speedo

i have a 3b with 5.38 diffs and would like to get the speedo a little closer was the output gear different with4.27 diffs i have 33 in swamper so a gear from a higher gearset should help any have any ideas?

 

Sorry, but I gotta ask....does it really go fast enough to worry about it?

 

To answer your question, yes the speedo gear set in the transfer case was different for 5.38's vs. 4.27. I don't have the chart handy but I think Jpflat2a (Jim) has the charts and may be able to help (I got my charts from him).

 

yup it goes fast enough ,4.3 vortec engine 60 plus is ez,a little noisy with 33 swampers,and a lot spooky but i would like the odo to be correct for fuel milage checking,anf i drive on a well patroled mountain road with 40mph speed limit. and patrick hit on the real answer!
nicmil thanks i will see if i can send him a message

 

Assuming that the speedometer was accurate with the original tires, the change in speed indicated is proportional to the height of the tires; ie if you went from 28 inch tires to 33 inch tires, 28/33 = 0.85 or about 85% of your actual speed. The gear for 5.38s will have more teeth than the 4.27 gear by their ratios, 4.27/5.38 = 0.79 or 79% fewer teeth on the 4.27 gear. This is an over-correction, so that your speedometer would then read (0.85/0.79 = 1.07) 7% too fast.

 

Go to www.guageguys.com for your speedometer adapter.

 

vin thanks that is the solution to my problem.

 

i looked at electronic speedos but all i found were 140mph or 160mph a bit much for me if i could get an 80mph i would do that XX

 

Please tell us how it worked out. I only found that site after much research on the topic. I have a new set of 7.50 x 16 NDTs that I want to mount on my CJ-5, but I was concerned about the speedo issue. I'm interested to see the solution in action. Please advise. Uncle Vin