Adding overdrive gear and lower rear gear

[MT Jeff]

I have an 02 Dodge Ram with a 4.7 4 speed auto and 3.92 rear. The 1st gear is 3:1and overdrive is .75 with 32 in. tires. I can change transmission controllers and add a .67 5th gear overdrive with a controller swap. According to my calculations if I change the rear to a 4.56:1 I would only change my cruise at 80 by 70rpm. But my first gear overall ratio would change from a 11.7:1 to 13.7:1. With about 300lbft of torque at 3500rpm I get 300x11.7=3510lbft torque vs 300x13.7=4110lbft torque. Or 600 lbft more in first at 3500rpm.

IF my math is correct and I think it is this sounds like a no nonsense upgrade to me.

Used transmission controller $50-100
Gear set and bearings $400

I know it won't add any real torque to the engine itself but for $500 for an extra gear and 600lbft in1st it looks like a no brainer to me.

Could someone check my math on this?

500 bucks for 600 lbft in 1st and basically the same cruise rpm and a 5th gear sounds like a good deal.

[runawy9]

Your math looks pretty close. I come up with 7 rpm increase. not 70 rpm at 80 mph like you did. Everything else looks correct.
You didn't figure in the price of the rear end swap in your budget?

[MT Jeff]

I can do the swap myself. I worked at Chrysler/Dodge dealers for 20+ years and have all the tools to set the rear end up.

[user-612937456]

Do you care to describe the overdrive ratio swap and a little more detail I would like to educate myself I own and operate a transmission shop but I've never been presented with this option

[Carnut1]

I would look long and hard at what upgrades you can make to the 4.7 for the same $. If it is a non H.O. 4.7 and you just bring it to 4.7H.O. specs the engine has a totally different personality and gets better mileage. Thanks, Charlie

[MT Jeff]

Do you care to describe the overdrive ratio swap and a little more detail I would like to educate myself I own and operate a transmission shop but I've never been presented with this option

The early 4.7 with 45rfe Trans have a separate TCM. Chrysler had a tsb for Jeep Grand Cherokee for a drone at highway speed and the fix was flash to the TCM that added a 5th gear. This only works on a couple years trucks Ram and Dakota with separate TCM. TSB doesn't apply to trucks. So you need a Jeep controller.

Latter they made them all 5sp and called them 545rfe and combined pcm and TCM into one unit. Most Ram truck owners I've seem to go back to stock without a Gear change.

[MT Jeff]

I would look long and hard at what upgrades you can make to the 4.7 for the same $. If it is a non H.O. 4.7 and you just bring it to 4.7H.O. specs the engine has a totally different personality and gets better mileage. Thanks, Charlie

I looked into that and may do that in the future. The differences I found where.
1 higher compression requires premium fuel
2 different heads but flow the same
3 different cams couldn't find any used at the time for a reasonable price
4 forged crank I believe not required
5 better intake this is next on list to do

I just put heads on this engine for a dropped seat so I'm going to run it for a while. I may look for a core engine for the future.
The HO intake is better and an easy swap. The 08 up intake is better yet but requires an adapter to convert back to throttle cable since it has electronic throttle and different throttle body bolt pattern and no provisions for cable mounting.

Thanks for your input, Jeff

[Carnut1]

I would look long and hard at what upgrades you can make to the 4.7 for the same $. If it is a non H.O. 4.7 and you just bring it to 4.7H.O. specs the engine has a totally different personality and gets better mileage. Thanks, Charlie

I looked into that and may do that in the future. The differences I found where.
1 higher compression requires premium fuel
2 different heads but flow the same
3 different cams couldn't find any used at the time for a reasonable price
4 forged crank I believe not required
5 better intake this is next on list to do

I just put heads on this engine for a dropped seat so I'm going to run it for a while. I may look for a core engine for the future.
The HO intake is better and an easy swap. The 08 up intake is better yet but requires an adapter to convert back to throttle cable since it has electronic throttle and different throttle body bolt pattern and no provisions for cable mounting.

Thanks for your input, Jeff

That may be all true but I never ran premium in mine and I find it hard to believe the larger valves make no difference and the cam makes no difference. I have driven both engines and noticed a huge difference in how they perform. I understand the "just put new heads on " part of the equation. Thanks, Charlie

[MT Jeff]

I know it makes a difference but this is about the difference with the added gear ratios. I plan to look for a complete engine to go through for a engine upgrade. It would take 50lbft at peak torque to equal this I think and work just as well with the engine upgrade later.
Was yours an upgrade you did or a factory install?

I just didn't realize how much different the numbers were with gearing changes.

[Carnut1]

Mine was in Wiffy's 2004 Jeep Overland 4.7 H.O. min. upgrades, ported throttle body, ported airbox and air tubes, K&N that fits stock airbox and one ported exhaust manifold, (don't ask). Wiffy could get rubber on all four to pick up a kid from school, took a hell of a beatin and never complained. Sold it with about 156,000 miles or think of it as 4 times that many quarter miles with her driving it!

[AMXstocker1]

How do you add a gear with software? that doesn't make since to me you can't physically program a in a new gear ratio.

[wyrmrider]

It's just the way the clutches are applied with these new trans
the7-8-9 speed trans are the same way
some have several almost identical ratios
some use one ratio thread on the way up and another on the way down or for kickdown
so yes- it is in the controller
plenty of info in the Dodge and Jeep sites for that trans

[user-612937456]

How can the controller change a .75 overdrive ratio .67 I would think that would take a tooth count change on a Sun and pinion gears although I can see manipulating the other gears like first year, first gear over driven, 2nd gear under driven, 2nd gear Overdrive, 3rd gear under driven, 3rd gear Overdrive. To give you multiple gear change options but I don't see how you can overdrive your Overdrive when you only have one overdrive ratio to begin with

[MT Jeff]

How can the controller change a .75 overdrive ratio .67 I would think that would take a tooth count change on a Sun and pinion gears although I can see manipulating the other gears like first year, first gear over driven, 2nd gear under driven, 2nd gear Overdrive, 3rd gear under driven, 3rd gear Overdrive. To give you multiple gear change options but I don't see how you can overdrive your Overdrive when you only have one overdrive ratio to begin with

They have three planeteries but where only programmed as a 4sp od with two second gears that were used at different times originally. With a programming change they added the .67 ratio. The same design grew to be the 68rfe six speed. They 5sp actually has six gears with two second gears. One is used for normal shift pattern and the other as a kick down gear so as to not drop as many rpm.

[MT Jeff]

Wikipedia has an over view under chrysler rfe transmissions. They have been used as 4,5 and 6 speeds in different forms and vehicles