Going to 4.56's

Chris97K1500 · July 3, 2004

Well after toasting my tranny last week while towing, I've decided to take some strain off the tranny by upgrading from 4.10's to 4.56's. I've read a few post, but I'm not sure what manufacturer to look at. Precision Gears, Genuine, etc. What kind and where have you all gotten yours from? Do I have the 8.2" IFS or 8.25", I know I have the 10-bolt rear. Also, do I NEED a ring and pinion installation kit? How much do they typically run? A friend of mine will put them in for $150 an axle if I buy all the parts. Thanks, Chris

Shotgun · July 3, 2004

Well Chris I can't answer all your questions but I can tell you after much research I decided to go with Yukon gears. Yukon also sells the bearing and seal kits which are a step above OEM parts. I paid $1200 for mine installed.

frdfandc · July 4, 2004

Just remember that you will have to swap the front diff gears also. If ya do, BOOM, something in the drivetrain will break, usually the transfer case.

Yes you will need a install kit. Make sure you get a FULL install kit. If you look at Richmond gears in either Jegs or Summit, they have 3 styles of kits.

A basic kit - pinion shims, crush sleeve, pinion seal, and cover gasket

Complete kit - same as above plus pinion and carrier bearings, ring gear bolts, marking compound and some other small items.

Mega kit - same as complete plus - axle bearings and seals

You also probably want to purchase a complete shim kit for the carrier.

Your diff is more than likly the 8.25". The 8.2 was early model 10 bolt rear from the mid 70's and earlier. But I would call first before buying anything.

Chris97K1500 · July 4, 2004

Thanks, appreciate the help. I'm going to check out a few places before I let my friend work on it. Thanks again, Chris

Timd1971 · July 4, 2004

don't forget to get a Hypertech Power Programmer for your year also... EBAY! I got mine for like $200...sure beat the hell out of $400!

need it..so u can tell the computer what gears and tire size u have so everything works right!

snoman · July 4, 2004

Well after toasting my tranny last week while towing, I've decided to take some strain off the tranny by upgrading from 4.10's to 4.56's. I've read a few post, but I'm not sure what manufacturer to look at. Precision Gears, Genuine, etc. What kind and where have you all gotten yours from? Do I have the 8.2" IFS or 8.25", I know I have the 10-bolt rear. Also, do I NEED a ring and pinion installation kit? How much do they typically run? A friend of mine will put them in for $150 an axle if I buy all the parts. Thanks, Chris

I would say Precision or Yukon. I have a catalogs for both. Make sure you add a aux tranny cooler too if you have not already done so. .

intruder217 · July 4, 2004

Should you consider investing the money into beefing up your transmission? Seems to me that a quality rebuild with stronger components, an appropriate convertor and a hi capacity cooler would be less money andaggravation than changing the gears on both ends. And your hiway cruise RPMS and mileage will stay the same.

snoman · July 4, 2004

Should you consider investing the money into beefing up your transmission? Seems to me that a quality rebuild with stronger components, an appropriate convertor and a hi capacity cooler would be less money andaggravation than changing the gears on both ends. And your hiway cruise RPMS and mileage will stay the same.

No really, far to much is placed on tranny being at fault and not gears and tires. It is very foolish to belive that with big tires and a small block in a heavy truck that a 1900RPM cruise is good and yield better mileage and life. As you increase the load on truck it needs to be geared deeper to properly handle it. If he installs 4.56 and a cooler it will hold up fine no to mention that it will reduce strain and tranny, engine and Xfer case too. A few extra RPMs does not hurt a engine nore shorten it s life and in some cases it can improve it through reduced cylinder and bearing loading at any give vehical load plus most small blocks make best power above 2500RPM or so and deeper gear put it closer to its sweet spot when towing or even in OD cruising and when a engine is in of near its sweet spot it uses the less amount of fuel per HP/hr delevoped. If it takes say 50HP to drive truck at 65mph, it take 50HP regardless of engine RPM (HP= torque x RPM) so at a lower RPM the engine must produce more torque to drive it.

frdfandc · July 4, 2004

Technically you should upgrade both the transmission and the differential gears. Beefing up the transmission will help with how much abuse the transmission can take. Upgrading to a different gear ratio will help reduce drivetrain wear and tear during towing, because they will help get the vehicle going with less work.

Example:

If vehicle has lets say 200 ft/lbs of torque (this is what gets the vehicle going) and you have a 1.5 gear ratio in the rear end, this would be equal to the engine acutally making 300 ft lbs of torque.

Now take the same exact vehicle with 200 ft/lbs of torque and then make the vehicle have a 2.5 gear ratio, this would be equal to the engine making 500 fl/lbs of torque.

By increasing the rear diff gear ratio, you are increasing the effectiveness of the avail power the engine is producing.

snoman · July 4, 2004

No need to upgrade tranny, just fix it change gears and add a cooler and you will be fine. I have not lost a tranny in over 30 years and I have really worked a few of them too but they all had aux coolers and proper gearing for load. I have a 89 4x4 burb with a 700R4 that has been across country more than a dozen times fully loaded and then some and seen heats of well over 100 and been up pikes peak 3 times (two times fully loaded) and over every mountain pass in CO, WY and MT that are challanging more than once in summer heat and my tranny is 100% STOCK still with 170k on it now and it works as good as the day I bought it new but it has always had a aux cooler on it too. It was in Colorado for several weeks last summer in the high country and it is going back again next year too. It was also 100 when we were at Mesa Verda in CO last year while climbing up and down it roads there fully loaded too.

Chris97K1500 · July 5, 2004

The rebuilt tranny is going to be "much" improved according to his exact words. It will be beefed up. The truck already has a tranny cooler installed by previous owner. I'm going to go by my local 4x4 performance shop tomorrow and see what they can do for me. I really do appreciate the help. My new Off-road Adventures magazine had a situation almost exactly like mine, except with an '88 Burb. They recommended 4.56's with 35's as well. As far as needing my PCM upgraded for the new gears, Wester's will redo mine for shipping costs ($45, I think). Thanks again, Chris

snoman · July 5, 2004

You might even consider 4.88's if the load you tow is sizeable with those tires.

Chris97K1500 · July 5, 2004

I'll be getting a DuraMax/Ally is a couple years, plus I only tow an 18ft trailer with 3-4 ATV's, father in law has the diesel we tow farm equip. with. Trailer I tow only weighs around 3500-4500lbs max. I think 4.88's may be a little much. I may actually go back down to a 33-34" tire next. Chris

snoman · July 5, 2004

If you are planning on going down to 33's or 34's stay with 4.56's then. The trick is to try to keep converter off on stall in in stator "lock up" (not TC clutch lock up) which happens around 2500 rpm with a stock converter when pulling hard for a period of time to minimize heat build up in tranny.