Wht's my speed?

[cdlongjr]

I think we decided I have 373 gears w/ 31 inch tires. Is there a formula to guesstimate my actual speed? How would I go about correcting the speedo?

 

[Old Dog]

you will need a new speedo gear for the transfercase.
Good luck finding one, I found mine on e-bay. Been so long ago I don't remember where though. (old timers,you know)
There is a way to figure it out but I don't know how for sure, Maybe someone else does. Sorry

 

[CJ]

At 2224 RPM (assuming a 1:1 output ratio for your trans) you should be doing 55MPH

 

[Petescj]

Spoken like a true engineer.

At 2224 RPM (assuming a 1:1 output ratio for your trans) you should be doing 55MPH

 

[cdlongjr]

If I only had a tach! Another for the wish list.

 

[dalefan88]

If I only had a tach! Another for the wish list.

you can get one at any parts store for about $40. heres mine i work at advance auto.

click pic

 

[cdlongjr]

Re: What's my speed?

I'd like to find a factory tach, but thanks for the info.

 

[CJ]

If your looking for a factory tach - this is what it looks like. There are allot of places that sell replacements (they look pretty close to original).

Replacement tachometer - Shop sales, stores & prices at TheFind.com

Crown Automotive JEEP REPLACEMENT TACHOMETER : JC Whitney: Auto Parts & Accessories

 

[mylittlecj5]

for what I do, I'd rather have a Column-mounted tach. Its a lot easier to see while I am going down the road or the track.
I currently have a Sun tach, but will probably upgrade to one that matches the new guages when funds allow it.

 

[cdlongjr]

Trying to keep the 5 as original as possible, I forgot about "seing" the tach while driving. Good point about the column mount. I'll have to check the out.
Thanks!

 

[cdlongjr]

Got a column mount SunPro tach. Nice.
CJ,
ya sure about those rpms? My speedo will read 65+. I thought with larger tires, the speedo would read less.

 

[CJ]

A 3.73 gear with 31" tires with a 1:1 output ratio for the trans will be 2224 RPM at 55 MPH. With 33" tires at 55 MPH you would be turning 2089 RPM. With 28" tall tires at 55 MPH you should be turning 2462 RPM.

As tire size goes up, RPM drops for a given MPH.

I found a pretty good calculator for you... Engine RPM Calculator

 

[Old Dog]

Don't forget the tires probably aren't 31 in. Measure from the ground to the bottom edge of the wheel x2 and add the dia. of the wheel. measure the wheel it's probably 16 in to the outside of the rim.

 

[CJ]

That's very true - measure to be sure - the #s I gave are perfect world theoretical...

 

[cdlongjr]

I LOVE this site!