Change differential

jguevara1467 · 11-03-2009, 08:37 PM

Hello, I have a GMC Sierra 2000. I have six months that i have to change the differencial because it was not good anymore. I bought a differencial for a 2004 Sierra. Now when im driving my speedometer is 6 miles more than what im actually running. How can i fix this thanks/

bradrhale · 11-03-2009, 08:48 PM

wrong gearset or tire size. if you are using different size tires, return to the size you used before changing the diff. if not, then you used a different gearing than what you had before. if this is a 4wd, than you are headed for more devastation.

scavanger · 11-03-2009, 08:52 PM

Quote:

Originally Posted by jguevara1467

Hello, I have a GMC Sierra 2000. I have six months that i have to change the differencial because it was not good anymore. I bought a differencial for a 2004 Sierra. Now when im driving my speedometer is 6 miles more than what im actually running. How can i fix this thanks/

You need a speed sensor for the transmission to match the differential gears.

Scav.

hotrodpc · 11-03-2009, 09:17 PM

Quote:

Originally Posted by jguevara1467

Hello, I have a GMC Sierra 2000. I have six months that i have to change the differencial because it was not good anymore. I bought a differencial for a 2004 Sierra. Now when im driving my speedometer is 6 miles more than what im actually running. How can i fix this thanks/

Welcome to the fourm jgu, sounds like you got a lower geared differential. Correct me if I am wrong other members, but can't he just do a reprogram on his VSS to the ECM?

jguevara1467 · 11-04-2009, 05:16 AM

Thank you for the replying. The tire size is the same, i haven't change the tire size. I did change the diffrencial to a bigger one i think. My truck feels heavy on the first shift, and then very light on the rest of the shifts. Would changing my tires size fix this? Or i would have to reprogram the trucks computer?
Thanks

crabtruck · 11-04-2009, 05:43 AM

Welcome to the forum jguevara1467.

A quick call to the dealer would tell you if need program adjusted
or just a different sensor on trans output.

As brad mentioned above, simple if 2wd, problems if 4wd
because of mix-matched gearing. Which do you have ?

bradrhale · 11-04-2009, 06:45 AM

your first task before anything else is answering if this is 2wd or 4wd.
i dont believe changing the speed sensor in the tranny is going to work. it is not gear driven like the older trannies. one should be able to have the ECM reprogramed. but instead of letting a dealership do it for a couple of hunderd bucks, send it to a tuner and have a custom job done to enhance power output of the engine. you already have more than half the cost justified by not sending it to the dealer.

jguevara1467 · 11-04-2009, 05:59 PM

thank you for sharing information, my truck is a 2wd. I will call the dealer and ask. I think i might go with the custom tune for the ecm.
Again thanks

bradrhale · 11-05-2009, 07:00 AM

that is what i would do in your position. being 2wd, you should have absolutely nothing to worry about messing up. let us know what you ultimately decide to do and how it works for ya.

hotrodpc · 11-05-2009, 08:28 AM

Quote:

Originally Posted by bradrhale

your first task before anything else is answering if this is 2wd or 4wd.
i dont believe changing the speed sensor in the tranny is going to work. it is not gear driven like the older trannies. one should be able to have the ECM reprogramed. but instead of letting a dealership do it for a couple of hunderd bucks, send it to a tuner and have a custom job done to enhance power output of the engine. you already have more than half the cost justified by not sending it to the dealer.

Definately the way to go. Get a custom tune.While doing it they can also raise your governed max speed from 99mph and other performance enhancements also.

11-03-2009, 08:37 PM	#1
jguevara1467 Junior Member Join Date: Nov 2009 Posts: 3	Change differential Hello, I have a GMC Sierra 2000. I have six months that i have to change the differencial because it was not good anymore. I bought a differencial for a 2004 Sierra. Now when im driving my speedometer is 6 miles more than what im actually running. How can i fix this thanks/

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11-03-2009, 08:48 PM	#2
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	wrong gearset or tire size. if you are using different size tires, return to the size you used before changing the diff. if not, then you used a different gearing than what you had before. if this is a 4wd, than you are headed for more devastation.

11-04-2009, 05:16 AM	#5
jguevara1467 Junior Member Join Date: Nov 2009 Posts: 3	Thank you for the replying. The tire size is the same, i haven't change the tire size. I did change the diffrencial to a bigger one i think. My truck feels heavy on the first shift, and then very light on the rest of the shifts. Would changing my tires size fix this? Or i would have to reprogram the trucks computer? Thanks

11-04-2009, 05:43 AM	#6
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,366	Welcome to the forum jguevara1467. A quick call to the dealer would tell you if need program adjusted or just a different sensor on trans output. As brad mentioned above, simple if 2wd, problems if 4wd because of mix-matched gearing. Which do you have ?

11-04-2009, 06:45 AM	#7
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	your first task before anything else is answering if this is 2wd or 4wd. i dont believe changing the speed sensor in the tranny is going to work. it is not gear driven like the older trannies. one should be able to have the ECM reprogramed. but instead of letting a dealership do it for a couple of hunderd bucks, send it to a tuner and have a custom job done to enhance power output of the engine. you already have more than half the cost justified by not sending it to the dealer.

11-04-2009, 05:59 PM	#8
jguevara1467 Junior Member Join Date: Nov 2009 Posts: 3	thank you for sharing information, my truck is a 2wd. I will call the dealer and ask. I think i might go with the custom tune for the ecm. Again thanks

11-05-2009, 07:00 AM	#9
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	that is what i would do in your position. being 2wd, you should have absolutely nothing to worry about messing up. let us know what you ultimately decide to do and how it works for ya.