Are you guys that are running these gynormous tires doing anything to correct the speedo?...if not...the mpg's you are calculating will be way off regardless because the miles traveled per tank will be off due to the inaccurate speedo...a vicious cycle.

Now a re-gear does NOT affect the speedo because of where the speedo pick up sensor is located...but you would need a tuner to reprogram the PCM for tire size change...

Just thinking as I type.

Joe

 

X2...couldn't agree more...very well said in a nice concise manner!

 

This is all fine and dandy for you V-10 gas guzzlers, but what about us 6L PSD drivers?!

With a measly 4500rpm redline we have far fewer revs to work with!

I've got the original 3.73 LSD in my 4x4 with 33.5" tires and am towing my car hauler. I don't plan to go any bigger on the tires but I'm thinking the 4.56 gears would be a better match and according to the FTE ratio calculator that will get me to an effective 4.28 ratio.

 

LWW...you are 100% correct about 4.30's and V10...

As far as optimal gearing for the 6.oH and 7.3...I don't know...but I do know that some of the PSD's (6.4L I believe?) came factory stock with 4.88's!!!...

 

i'm planning on going with 4:56s and a tru-trac in the rear when funds allow. after i may jump up to 285's. i dont really tow but i want neck snapping off the line power. so long as i can still hit 100 without running a crazy rpm i'll be happy.

 

y not go bigger lol!!

 

Yeah...how about us PSD 6.0 drivers? I think our problem is similar but much more subtle. I also think smaller changes in ratio than what you are considering are perhaps better. My experience is that the best fuel economy and torque combination is right around 2000 RPM. If you run 4.56 gears, you will be sitting at about 2280 RPM at 70 mph. This may be OK for you. I think right now, you are running at only about 1865 RPM.

If we go to larger diameter tires, the RPM drops away from the ideal (2000 RPM) when towing at 68-70 mph in 5th gear. This problem keeps me from considering the factory 20" SD tires/wheels (34.1" diameter). A simple change to 4.10 gears would swing this -7.7% error to a +2.1% error--increasing the RPM ever slightly at 70 mph, once the 34.1" tires are installed.

 

no need or want to...i'm happy with how it looks with 2" of lift and 265/75s. only reason i would step up is if i had the 4:56's to bring the ratio up just a bit. plus i have issues right how finding parking garages i can fit into as-is.

 

u should of got air bags lol j/p

 

I have my original 3.73 gears. I swapped in 4.88's at about 30,000 miles I think. I was going to throw them out but couldn't bring myself to do it. They are yours for the cost of shipping if want them.
Michael

 

riko what size tire are you running and do you tow with your setup? How do you like those 4.88's?

 

Is the rear axle w/limited slip? What sort of condition is the 4.10 truck? Are the fronts interchangeable or is the Dana 50 different from Dana 60(?) in the truck?

I don't know how the rear axle is put together...is the LS separate from ring/pinion? My Ex has LS in rear axle and I would want to retain that. The 4.10s would be perfect to allow 20" tires on my Ex.

Sorry, I'm pretty ignorant of how these axles are put together and what will interchange.

 

Good to know and thank you much for the offer! We are still in dealings with the 4:10 truck and it may be a little while yet. Please hang on to them for awhile.



The 4:10 truck is from AZ and has 9*,*** miles on it. I haven't seen the truck in person yet but it sounds very nice and very well taken care of.

Yes the LSD is separate from the ring and pinion. I just know this is the standard sterling 10.5" rear end, I don't know what axles the ring and pinion are compatible with besides the 10.5".

 

I tow at around 68 - 70 mph. Keeps me from getting run over on the interstates. I also have found that stock 3.73 axles with 265/75-16 tires keeps RPM at 2040 when running 70 mph. This seems to be a "sweet spot" for 6.0L.

When I try to tow at a lower speed, in theory to save fuel, I can't seem to get any better fuel economy by slowing down. What I think is that the transmission must downshift more often to get the engine back on the torque curve.

 

by judgeing by your sig. trying to get mpg slowing down might help but then i would prob to work harder on any slight inclines i think u need is:
to devert the air up so u wont be dragging the air straight into your camper or what ever i am trying to say here.