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TECHNICAL INFORMATION

Axle Ratio/Tire Size Calculators

**For Jeep or Chevy Technical Info see bottom of page

Okay, so you've torn your pumpkin apart and have the ring gear and pinion gear teeth count. This calculator will give you the gear ratio, just plug in the numbers.
  Ring Gear/Pinion Gear Teeth to Gear Ratio
Ring Gear Teeth Count: / Pinion Gear Teeth Count: Gear Ratio:
Ever wonder how far off your speedometer is with your new bigger tires? I'm using a simple ratio calculation, so this info will only approximate your corrected speed and depends on the accuracy of tire size diameters (assumimg nothing but tire size has changed).
  Speedo converter
Original Tire Diameter:
New Tire Diameter: 		Speedometer Reading (MPH): Corrected Speed (MPH):
Now that you have your truck lifted, you want bigger meats. They look cool and have the potential of being very functional, but they may also be robbing you of power/gas mileage. This calculator will get you back to a ratio that's closer to your original. Enter the values on the left and press Compute.
  Find new Gear Ratio with new tire size
New Tire Diameter:

Old Tire Diameter: 		Current Gear Ratio: New Gear Ratio:
Ever wonder what your low-low-low gear ratio is, your "crawl ratio"? You'll need to do a little research by finding out the transfer case and transmission ratios first. Enter your values on the left side, press Compute and your answer will be on the right.
  Find Overall Crawl Ratio
Transmis Ratio: TransCas Ratio: Axle Ratio: Overall Ratio:
I've spend a bunch of time trying to WAG (wild ass guess) my actual MPH when going down the road. By knowing your gear ratios and tire size you'll get a more accurate idea here. Enter the value on the left, press Compute.
  Find MPH
RPM: Tire Diameter:

Axle Ratio: Transmis Ratio: TransCas Ratio: 		MPH:
I suppose if you don't have a tachometer you could use this form, otherwise it's only useful to find out how accurate your Tach is. Enter the values on the left, press Compute.
  Find RPM
MPH: Axle Ratio: Transmis Ratio: TransCas Ratio:

Tire Diameter: 		RPM:
This formula is a nice way to get the tire diameter of those metric tires that are common on just about everything stock. For example a 265/75R16 would be around 31.6 inches tall. Enter the numbers into this form in the order you read them from the tire and press Compute.
  Convert P-Metric tire to Tire Diameter inches
Example: 195/75R15
/ R 		Tire Diameter:

These calculators were created and copyrighted by Mark I. Medina.

Please visit his home page: 4LO.com.



This calculates the amount of torque applied to the axle shafts. (Efficiency factor of 0.90 applied)
  Axle Torque
Engine Torque: 1st Gear Ratio: T-Case Ratio:
Axle Ratio: 		Axle Torque (ft-lbs):


Jeep 4x4 Technical Information

Jeep Transfer Case Info

Transfer Case Model

4 Wheel Drive Mode

Drive

Low Gear Ratio
Dana 300 ('80-'86) part-time gear drive 2.62:1
Spicer/Dana 20 part-time gear drive 2.03:1
Spicer/Dana 18 (early-'71) part-time gear drive 2.42:1
Borg-Warners 13-39
Quadra-Trac ('76-'79 CJ7)		 full-time chain drive 2.57:1
NP231/NVG231 part-time chain drive 2.72:1

Jeep Transmission Gear Ratios

 Transmission 

1st Gear

2nd Gear

3rd Gear

4th Gear

5th Gear

Reverse
AX-15 3.83 2.33 1.44 1.00 0.79 4.22
T5 4.03 2.37 1.50 1.00 0.86 3.76
T18A 6.32 3.09 1.69 1.00 ---- 7.44
T18 4.02 2.41 1.41 1.00 ---- 4.73
T4 4.03 2.37 1.50 1.00 ---- 3.76
T-176 3.52 2.27 1.46 1.00 ---- 3.52
T-150 2.99 1.75 1.00 ---- ---- 3.17
T15 3.00 1.83 1.00 ---- ---- 3.00
TH 400 2.48 1.48 1.00 ---- ---- 2.08
T14 3.10 2.61 1.00 ---- ---- 3.10

Chevy 4x4 Technical Information

Transfer Case Info.

See Transfer Case Properties chart at the bottom of this page to find out about your transfer case.

 

CHEVY BLAZER TRANSFER CASE IDENTIFICATION

Years

Transmission Type

Transfer Case Model

Notes
1969-1973 Automatic NP205
1969-1974 Manual Spicer 20 NP205's also used
1973-1979 Automatic NP203
1975-1979 Manual NP205
1980-1991 All NP208
1992-1993 All NP241


GMC JIMMY TRANSFER CASE IDENTIFICATION

Years

Transmission Type

Transfer Case Model

Notes
1970-1972 Automatic NP205
1973-1979 All NP203
1973-1974 Automatic NP205 Optional
1975-1979 Automatic NP205
1980-1991 All NP208 NP241 also used

Transfer Case Properties

Transfer Case Model

4 Wheel Drive Mode

Drive

Low Gear Ratio
NP203 full-time chain drive 2.00:1
NP205 part-time gear drive 1.96:1
NP208 part-time chain drive 2.61:1
NP241 part-time chain drive 2.72:1
Spicer 20 part-time gear drive 2.03:1


Transmission Gear Ratios

 Transmission 

1st Gear

2nd Gear

3rd Gear

4th Gear

5th Gear
SM420 
4-speed manual		 7.02 3.57 1.70 1.00 ----
SM465 
4-speed manual		 6.55 3.58 1.57 1.00 ----
TH350 3-speed automatic 2.52 1.52 1.00 ---- ----
TH400 3-speed 
automatic		 2.48 1.48 1.00 ---- ----
700-R4 4-speed 
automatic('82-on)		 3.06 1.63 1.00 0.70 ----
NV4500 GM   5-speed manual ('93-94) 6.34 3.44 1.71 1.00 0.73
NV4500 GM,DODGE 5-speed manual ('95-up V8 Trucks) 5.61 3.04 1.67 1.00 0.73


Axle Strength Based on Material and Size

 Size 

Material

Yield Torque

Axle Model
1.10-inch 1040 carbon steel 3,550 lbs-ft front D44, front GM 10-bolt
1.11-inch 1040 carbon steel 3,640 lbs-ft D30(27-spline), D35(27) rear,
8.25(27) rear
1.18-inch 1040 carbon steel 4,389 lbs-ft Ford 7.5-inch 28-spline
1.19-inch 1040 carbon steel 4,484 lbs-ft D60(30) full-float
1.20-inch 1040 carbon steel 4,643 lbs-ft Ford 9inch(28) rear, GM 7.63,
GM 8.5(28) (10 bolt)
1.21-inch 1040 carbon steel 4,706 lbs-ft AMC-20, Chrysler 8.25(29) rear
1.25-inch 1040 carbon steel 5,206 lbs-ft D60(30) front, D50(30) front,
D44(30) rear, GM 8.5 and 8.6(30)
1.29-inch 1040 carbon steel 5,707 lbs-ft Ford 8.8(31) rear, Ford 9inch(31),
Chrystler 9.25(31)
1.34-inch 1040 carbon steel 6,394 lbs-ft GM 10.5 (14 bolt) full float
30-spline
1.36-inch 1040 carbon steel 6,699 lbs-ft Ford 10.25 and 10.50 rear
full float 35-spline
1.37-inch 1040 carbon steel 6,828 lbs-ft D60HD rear full float 35 spline,
D70 rear full float 35-spline
1.42-inch 1040 carbon steel 7,619 lbs-ft GM 9.5 (small 14 bolt) rear
semi-float 33-spline
1.45-inch 1040 carbon steel 8,097 lbs-ft D60 rear semi-float 35-spline
1.46-inch 1040 carbon steel 8,283 lbs-ft Ford 10.25 rear semi-float
35-spline


Common U-Joint Strength Rating in Pounds-Feet

 Spicer Series 

Max Continuous

Short Duration

Short at 15 degrees
1310 130 795 765
1330 148 890 857
1350 206 1240 1193
1410 250 1500 1443


NP205 BASIC INFO
The NP205 is a gear driven part time transfer case. It can be operated in either two or four wheel drive. The overall length of the NP205 case is 12"-13" from the face of the case to the rear output yoke's center on fixed yoke models. The shift positions of the NP205 are as follows from the most forward position (towards the engine) to the rear most position: Four Wheel Drive Low Range, Neutral, Two Wheel Drive High Range, Four Wheel Drive High Range When in Two Wheel Drive, the NP205 does not turn the front driveshaft. The NP205 has a high range of 1.00:1 and a low range of 1.96:1. The NP205 has a fill hole for lubrication in the rear face of the case under the rear output shaft. The drain plug for the NP205 is on the rear face of the case on the lowest part of the case. The NP205 uses 80w-90 gear oil for lubrication. The NP205 has a three bolt cover over the idler shaft. This is one of the identifiable traits of the NP205. The shift linkage of the NP205 Is not adjustable. It operates on a simple lever with few parts. The NP205 case is one piece of cast iron. All of the working parts are in this single housing. The identification tag of the NP205 is located above the front driveshaft output The NP205 was available from 1973 to 1991. The NP205 holds 2.5 qts. prior to 1980.