Just a little heads up but you 1200' higher then me in elevation. w/o F/I that is going to effect your mileage as well. I had cut the bowl in my intake top pan and did the exhaust and turned up the pump. 6500lbs is what the truck weighted. I was getting 9-12 loaded. so with the crewcab unloaded I think you would be to maybe do 18 or 19mpg with an overdrive. I really think that gears are something you really don't want to mess with unless you are going with a larger or smaller tires. 3 miles a gallon gain and not be able pull the load makes a truck useless. Gears may sound cheaper but its not something you can just change on the fly. leave the gears alone. Overdrive allows you to be able to go down the road at 65 closer to 2000 rpms. lets do the math mmmkay

30" tall tires(30*3.14) = 94.2 /12" = 7.85' for one full turn of the tire
5280' (mile feet)/7.85' = 673 tire rotations in a mile
65 mph*673=43745 tire rotations an hour * 4.10(gears) =
179354.5 crank rotations(1-1 ratio) /60 min = 2989 rpms

so 43745 * 3.31= 144795.95 crank rotations (1-1 ratio) /60= 2413.2rpms

so with an over drive .77 in the zf w/ 4.10's and 30" tires
179354.5(1-1) crank rotations * .77= 138102.96 /60 mins = 2301 rpms

E4OD has a .71 final drive ratio so w/4.10's and 30" tires
179354.5(1-1) crank rotations * .71= 127341.69 /60 mins =2122 rpms

Gear Vendor Under/Over drive unit final drive ratio is .78 so everything else the same
179354.5(1-1) crank rotations * .78= 139896.51/ 60 mins =2331 rpms
but wait there is more this thing doubles your gears so you are in a better operating rpm between all the gears.

I do not know the forumlas for the power loss ( i.e. what you can tow) but I am sure you will notice it with a gear change. hope this gives you a better idea of what your dealing with.

 

Thanks alot for all those RPM numbers, i really appreciate it. I was trying to debate changing the gears because i really dont do alot of heavy hauling and ive done 3 gear changes on my own in the past, so its relatively the easiest for me to do. I would like the E4OD swap the best i guess, however i will have to buy an expensive controller, thats the main reason, and have to modify drivelines , etc. Too bad i cant drive a conversion like this first and see what to expect, but i guess i can always reinstall the 4.10's if need be.. I will keep looking for an E4OD setup anyways thats reasonable, thats the best option for me with 4.10's

 

just to let you know
Electronic Performance Products -- Baumann Electronic Controls, LLC
for entire stand alone & harness for $550. Have to tune with windows.
I don't know if that is what you are looking for but doesn't sound to bad
If you were considering a transmission change.

 

I'm running that TCS setup and it's awesome but still not as cheap or fast as a gear swap. A good used E4OD will often set you back at least that much again unless you luck out. The other problem is swapping in a more expensive and more complex transmission of unknown history. I rebuilt mine before using it but that drives cost up even more. With a sterling full floater rear end, I can swap them in about 4 hours - its not a big deal and you can always swap back anytime you want (I still have my 4.10s stored somewhere). Just be sure to get a solid shim kit instead of that silly crush sleeve setup for the pinion preload.

 

Also factor in how many miles you average driving the rig a year and how many years you will be keeping it. It takes a lot of miles to ever pay for the swaps, if saving money is what you are after.

 

yeah thats why im just throwin a set of $200 3.31 gears and done with it. Just waiting for them to come . If im towing, i'll just drop in second or first on a hill. Towing is on how fast you wanna go over the hill, hehe, not much on ratio really.

 

Something else to consider for others thinking of this swap (I was once). You would be trading the C6 one of the toughest transmissions for an E4OD with bad reputation in heavy duty use. please don't take my word for it. When I was looking for a truck, everyone I found with an E4OD needed trans work. Check forums on making a E4OD realiable it is not cheap. A gear venders overdrive would be cheaper than a proper E4OD. Of course the gear swap cheaper yet if you can do it yourself, but you don't get the extra gear.

 

That's what I was thinking.

Isn't the T-19 a stronger tranny than the ZF5 as well?

 

I believe you are right but I don't have enough history with the manuals to say for sure. Myself I prefer a stick but my wife drives my truck also.

 

my truck is a 94 crew cab dually w/7.3(nonturbo) ZF5 and 4.10 Limited Slip.

I cruise at 58mph (2k rpm) and consistantly get 20 on shorter highway drives, and 21-21.5 on longer ones (2 hours and longer)

im runing General Grabber AT2 tires on all 6 they are 235/85 r16

 

btw, the single mass flywheel conversion is a MUST!!!!

my truck has 235k miles on it, and i took it in for clutch work about 2k miles ago (clutch was ALWAYS at least 50% engaged) and found that my original clutch still had a bit of life in it, but the flywheel was falling apart, very literaly, hence the lack of disengagement.

 

Yes, The T-19 is allot stronger.

 

How strong is the ZF ? I have a one i was gonna use , however im just gonna swap gears next week.

 

I think that its a pretty good transmission, I haven't had any problems with it.

and, I do put the whole truck through is paces when appropriate. My only complaint is that i wish i had a couple more gears

 

the ZF is strong enough to snap transfer case chains, snap axles, strip the teeth off of ring gears, and twist driveshafts up into pretzels.
i found the weak point on the ZF is the shifter where the handle bolts to the shift head, and the pos dual mass flywheel. .