Speedo Error after Re gear

[scottmandu]

So before I get flamed to Search the F****ng archives.. I did. Several people asked this question on the high speed gears thread but there was no answer. After the re-gear (3.07 ring and pinion) the speedo is showing 20mph off at 50. GPS verifies a speed of 69 actual with the speedo reading ~50mph.

I did some research and found the speedo gets it's signal from the WTEC computer.. Which tells me there must be a setting or configuration variable in the TCM for the axle ratio. Is this something that an Allison dealer needs to program?

BTW I love these trucks!

 

[Suprman]

An a1 truck the cat dealer can plug in and reprogram. It may be possible for the allison dealer to to the first gen trucks. The trans diag plug is an older style I'm not sure if all dealers will have the setup to connect. It's my understanding that there are quite a few variables in the first gen trans control though.

 

[scottmandu]

My nearest Allison dealer says he can plug it up and read the settings. I just need to get the truck over there.

 

[Suprman]

Well at least you can get there a bit faster now.

 

[scottmandu]

Yeah something's still not right though.. GPS top speed shows to be 62mph.. so I'm not sure if I'm getting full rpm or full throttle.

 

[wehring]

Call me. Also in TX and have been through this. Can also read "Wehring LMTV upgrades" post. Have also hooked up cruise control and added 95hp and 71tq.

justin Wehring
979 997 3112

 

[Ukraine Train]

If the speedo signal is electronic then you can use a module to add a multiplier/divider to the signal. Dakota Digital makes these: http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/prd126.htm

 

[scottmandu]

If the speedo signal is electronic then you can use a module to add a multiplier/divider to the signal. Dakota Digital makes these: http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/prd126.htm

I saw that. That is option #2 if the configurations can't be changed in the TCM.