hmm is right. if you have to be told how the diff works, do yourself a favor and keep away from it

 

my truck 4.10 4sp 100=2400 rpms
your truck 4.10 c6 100=2600 rpms
da85 truck 4.10 c6 100=3000 rpms
somthing wrong with this picture c6 can't lose 600 rpms.
anybody have a chart that has 3.08 1 to 1 32" tires=rpms help
I think you will not want overdrive 3.08 may be optimum or less rpms

 

I do my speed calculations with a spreadsheet.
So I just enter gear ratio, tire diameter, transmission ratio and RPM to calculate speed.
I have also looked at several tire manufacturers sites to get average diameter loss for tire sag at the bottom of the tire due to the weight of the truck.
Most 32" tires propperly inflated work out to an average diameter of 31.5 inches sitting on the ground.


OK did I do this right, if I divide MPH by .611 I have KPH?

61.1 MPH is 100 KPH?

With a 4.10 gear on 32" rubber at 100 KPH the RPM would be 2655 with a four speed in direct drive figuring it mathematically.

Changing nothing but the gears to 3.08, 32" tires, 2655 RPM, four speed in direct drive, the speed would be 133 KPH.

Figuring it another way, 32" rubber, 3.08 gear, 4 speed in direct drive, 100 KPH would be 1995 RPM.

One more way, 32" rubber, 3.08 gear, 4 speed in direct drive, 3300 RPM would put you at 165 KPH.

Since the C 6 does not lock the torque converter, wind, inclines or even the condition of the torque converter and tranny fluid could change the RPM at a given speed.

Have any of the speedometers above been checked with radar or using a measured distance and a stop watch?

We have measured miles several places around here, 60 MPH you travel one mile in 60 seconds.
A measured kilometer at 100 KPH should take 36.66 seconds if my math is right on the conversion to metric.

 

my speedometer checks deadon with all the radar signs dont know about my tach though. your figures probably right my tach shows 2400 at 100 with 235 85 16s but could be off

 

Those calculations were for 235/85-16 mud tires, 31.72" tall.

 

Ya right lol, I wish. It would cost 1000 in fuel to get there lol.

 

No dude, mine does 3000rpm at 100k.

 

OK, I can take a hint lol! (sorry for the techno-babble)

From the top....
There are two seperate gears that we are conserned with in the differential for a swap, the ring gear (not to be called rack), and the pinion.

The pinion gear is mounted perpendicular to the axle and is what the driveshaft bolts to. This is the smaller of the two gears. It runs on a double cone roller bearing similar to the front wheel bearing of the truck (more on that later).

The ring gear (named for its shape) its driven by the pinion gear, and rotates on the axle, so it engages the pinion at a 90 degree angle.

Now the ring gear has a set of bolts that hold it in place on the CARRIER. The carrier, has the main guts of the differential in it. To get the ring gear out, you will have to pull the whole carrier out of the differential housing.

To get the carrier out, first pull the axle shafts. The truck will have to be in neutral (take all precausions to secure the truck) to take any tension off the drivetrain. When you pop the hub cap off, you will see two sets of bolts, one is the lug nuts that hold the wheel on the truck, the other, is smaller, and holds the axle shaft in place. If you take those smaller bolts out, the axle shaft can slide out of the truck, but may need to be tapped with a mallet to lossen the seal.

Once both axle shafts (one for each side) have been removed, the two bearings that hold the carrier in place can be removed. There will be two bearing caps, one one each side of the carrier. Unbolt them, and the carrier will fall out, so be carefull here, have a stand of the right height (a strong crate, or wide wooden block will do) and roll it out of the differential housing. My best guess is that the carrier weighs up to about 100lbs, heavy enough to be a hazard under the truck, but still light enough that you can get it up on a work bench.

Remember those ring gear bolts I mentioned? you will find them on the back side of the ring gear (opposite side of the teath). Pull those bolts, and the ring gear comes off. Your new gear will not be as thick, since the pinion is larger (larger pinion (more teath) and smaller ring gear (fewer teath) means faster truck ).

You will need a torque wrench to bolt the new gear on the carrier (I think princess auto has a store in edmonton, their prices are good). Get one that has a range up to 150 Foot Pounds. The bolts will need to have locktite on them so thay can't work loose, the ring & pinion set should have instructions on which type to use, as well as the correct bolt torque.

On to the Pinion.

The pinion bearing is supported on two roller bearings. The bearings are tapered like a cone such that they "point" to each other. The advantage of this type of bearing is that it can support load in both directions, along the shaft, and across it, essential for the bearings to survive.

The catch here is than the distance between the two cone bearings has to be exact, too close, and it jambs the bearings like a wedge, to far, and it has slop in it. In automotive wheel bearings, this distance is held with a nut that is locked with a cotter pin, so its adjustable and no actual torque is ever applied to the nut (there is some but its very little). But in this differential, 300 foot pounts of torque is applied to that nut, this is possible by placing a precicly sized spacer between the two bearings to keep them from crushing against the outer bearing race (the outer race is a piece of hardened steel that matches the angled shape of the cone bearings, it is pressed into the differential housing, do not disturb these).

The pinion nut torque and correct bearing spacing of the pinion bearings is called "Pinion PreLoad".

From factory, there is a crush sleve that is used as the pinion spacer, as torque is applied it crushes at a specific point, and produces the correct preload. An easier way to do this, is to get a differential shim kit, or just get shims as needed. A differential shop should have these, or you can order them at the same time as the gears.

The shim kit (aftermarket only) will replace the crush sleave with a solid spacer, and then the correct distance is set using small spacer shims (basically there just really precice washers made of high grade steel). Now you can use a big socket wrench and cheater pipe to squeese the water out of the nut without having to worry about a specific torque, just use the same anount of force as what was needed to remove the pinion nut in the first place.

Breaking the torque on the pinion nut is the first part of dissasemly

This way, you can use the weight of the truck to keep the pinion shaft from turning, since there is no bolt on the other end to put a wrench on.

You have to drop the driveshaft at the differential first, inside the yoke (the thingy that the rear of the driveshaft bolts to) you will see a big nut, if you can't break the torque in this thing, you can't do the swap. If you get the nut off, the yoke will slide off the pinion shaft (may have to gently pry), and this will expose the shaft seal. You can use a seal puller (special too) or a screw driver and small hammer to gradually pry it out. Don't worry about wrecking the seal, you will need a new one anyway, but be carefull not to damage the differntial housing itself.

I hope I didn't confuse anyone even more. If I missed something just rub my nose in it .

 

My tach is not accurate above that speed, the highest it will ever read is 2450, which is fine cause I hardly ever go that high anyway .

When I first got the truck I thought it had 3.55 gears because of the faulty tach, you may have the same situation.

Dave S, your conversion calculations are correct.

 

Cool, I can now calculate KPH with my spreadsheet.

So if you start off with 4.10 gears and a C 6 and shift at 2000 RPM, your 1-2 shift is at 30.62 KPH (18.7 MPH).
At 2000 RPM the 2-3 shift is at 51.6 KPH (31.52 MPH)
And in third at 2000 RPM you should be going 75.33 KPH (46 MPH).

 

what size tires are you running I know you lose some with c6 but cruising on flat ground I didn't think that much. dave shows 4sp at 2655 so you are losing 345 losing the same with 3.08s would put you at 2340 not too bad add gearvenders eventually looks like 1840 at 100 you might lose a little more with 3.08s but I think that would be perfect light loads or hills drop back to direct 2340 should be good for fuel

 

I havent ever bumped the governor on this truck but have had it over 3000 .
speed limit here is 75 mph set cruise 72 to 74 16 mpg takes big hill to lose anything on cruise. I dont pull much anymore and have a spare set of 3.55s thinking about trying them to see how I like them 1 or 2 mpg would be worth it.

 

You got it!

Man, seeing those numbers again brought it all back, my truck really sucked with 4.10s, 2000 RPM, and only at 46 mph....(suppressed memory).

Heres where I am now: 1-2 @ 35KPH 2-3 @ 62 KPH and (my personal favorite) 3-4 @ 96 KPH. Wider first and second gear ratio bring down the upshift speed slightly compaired to the C6.

2000 RPM with C6: 96 KPH (assumes zero slip)

2000 With E4OD : 135 KPH

As far as TC slip goes, it depends on how fast the engine is spinning, the faster it spins, the less the slip. My E4OD slips a minimum of 100 RPM when the engine is turning 2400. If I'm running at 70 mph, there is nearly 400 RPM difference between locked and unlocked TC (in 4th).

I mention this because a GV overdrive is most effective with lower gears. If you have 3.54s or even 3.08s, you will not get the full advantage of the mechanical gear ratio, because the TC slip will increace as you approach the theorietical stall RPM threshhold. After you get to the stall speed of the torque converter, no other changes are possible in actual drive ratio. The transmission will also produce more heat depending on the amount of load and how much of the final drive ratio is being affected by the TC (more slip = more heat).

I should also mention that the TC I got for mine was actually considered a "low stall" type, my point being, you can change the gears, or get a GV, but if you have a C6 tranny, its not worth doing both unless higher top speed is all you're after.

 

And you're right, thats what I'm after. High top speed, and good fuel milage

 

Holy crap man, what are YOU doing up this late lol??? aren't you an hour ahead of me?

The thing with open TCs is that one you are floating in the "shushy" zone near stall speed, your RPMs may seem relatively low, but the extra slip will cost you some MPGs as the heat gets generated. If you want to cruise @ 100 KPH, 3.08s will give you a good RPM, but if you activate a GV overdrive, the drop in RPM will be negligible. Besides, the E4OD has a bigger overdive ratio anway! I gotta hit the sack.