Speedo Gears - Where To Find And What To Get?

Whelp, I'm lost.
I've been searching around on here for a solid answer on what gears I'll need, and I can't find it.

I have 4.88s and 33s. I've been told that OEM gears for a 4.27 equipped-Jeep will work well. Where can I find those? Is there another combo to get?

Most of the results I can find online show 26-42-ish tooth gears, which I'm assuming are not actually for a d18.

Quadratec has a chart on speedo gear teeth, but from what I've gathered, that is completely wrong.

*Edit*
Looks like 4.27 gears are 6 & 18 tooth gears. I'll see if I can find those around.

Question 2: Should I have a 6 tooth or 4 tooth gear stock on a '66?

 

The gears are hard to find. If your lucky some nos gear pop up on ebay. I gave up trying to find the correct gear combo and dealing with brocken cables that i went with a gps speedometer

 

https://www.kaiserwillys.com/produc...truck-station-wagon-fc-170-with-6-226-engine/
This looks right to my untrained eye, although it does not look good to my air-cooled debit card.
I may order this and a 6-tooth drive gear and be the test dummy.

 

Rather than try to find gears for my '71, I checked my speed against GPS to calculate the error.

Then went to ebay and searched for "speedometer gear ratio adapter" and found one that was the right ratio. https://www.ebay.com/sch/i.html?&_nkw=speedometer+gear+ratio+adapter

I also need a keyway to square adapter and a short cable because the gearbox hit the back of the transfercase.

All the parts:


Keyway adapter https://camarostoreonline.com/products/speedometer-cable-adapter-key-c5887-camaro-store-online


Because this:


Short cable extention: https://www.summitracing.com/parts/dak-130011

And installed up inside the frame rail. Speedometer is with 1/2 mph now:

 

I need some measurements from the group for the entire assortment of gears.

I'll give it a go on the old southbend

 

Interesting. How much $$ did that run you roughly?

 

Sorry? I think I'm too much of a young'n to understand...

 

About $100 when all was said and done. So not cheap, but perfectly calibrated. Another nice benefit is being able to re-gear really easily if I change gear ratios or tire sizes in the future. Just need to buy a new gearbox.

 

Alright. Just a smidgen more than the gears from KW then.

 

Also note there are a couple of series of drive gears in the tail housing and the driven gear needs to match the drive gear. Just because it has the right tooth count doesn't necessarily mean it will work.

I found this chart on some Jeep forum or another. Using the part numbers in this chart will help you search ebay and other places for the right gear. Sometimes you'll have better luck searching for the Stewart Warner part number:

DANA 18 SPEEDOMETER GEAR CHART

JEEP part #.......SW part #.........teeth.......final drive ratio.......years.......models

A-1511............447021............4............Drive Gear.............41-71........MB / GPW / M38 / M38A1 /
A-5707............448110............15.............4.88.................41-45........MB / GPW /
A-5707............448110............15.............5.38.................45- 71.......M38 / M38A1 /

///////////////////////////////////////////////////////////////////////////////////////////////

A-1511............447021............4............Drive Gear.............45-62........CJ / with 134 engines
A-5707............448110............15.............5.38.................45-62........CJ / with 134 engines

///////////////////////////////////////////////////////////////////////////////////////////////

642830............447096............4............Drive Gear.............47-57........SW / PU / FC / with 134 engines
642830............447096............4............Drive Gear.............54-57........SW / PU / FC / with 226 engines
643710............xxxxxx............13.............4.88.................54-57........SW / PU / FC / with 226 engines
644118............448162............15.............5.38.................47-57........SW / PU / FC /with 134 engines
644421............xxxxx.............xx..............xxx.................xx-xx........xxxxxxxxx

///////////////////////////////////////////////////////////////////////////////////////////////

910086.............447331...........6............Drive Gear.............58-71.........CJ / SW / PU / FC / with all engines
xxxxxx.............448361...........15.............3.73 ?...............xx-xx.........xxxxxxxxxxx
910087.............448493...........18.............4.27.................62-??.........CJ with 134 engine
910088.............448494...........20.............4.88.................58-62.........SW / PU / FC with I-6 226
910088.............448494...........20.............4.88.................66-??.........CJ with 225 engine
910089.............448495...........22.............5.38.................66-71.........CJ with 134 engine

///////////////////////////////////////////////////////////////////////////////////////////////

931381.............447537............6............Drive Gear.............6?-71.........CJ with 134 + 225 engine ?
931381.............447537............6............Drive Gear.............63-64.........SW / PU with 230 engine
931382.............448855............15.............3.53.................63-64.........SW / PU with 230 engine.
931383.............448856............16.............4.09.................63-64.........SW / PU with 230 engine
931384.............448857............17.............4.27.................63-64.........SW / PU / with 230 engine
931385.............448858............18.............4.89.................63-64.........SW / PU / with 230 engine
931384.............448857............17.............4.27.................6?-71.........CJ / with 134 engine
931385.............448858............18.............4.89.................6?-71.........CJ / with 225 engine

You can only use the driven gears in each section with the drive gears at the top of the section.

This bit me on my '71. I rebuilt and installed a transfercase that came from a Jeep with 4.88s not realizing it had a different drive gear than the stock 3.73 setup, I could not find any driven gear to get to 3.73. Some had the right tooth count, but weren't compatible with the drivegear I already had.

Since the transfercase was freshly rebuilt with pre-loads set, I didn't want to pull it apart to swap the drive gear and went with the gearbox instead. Plus I plan on re-gearing the Jeep some day and it gives me more flexability.


If you go the gearbox route, this PDF is really helpful listing different manufacturer gearbox part numbers for different ratios: http://clarkbrothers.net/pdf/SC795_Catalog2_Page_5to7.pdf

 

Thank you. I believe KW also sells a 6-tooth drive gear which I'd probably order as well if I go that route. I've seen some 4-tooth drive gears as well, so I would rather get the correct piece the first time.

 

With enough information the gears and maybe additional custom ratios could be made.

 

I too run a free cell phone app for my speedo(s). My truck was off as well. Lucky, I could calibrate that one electronically. for the CJ and the Bronco, it's the cell phone.

 

"I'll give it a go on the old southbend." = "I'll try to make the correct gear on the South Bend lathe."