Engine/Transmission (1994 - 1998) Differential Gear Change - speedo?

[JKing]

I'm having my ring and pinion (and carrier) changed from 4. 10 to 3. 54 next week. What will I have to do, if anything, to have the speedometer read correctly?



Jeff

 

[redram]

Change out the speedometer drive gear located in the tailstock of the transmission.

Should be about a 20 dollar part, 2 minute change.

 

[Boldt's Wagon]

Watch out for the trany oil bath when you pull the gear. Have the new one in hand and be quick. You can hold a piece of cardboard over the hole while you are fumbling around.

 

[JKing]

Isn't a '98 electronic that runs off a sensor on top of the differential?

 

[illflem]

Pretty sure JKing is right. You may have to have the dealer reflash it.

 

[Boldt's Wagon]

This is a 98 12 valve, did DC build a hybrid electronics for a 3 month production run? I would have guessed that the PCM etc would have been identical to the 97.

 

[JKing]

Everything about my 12V is the same as a 24V except for the motor. The instrument cluster is the same which leads me to believe it's the electronic setup.

 

[illflem]

What I heard happened is there was never supposed to be a '98 12 valve but Dodge had some left over 12 valve engines to get rid of...

 

[Andy Redmond]

1998 12 v's have the 98. 5 and newer speedo pickup, unlike the gear that's been in the transmission/transfer case.



You need a converter box with dip switches to "correct" the speedo reading.



Ratio right is the name as I recall. Rickson (the 19. 5 tire folks used to sell them).



About $150 if memory serves.



It's easy to install.

 

[JKing]

In case anyone's interested, there was no correction needed after the gear change.



The speedometer is about 2. 5 mph slow at 65 per my GPS which is the same as it was before the gear change. I attribute that to upsizing tires from 245s to 265s.