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View Full Version : Gear Swap & Speedo ?

snobrdrdan
02-18-2006, 10:58 AM
Okay....I know that everyone has said if you change the tire height you need to get the Speedometer reprogrammed/computer reflashed (whatever you wanna call it). I totally 100% understand that!

Now......I asked before (& searched) that if you only changed the gears that you don't need to get the speedo changed is what everyone says.

I asked the dealer & I got two different answers....that's why I'm asking again.

I had 3.55 open gears in my truck & I just got a 4.10 LSD put in.
I have the 545RFE 5 speed auto tranny (in my 2005 2wd w/ 4.7) and the parts guy told me that it's read off some sensor off the transmission?

And then the service dept. manager told me that it was off the differential??

I have no idea and honestly don't even remember what they told me, but neither of them knew for sure.
Then they said to reflash it would be $80 or something.


So is the speedo gonna read correctly or not??


And where does it read off of??
HemiDak
02-18-2006, 05:58 PM
They are both right. There are two sensors to provide accuracy. One in the transmission AND in the differential. The one in the differential reads off the ring gear, so the gear ratio won't matter. It will read the same as it did before the gear swap.
chris4x4
02-19-2006, 01:08 AM
What YellowKota2k said. Your speedo is gonna read accurate. :wave:
snobrdrdan
02-19-2006, 08:43 AM
That's what I thought since you guys (both of you) were the only people that I found (when I searched thru all the posts) that said it wouldn't matter with the gear swap

Thanks for saving me $80 :clap2: :biggthump
HemiDak
02-19-2006, 09:42 PM
No problem.
xtreme6669
02-20-2006, 02:38 AM
even if you had it flashed i dont think the dealer can adjust the pcm to any other settings than what were offered stock... or at least that is what i have heard
snobrdrdan
02-22-2006, 08:25 AM
Yeah I know....it would've just adjusted the speedometer reading

Oh well...I'm just glad I didn't waste $80 on nothing :biggthump
rayjj
03-06-2006, 10:37 PM
So how do you like the 4.10s compared to the 3.55s? Thats the same I wanna do just short on $$.
chris4x4
03-07-2006, 12:18 AM
So how do you like the 4.10s compared to the 3.55s? Thats the same I wanna do just short on $$.
Who are you asking? I LOVE mine. My truck gets a good tire scrub in second gear when taking off hard now. ( I have the 545RE trans). :drive: