simple formula I read somewhere to give you a ball park is


RPM X New Gear Ratio (4.56 or 4.88)
Old Gear Ration

so ex (1700rmp x 4.56)/3.55 = approx. 2100 rpms

Hope this helps

 

So approx. 2340rpms with 4.88's? Is that good, bad, ok? and this is driving 60-65ish

 

It is not that bad, but your city mpg will defiantly increase. That would put you a little higher rpms at highway speeds but your truck will be a whole new truck! It will get up and go better, it won't kick out of O.D. as easily if at all. But most importantly your truck wont have to work as hard to get those massive tires moving again. You city mpg's will deffinately improve and I would not be surprised if your highway miles even with the higher rpms improved as well.

Efuehrin is running 4.88 with the 5.4L and he is cruising at 2500 rpms, 75mph and said he gets about 12.5mpg. Which on a lifted truck and big tires that is not bad at all.

 

Well my speedo hardley ever hits 55-60 normally its right on 50 which is actually closer to 60. So my RPMS should stay below 2500 for the most part

 

Then you will definately want to go with them. They will save you a ton your truck will thank you for it. The driveablility becomes so much better with the gears in.

Plus even though our trucks are not racecars it will pull hard off the line. I have a friend with a similar set up who was pulling a boat and this stupid rice grinder pulled up to him at a light and was planning on blowing the doors off us so he could merge before the road ran out. It was priceless watching him have to hit his brakes to get behind us and the look on his face when a truck pulled that hard.

 

haha good info! 4.88's here i come! September is due day!

 

Have been giving this info out a lot lately so I figured we would add it to the sticky and send them to one place.


Some recommend gears are either ford racing gears, yukon gears, or precision gears. There are many good gears out there just take the time and do a little research.

To find your rpms with the new gears:

(new gear ratio) X ( old rpms)/ (old gear ratio) = new rpms
E.X.
4.56 x 2000 = 2445 aprox. rpms
3.73

And to find out what axle you have on the rear you can check one of two places.

1. Axel tag this is a little metal tag attached to the rear differential.
It will read something like this 975 73 LS.
The 975 in this tag means you have a 9.75" rear end.
The 73 means that you have 3.73 gears.
The LS is the designation for the Limited slip option.

2. Is the door code.
This can be found under the axle designation on the factory door sticker. If you have the H9 designation you will have the 3.53's with limited slip. If you have B6 you have the 3.73's with limited slip. I can not recall the other designations right now.

Along with gears you will need a crush collar, shims, bearings, pinion nut, seals, and oil. And if you do have the limited slip make sure to buy the bottle of Friction Modifier. Also depending on which gear oil you go with you may not need to add the friction modifier as it already comes in some (this is as stated on there bottles, however I feel more comfortable adding it just in case, better safe then sorry). I know Royal Purple and Lucas Oil already have it in them. The gear oil for the front is 75w90 and the rear is 75w140.


This is the link to where I got my gears:
http://www.accuautoparts.com/
Again there are many other places to order this is just one.

 

Another important point is the break in period.

Quoted from ring-pinion.com

New Gear Break-In
"Do we really need to break-in a new gear set? I have heard many people say "When I bought my new truck no one ever told me to break-in the ring & pinion." Whenever we are blessed enough to afford a new vehicle, we take it easy on the engine for the first few hundred miles. While we are pampering the engine (probably for the last time ever), the ring & pinion set goes along for the ride and gets a chance to break in before we hammer the throttle.

In most stock vehicles with stock tires there is seldom a risk of a burned gear set. For those of us who modify and use our trucks, there many situations that can contribute to burned gear syndrome. Motorhomes, towing, tall tires, and high numeric gear ratios (4.56 & up) can all generate a lot of heat and cause the gear oil to break down. The greatest damage to a new gear set results when it has been run for ten minutes or more during the first 500 miles and the oil is very hot. Any heavy use or overloading while the oil is extremely hot will cause it to break down and allow irreversible damage to the ring & pinion.

In order to make them run cooler and quieter, new gears are lapped at the factory. However, they are not lapped under the same pressures that driving creates. The loads generated while driving, force any microscopic high spots on the gear teeth back into the surface of the metal. This is called "work hardening". Work hardening is similar to forging in the way that it compresses the metal molecules into a very compact and hard formation. This can only be accomplished if the metal surfaces are lubricated and the gear temperature stays cool enough that the molecular structure does not change. If the temperature of the metal gets hot enough to change the molecular structure, it will soften the surface instead of hardening it. This may seen like a balancing act but it all happens easily & passively as long as the oil keeps the gear cool while it is breaking in. Some of the synthetic oils on the market today can help a gear set live longer. I've had great success with Red Line ®, Torco ®, and Richmond Gear ® synthetic gear oils. These oils will continue to lubricate at temperatures where many crude oils break down.

Even with synthetic oils, I still recommend the following procedure for breaking in a new gear set: After driving the first 15 to 20 miles it is best to stop and let the differential cool before proceeding. Keep the vehicle at speeds below 60 mph for the first 100 miles. I also recommend putting at least 500 miles on the new gear set before heavy use or towing. During the first 45 miles of towing it helps to go about 15 miles at a time before stopping to let the differential cool for 15 minutes before continuing. This is necessary because not all of the gear tooth is making contact until it is heavily loaded. When towing, the teeth flex to contact completely, and cause the previously unloaded portion of the teeth to touch and work harden. All of this may seem like paranoia, but it is very easy to damage the ring & pinion by overloading before the teeth are broken in. If you take it easy on a new ring & pinion and keep it full of high quality oil, it should last a lot longer.

With regards to limited slip additives, I have found that using too much additive can lead to premature gear wear. Use just enough to keep the limited slip from chattering but not more than 4 oz for every 2 qts of oil. It is a good idea to change the gear oil after the first 500 miles in order to remove any metal particles or phosphorus coating that has come from the new gear set. This is cheap insurance and a good time to discover any problems before they grow to disastrous proportions."

 

I am considering a gear swap. Just replace my trans at 62,000 wasnt expecting that. I want more out of my truck and was considering 4.10s. I dont plan on lifting the truck. (I have stock 17s now). I do tow a boat around and travel about 300 miles round trip (highway) to our cabin on lake Oneida Ny. I have read the success of people who have swapped out with 4.56 and loved them however I feel that they might be too much for my truck considering I am keeping it stock. Any advice would be much appreciated.

Duane.

 

What ratio do you have now? If you have a 2 wheel drive truck the 4:30 ratio is an option.

4:10's would be good if you have something besides 3:73's in now. Which if you have a 4.6L you probabaly have 3:55s or higher. I"m not sure though.

 

Yep let us know more about your truck and we can help

 

Sry about the lack of info. Its a 4.6 4x4 that currently has that 3.55 gear ratio. Its an x cab if that matters and has the 4r70w trans.

 

Well, then I would probably do the 4.10's if you are absolutely positive your going to keep it stock. It is not a cheap mod, so you wouldn't want to just go 4.10's only to three years down the road decide you want to go bigger and then regret you didn't do 4.56's. You will notice a difference with 4.10's since you are running a 3.55 gear. And it will be roughly about $1500 for them to be installed. Hope this is what your looking for....

 

Thanks for the advice! I just ordered the gear set that comes complete with everything I need to do a 4.10 swap. It ran me just under 400 for all the parts and my cousin is goin to do the work on it. So the labor will cost me all of about a case of corona and mabey a lime or two. THanks for all the great info cant wait to get them in there and burn the tires off haha.

Thanks Again,
Duane

 

What brand of gears did you buy?