Speedometer Off

L

LURKER99

Carolina Marauder Member
I have a 03 300A @ 60k, I bought the MM used a little over a year ago @ 34k. When I bought it I noticed my speed was off by 10mph, if the speedometer read 80mph then I'm only going 70mph. My tire size is still at factory standards, the only thing I could come up with is that I could possibly have 4:10s already installed from previous owner and they just didn't get it tunned for the 4:10s! I plan to check the driveshaft this weekend for the 4:10s but if it's not that, any suggestions or has anyone else out there had this problem?? Thanks
:beatnik:
 
I cannot remember how much the speedo was off with gears as it has been sooo long ago now.

I do remember driving it with the gears newly installed and mailing my chip to DR to have it corrected.
Every time I went WOT from a dead stop it would bang off the rev limiter going into 2nd.

I know it's not healthy, but if you do have gears and weren't tuned for them, this has a good possibility of occuring.
 
CRUZTAKER said:
I cannot remember how much the speedo was off with gears as it has been sooo long ago now.

I do remember driving it with the gears newly installed and mailing my chip to DR to have it corrected.
Every time I went WOT from a dead stop it would bang off the rev limiter going into 2nd.

I know it's not healthy, but if you do have gears and weren't tuned for them, this has a good possibility of occuring.
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I haven't really came out the hole that strong yet I smoked it out a few times. I have tried to take it easy until I find out whats wrong with it. I just had the rear end assembly replaced lol!!!:P
 
LURKER99 said:
Just the axles both sides .....
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No problem, go pound on it and find out.

Get on an on-ramp and from a first gear slow roll and OD off pound it through to the 2nd shift. Watch the tac and see what happens.
If you have 4:10's and no tune for it, you should hit the limiter.

She'll forgive you. Just take her out for ice cream afterward.:P
 
It could be something other than 4.10s too. I personally installed 3.73s in my MM and know of at least one other MM w/ 3.73s. There are some 3.90 cars out there as well...

Although someone who would install gears and no tune....well never mind what I think about that
 
CRUZTAKER said:
No problem, go pound on it and find out.

Get on an on-ramp and from a first gear slow roll and OD off pound it through to the 2nd shift. Watch the tac and see what happens.
If you have 4:10's and no tune for it, you should hit the limiter.

She'll forgive you. Just take her out for ice cream afterward.:P
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Oh ok sounds like fun, she better forgive me I spoil her everyday lol!! On that note is it going to really hit the limiter or its going to be close????:confused:
 
VicsEvilBrother said:
It could be something other than 4.10s too. I personally installed 3.73s in my MM and know of at least one other MM w/ 3.73s. There are some 3.90 cars out there as well...

Although someone who would install gears and no tune....well never mind what I think about that
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Humm good info. Yes I agree about the "no tune" :bs:lol. You put yours in

your self huh???? Also you are right down the road in Fairfax VA. I think we need to PM:bows: for futher info. Also what tuner did you go with I was thinking of going with the X-Cal. 3????:beer:
 
I bought the dealer OTC/Rotunda tool and I have a shop press. I installed the gears in my apt. garage across from the Springfield mall. I have 3 cars and 2 private garages out here.
 
LURKER99 said:
I have a 03 300A @ 60k, I bought the MM used a little over a year ago @ 34k. When I bought it I noticed my speed was off by 10mph, if the speedometer read 80mph then I'm only going 70mph. My tire size is still at factory standards, the only thing I could come up with is that I could possibly have 4:10s already installed from previous owner and they just didn't get it tunned for the 4:10s! I plan to check the driveshaft this weekend for the 4:10s but if it's not that, any suggestions or has anyone else out there had this problem?? Thanks
:beatnik:
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This is easily fixed with a tune
 
CRUZTAKER said:
You really need to find out what is going on before you "fix" anything.;)
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I have a 03 300A @ 60k, I bought the MM used a little over a year ago @ 34k. When I bought it I noticed my speed was off by 10mph, if the speedometer read 80mph then I'm only going 70mph. My tire size is still at factory standards, the only thing I could come up with is that I could possibly have 4:10s already installed from previous owner and they just didn't get it tunned for the 4:10s! I plan to check the driveshaft this weekend for the 4:10s but if it's not that, any suggestions or has anyone else out there had this problem?? Thanks

I would bet this is a safe assumption, the owner probably turned the car back to stock, and the car has 4:10's to confirm this put a white mark on the drive shaft, and the rear tire count the turns, and do the math.
 
LURKER99 said:
Just the axles both sides because the driver side bearing seal went bad as always on my model, so they replaced both axles and serviced the diff. it was just the TSB kit.
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What was the symptom of the bad bearing seal? Leaking? Squeeking? Something worse? :confused:
 
LURKER99 said:
my speed was off by 10mph,
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No such thing. Speed can't be off by an even amount. Are you going 0 and it says 10?! It's off by a proportion, often stated as an amount per 10mph.

4.10's will put you off at about 1.5mph per 10mph. If you are actually going 70, speedo will say 80.5. (1.5/10 x 70 + 70) or (70x1.15)

Test in 3rd (OD off) on the highway at 70 since this is 'straight through' 1:1 ratio in the trans.

4.10 rpm should be 3463
3.55 rpm should be 2999
3.73 rpm should be 3151
4.30 rpm should be 3632
 
You can also use an online gear calculator (similar to the spreadsheet), with the following information:

Revolutions per Mile = 724 (Stock)
Redline (RPM) = 6000
First Gear = 2.84
Second Gear = 1.55
Third Gear = 1.0
Fourth Gear = 0.7

Note your RPM at a fixed speed and vary the Axle Ratio value to determine what you have.
 
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