Speedometer reading way off???

**camarolvr69** · 08-19-2007, 04:12 PM

Lately I have noticed that my rpms seem off for the speed I am going.

I was driving on Quantico Marine Base the other day, and the MP's had one of those radar signs set up that tell you the speed limit and how fast you are going. So I drove by it and my speedo said 48, the speed limit was 40, and the radar thing said I was going 55.

I thought that was odd, so I had my dad drive beside me at 55 to check my speedo, and mine still read 48 while he was going 55.I also noted that at 60mph, I was exactly at 2k rpm.

I have a 97' z28 with the stock 2.73 gears and I installed a CPT trans. back in June. I also have a Trifecta Performance Mail-Order Tune.

Idk if the speedo sensor mounted on the trans could be off or what.

Any help would be greatly appreciated.

**greatwhiteZ28** · 08-19-2007, 04:41 PM

well there is a fix for that, remove everthing to the guage cluster ( like about to install some white guages) then pop off the speedo needle from when the car is on the off postion and set it back like a 1/8 of inch. (LEFT)

this may take a few times but have a buddy drive next to you till its dead on. but to make the adjustments easier dont install the lens and everything after adj.s just have the cluster poped in soo needle is easy to pop off

hope this helps you

**camarolvr69** · 08-19-2007, 05:20 PM

But this wouldnt fix my problem would it?
I haven't messed with the cluster, and the speedo used to read correctly. I am thinking it has got to do with either the trans. or my mail-order tune, because the problem has been within the last 2 months which is within the same time frame.

**rbob93** · 08-19-2007, 05:56 PM

I don't know what's wrong with your car, but to fix it by repositioning the speedo needle is not the brightest move

**greatwhiteZ28** · 08-19-2007, 06:56 PM

Originally Posted by rbob93

I don't know what's wrong with your car, but to fix it by repositioning the speedo needle is not the brightest move

why wouldnt it be. spend couple hundred dollars to send it for recailbration or just do it the easy way.

ok put it this way. the car was reading right before the mail in tune +, etc of stuff. soo its off, OK, and for 2 months now and still off. it aint going to change with out some kind of cailbration. soo if he doent want to spend big money on cailbration. why would this be the brightest move. this is free and if the problem aint going no where.......

its just like when people i know after installing some guages and they forget to make a picture of what there guages looked like before removing the needles and when installed there way off. like 25-50mph. then that s were i come in and do this same process like given abouve to fix it.

**rbob93** · 08-19-2007, 08:36 PM

His tune could be off or the speedo sensor could be bad
Changing the speedo needle does not correct the problem, just the effect
I would find out what caused the problem first

**oneBADDz** · 08-19-2007, 08:58 PM

Originally Posted by greatwhiteZ28

why wouldnt it be. spend couple hundred dollars to send it for recailbration or just do it the easy way.

ok put it this way. the car was reading right before the mail in tune +, etc of stuff. soo its off, OK, and for 2 months now and still off. it aint going to change with out some kind of cailbration. soo if he doent want to spend big money on cailbration. why would this be the brightest move. this is free and if the problem aint going no where.......

its just like when people i know after installing some guages and they forget to make a picture of what there guages looked like before removing the needles and when installed there way off. like 25-50mph. then that s were i come in and do this same process like given abouve to fix it.

what if the computer is wrong about what speed it is actually doing as well? how will it know when to shift at WOT? how will it judge it's kickdowns?

**camarolvr69** · 08-20-2007, 07:24 AM

Originally Posted by rbob93

His tune could be off or the speedo sensor could be bad

Im thinkin that since I got a mail order tune they could have reused a tune from another car that had 3.23 or 3.73 gears...how do I check my speedo sensor?

**mbrownin** · 08-20-2007, 09:21 AM

Originally Posted by greatwhiteZ28

why wouldnt it be. spend couple hundred dollars to send it for recailbration or just do it the easy way.

ok put it this way. the car was reading right before the mail in tune +, etc of stuff. soo its off, OK, and for 2 months now and still off. it aint going to change with out some kind of cailbration. soo if he doent want to spend big money on cailbration. why would this be the brightest move. this is free and if the problem aint going no where.......

its just like when people i know after installing some guages and they forget to make a picture of what there guages looked like before removing the needles and when installed there way off. like 25-50mph. then that s were i come in and do this same process like given abouve to fix it.

Because chances are it's not off by the same mph everywhere. If it says 35 when he's actually doing 40, that's 5 off, but then it will say 70 when he's actually doing 80, which is 10 off. If he moves it to be "correct" when indicating 60, it will still be off at slower or higher speeds.

**greatwhiteZ28** · 08-20-2007, 04:45 PM

Originally Posted by mbrownin

Because chances are it's not off by the same mph everywhere. If it says 35 when he's actually doing 40, that's 5 off, but then it will say 70 when he's actually doing 80, which is 10 off. If he moves it to be "correct" when indicating 60, it will still be off at slower or higher speeds.

if the postion is correct and dialed in at any speed it dont matter how fast hes going, look this is a fix and could be a good one if he is leaving as is like said above.

**oneBADDz** · 08-20-2007, 05:18 PM

Originally Posted by greatwhiteZ28

if the postion is correct and dialed in at any speed it dont matter how fast hes going, look this is a fix and could be a good one if he is leaving as is like said above.

not if it's tuned for the wrong gear, it's off by a percentage, not a set MPH.

**mbrownin** · 08-20-2007, 07:39 PM

Originally Posted by greatwhiteZ28

if the postion is correct and dialed in at any speed it dont matter how fast hes going, look this is a fix and could be a good one if he is leaving as is like said above.

Sorry, that's just wrong. I'll bet money the faster he goes, the more mph he is off.

**camarolvr69** · 08-20-2007, 07:44 PM

I contacted Trifecta Perf. about my problem,heres what they said:

"Hi Jeff, looks like the calibration file we sent is for a 3.23 ratio car. I suspect the mistake occurred because your order came in before we were requiring VIN numbers for LT1 orders.

I’m going to go ahead and send out a tuner with the fixed ratio for you at no charge. I will need to secure the tuner with a deposit, however. I have your credit card number on file, so I’ll go ahead and use that unless you say otherwise.

Sorry for the inconvenience."

They are an awesome company. Shows they really care about their customers. Thanks guys for all your input.

**rbob93** · 08-20-2007, 09:43 PM

Great!!

**cocheesews6** · 11-19-2007, 07:34 PM

How was your tune before and after using Trifecta? Do you have any mods at the time of tuning and if so, was there a comparable differnce? I have been speaking with them, in the process of doing some bolt ons, and feel for the price, it should be able to get all I can get. Do you feel it was worth the value, thanks.

**camarolvr69** · 11-20-2007, 08:28 AM

Well I am only bolt-ons myself. The tune improved the SOTP feel, as well as tune out things like rear O2's, cats, !EGR, and !AIR. They do an awesome job imho.