FORD truck enthusiasts,

I would like to take this opportunity to, in advance, thank all of you for your wisdom. I am looking to change my rear end gears from a 2.73 ratio to a 3.55. I would like some thoughts on this. My goal is to make my truck pull like a tractor,lol. I have a 96 f 150 with an I6, Eddie Bauer edition, 5 speed tranny. I am pretty sure I have an 8.8" rear end. I found a tag bolted to the rear differential that reads as followed: S842M 273885K25. anyone know the spline length? I also found a stencil on the housing near the drive shaft which reads: FOTW 4025 AA. Also, needed to ensure my tranny is in fact a M5od-r2. On my driver side door, under the word transmission I see the letter "M". Also on the driver side of the tranny I found a bar code which reads as followed: F0tw 4025 AA. Also I am looking to upgrade my clutch. I am not sure which one I have but I would like to get the best for my setup. Thanks guys... looking forward to the feedback.



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The easiest way to do this is find a rear end that has this gear ratio, very common and swap the whole rear end. This is an easy DIY job versus special tools to set up the differential after the gear swap.

 

I want everything new and I am going to take it to a shop that specializes in this sort of thing. Thank you for the reply.

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Transmission code M denotes it is the Mazda M5-R2. Your truck has a 8.8" rear end with 31 spline axles.

 

What size tires will you be running? You can get away with more gear then 3.55s, especially if your like me and drive the speed limit on the interstates.

I believe 4.10s would put your RPMs around 2300 at interstate speed with factory sized tires.

 

Thank you rla2005. I am wanting to purchase the new gears through summit and I really needed the spline length. I figured it would be 31" or 28" What is your o2 about the mazda tranny?


Garthneddy,
Thanks for the feedback. I only live 6 miles from my workplace and they are all back roads. I do not plan to travel on the interstates with it but I do in fact do the speed limit most of the time. Switching to 4.10 gears will put a lot of strain on the motor correct? But if I can get away with it then I ll go that route. My plan is this: switch gearing, upgrade clutch, add new front, rear, and oil pan seals(Making sure my motor is running in its top condition), and lastly put a turbo on it to further increase hp/torque. All im worried about it torque tho. I ll only be running 5 or so lbs of boost. nothing extreme. Also, my tire size is p235/75 r15


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Why do you need the spline length to order gears?

 

I was wondering the same thing

 

probably the number of splines 28 or 31 instead of length of them.

 

You guys are right. I meant the count not the length

 

I'm looking at getting the part number 14-0066 from summit racing. If this helps. Thanks for the replies

 

Well that's a kit with 4.10's. Didn't you want 3.55's?

 

Yes sir but Garthneddy suggested I may be able to get away with 4.10s. What kind of difference do you think it would make?

 

I'm going from 3.55 to 4.10's, but I'm running 33's. If your going for towing 4.10 will help some, but you might find the truck running out of breath quickly. The I6 does not like high rpm's.

 

Well what is your suggestion Evan?