upgrade for 4l80e maybe?

[99xcss4]

My truck with 33s and a 4.10 hits 2000 RPM at 62mph. This is the same as your calculation with 37s and a 4.88. You're still giving up more than I am swinging all that meat around, so I wouldn't go any less than a 4.88 to try and breathe some life back into that thing.

I am going to take your advice when the time comes I do not want to have to do it more than once because I was unhappy the first time thanks

 

[99xcss4]

I have question when I do the re-gear it shows available for the 9.25 ifs normal and reverse rotation what do I need the front-end is from a 92 k2500 suburban https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending I do not think I will have any problems finding what I need for the 14 bolt that also came from the suburban. I had read that truck rear axles and suv reear axles are not the same width but I had no problem doing the swap

 

[RDF1]

can you explain what tayto is talking about with the lockup rpm drop and what do the numbers represent in the 1000 to 6500 rpm range on the carts is have post that is what is going over my head

I wouldnt worry about the lockup/unlock. As that would change by power output and final gear ratio.
Very few calculators account for the convert unlocked becuase it will be different with every setup.

The formula for this whole ordeal is this:

(RPM x Tire Diameter Inches) / (Final Drive Ratio x Transmission Gear Ratio x 336)
So if you have 37" tires, 4l80E, and 4.10 gears
You would be 1955 rpms at 70mph There is zero slip included in this. Meaning no converter slip nor clutch slip.
Basically your a little under factory final ratio with stock size tires.
And remember lifting the truck with larger tires means less aerdynamic brick wall you pushing down the road so it will need more power. Lower rpms means less power.



37" 4L80E 4.88s
2000 rpms 60mph
2160 rpms 65mph
2327 rpms 70mph
2500 rpms 75mph
2650 rpms 80mph

37" 4L80E 5.13s
2100 rpms 60mph
2275 rpms 65mph
2450 rpms 70mph
2620 rpms 75mph
2800 rpms 80mph


Compared to my 2500HD the calcualtor shows this:

33" 4L80E 4.10s
1880 rpms 60mph
2035 rpms 65mph
2200 rpms 70mph
2350 rpms 75mph
2500 rpms 80mph
I rarely ever go over 70mph and with GPS and speedo calibrated the rpms are actually 2300.

 

[99xcss4]

(RPM x Tire Diameter Inches) / (Final Drive Ratio x Transmission Gear Ratio x 336)

what dose the 336 represent

 

[L31MaxExpress]

I wouldnt worry about the lockup/unlock. As that would change by power output and final gear ratio.
Very few calculators account for the convert unlocked becuase it will be different with every setup.

The formula for this whole ordeal is this:

(RPM x Tire Diameter Inches) / (Final Drive Ratio x Transmission Gear Ratio x 336)
So if you have 37" tires, 4l80E, and 4.10 gears
You would be 1955 rpms at 70mph There is zero slip included in this. Meaning no converter slip nor clutch slip.
Basically your a little under factory final ratio with stock size tires.
And remember lifting the truck with larger tires means less aerdynamic brick wall you pushing down the road so it will need more power. Lower rpms means less power.



37" 4L80E 4.88s
2000 rpms 60mph
2160 rpms 65mph
2327 rpms 70mph
2500 rpms 75mph
2650 rpms 80mph

37" 4L80E 5.13s
2100 rpms 60mph
2275 rpms 65mph
2450 rpms 70mph
2620 rpms 75mph
2800 rpms 80mph


Compared to my 2500HD the calcualtor shows this:

33" 4L80E 4.10s
1880 rpms 60mph
2035 rpms 65mph
2200 rpms 70mph
2350 rpms 75mph
2500 rpms 80mph
I rarely ever go over 70mph and with GPS and speedo calibrated the rpms are actually 2300.

Your 2500HD is geared almost identically to my Express. At 70 mph here you would be a grille emblem on a Peterbuilt 379 or Kenworth. I was running 75-85 mph on my way home this morning, mostly in the right lane and still had a numerous semis pass me as well as almost everything else on the road. I had the cruise set at 83 mph (2,500 rpm) for alot of it and I have enough power reserve that driving into a 15+ mph head wind with gusts close to 30 mph I was not only holding lockup but also still in lean cruise at 15.5-16:1 on the flats. Converter unlocked on a few grades and had the engine spinning 2,800-3,000ish with 400-500 rpm of slip but locked right back up when I hit the top. My fuel economy math was showing a 14 mpg estimate which is much lower than normal but not unexpected considering the conditions on the trip shoving a brick into a 100+ mph wind. I was hitting and holding load cells on the VE table that are only normally touched on moderate acceleration. The trip would have been miserable with less gear although a 6L90E is in my future. 5th gear in the 6L90E would have been great, a little more rpm but alot less engine load.

 

[99xcss4]

well high psi fuel system 454 tbi makes around 250hp net at the crank and 410 ftlbs net at the crank seeing as the truck was born a diesel and swaped to gas you could say some thing that are normally equipted on a gas truck magically fell off on a trip to mexico so maybe a very small power bump I do not have my hopes up though I only plan on doing minor mods maybe a bit closer to 260hp and a bit closer to 415 ftlbs to the engine with 3 body lift 6 suspension lift with what apeers to be a very heavy home-made grill guard and 37x12.50x17 mounted on 17x9s and at least 4.88s I say at truck is an extended cab long bed I am expecting very poor mileage

 

[RDF1]

what dose the 336 represent

"The number 336, referred to as the constant, is a conversion factor that allows all the components in this formula to interchange between measurement units. Note that rotations per minute and miles per hour must be in the same measurement units. Basically, it brings the time measurements and the distance measurements together in a mathematically interchangeable fashion. The conversion factor starts with 1 mph equals 5,280 feet/mile and ends at 336 revolutions/minute. Revolutions/minute always cancel out with other units inside the equation."

 

[99xcss4]

cool thanks at least I am starting to learn some things that are very new to me

 

[RDF1]

Before you start spending any money give this a try.
Put your shifter in 3rd gear and drive around for a few days or a whole tank of gas.
If it pulls hills great and your happy with how it holds speed.
Then you got a idea on how it would normally act in overdrive with 5.13s within a few rpms of the 4.10s in 3rd.

4.10s 37s 3rd gear 1:1 70mph 2500rpms
5.13s 37s 4th gear 0.75:1 70mph 2450rpms

not to mention your added torque in the lower gears with 5.13s.

I have tuned some 6L80E (.67:1 6th gear) equipped trucks with 35" tires with 3.08 gears. Running 1350rpms at 70mph it was miserable. Told the kid either he needs gears, shorter tires or we can just lock it out of 6th gear. 95 mph is only 1850 rpms with that setup in 6th.

I ended up having to just raise the 5>6 shift point so high it never used 6th gear. 5th gear is .85 and it turned 1800 rpms at 70 and would pull most hills without unlocking TC or downshifting.

 

[99xcss4]

would I see any gains with 5.38s or is that too much gear