Speedometer is showing less than actual speed, help!

[UNDsioux]

Hi All,
Long time lurker, first time poster. I am having an issue with my speedometer, it reads slower than my actual speed. I sent the cluster off and had all of the motors repaired and calibrated with the correct tire size 265/70R17. I replaced the speed sensor located in the transfer case and still no luck. Below are some examples of what it's reading.
Speedometer is reading ///Actual Speed
20MPH----------------------------24MPH
37MPH----------------------------45MPH
48MPH----------------------------55MPH
54MPH----------------------------65MPH

Vehicle is a 2005 Tahoe Z71, 5.3L any ideas why the gauge is reading incorrectly?
Thanks!

 

[Slckls1]

did you change wheel/tire size? rear end gearing?

 

[UNDsioux]

Nope, original tire size. I am not original owner but I believe it's the stock rear end.

 

[Slckls1]

that's the only thing I can think of that would throw it off. I'm no expert, though!

 

[mdnitedrftr]

What are you using to read your actual speed?

 

[Tonyrodz]

Using a GPS to measure actual speed?

 

[UNDsioux]

Three different GPS speed apps, looking at the numbers it seems as if it's reading about 17% slower than actual speed. In past vehicles they have been off by about 3 mph at any speed. Could the previous owner install a tune that could change the accuracy?

 

[Rocket Man]

Three different GPS speed apps, looking at the numbers it seems as if it's reading about 17% slower than actual speed. In past vehicles they have been off by about 3 mph at any speed. Could the previous owner install a tune that could change the accuracy?

Yes, if he had the tune calibrate for different tires/wheels which he swapped out before he sold it. BB tuned my pcm for my 26" wheels, for instance.

 

[UNDsioux]

Yes, if he had the tune calibrate for different tires/wheels which he swapped out before he sold it. BB tuned my pcm for my 26" wheels, for instance.

Is there anyway to reset to factory without having a programmer?

 

[Rocket Man]

Is there anyway to reset to factory without having a programmer?

I don't know. I bought an Autocal so I have the original tune file that I can reinstall if needed. Most tunes are done differently though, since the Autocal is expensive. Plus there's many different tune companies and programmers. You should get ahold of a tuner like Black Bear and see if they can answer questions. They're very helpful.

 

[Chip18]

Hmm ... "this" seems to be the one question that is not here??? :

http://www.blackbearperformance.com/faqs.asp

It may very well have a different gear set in it??? People do "stuff" and don't document changes as a rule. Unless you get a big box of receipts for parts purchased, with a used vehical ...you have no idea what's been done if you can't see it??

You can calculate the ring gear ratio manually however. Never had a need to do so myself, but I think you'd pull the Diff cover, make a mark on the pinion gear and the right rear tire and count the number of times the tire rotates before the pinion gets back to where it started??

Or ... take it to a driveline suspension shop and ask them to check it out, but you'll need to know what is "suppose" to be in there first.

 

[Rocket Man]

I said to get ahold of Blackbear and ask them if they can help with questions about whether or not he has a tune installed, not look at a list of FAQ's that have nothing to do with his problem.

 

[Chip18]

I said to get ahold of Blackbear and ask them if they can help with questions about whether or not he has a tune installed, not look at a list of FAQ's that have nothing to do with his problem.

And I was "not addressing" "your" "answer" that's what "quotes" are for ... just saying.

 

[Rocket Man]

You quote everything. I was just stating your "help" was along the same lines as mine however it was "unhelpful". Leave it at that @Chip18 . You seem to be following my every post in every thread lately. I'm feeling "stalked". LMFAO. Quote that.

 

[Chip18]

You quote everything. I was just stating your "help" was along the same lines as mine however it was "unhelpful". Leave it at that @Chip18 . You seem to be following my every post in every thread lately. I'm feeling "stalked". LMFAO. Quote that.

Well ... "I thought I addressed" the "what gear ratio does this vehical have, issue???" And I found it "interesting" that there was no mention of wheels and tires under the BB FAQ???

And stalking you??? Well not sure if that is an insult or a compliment?? Nonetheless it's not my style! So yeah ... "sorry if I gave you that impression???"

 

[Rocket Man]

Well ... "I thought I addressed" the "what gear ratio does this vehical have, issue???" And I found it "interesting" that there was no mention of wheels and tires under the BB FAQ???

And stalking you??? Well not sure if that is an insult or a compliment?? Nonetheless it's not my style! So yeah ... "sorry if I gave you that impression???"

I thought you explained what quotes were for! I think you're abusing those little fellas!!! The gear ratio had already been discussed. We were moving on. BlackBear's FAQ's are just that- FREQUENTLY asked questions. That's why I suggested he actually talk to them. He has a problem that doesn't come up frequently. And I'm just messing with ya about stalking....maybe.

 

[Chip18]

I thought you explained what quotes were for! I think you're abusing those little fellas!!! The gear ratio had already been discussed. We were moving on. BlackBear's FAQ's are just that- FREQUENTLY asked questions. That's why I suggested he actually talk to them. He has a problem that doesn't come up frequently. And I'm just messing with ya about stalking....maybe.

LOL ... you got me!! I've been accused of "abusing" "quotation" marks and "exclamations" mark in the past on a few other boards.

As for the gear sets??? Near as I can tell ... the "OP" has no idea what the gear ratios are??? Used vehicle ... one has no idea what has been done to it??? They might be the stock ratios, they may not be???

One would have to change front and back as I understand it with AWD/4 WD?? A lot of work but "maybe" someone did it??? "Now" he knows ... that it can be checked.

As for BB "FAQ" and that particular question "not" showing up ... perhaps "Wheels and Rims" is a question they ask first ... so no one has to deal with it?? Don't know???

Sorry if I get on your last nerve ... not my intent.

 

[Rocket Man]

It's cool @Chip18 , no worries. I think you're more amusing than annoying. Most times, that is!

 

[UNDsioux]

Thank you all for the reply's, the cluster makes a lot of clicking noises and there is a sticker on the back that says refurbished so it looks like the previous owner had issues as well. My dad has a 2003 Avalanche, I will swap mine with his and see if his is accurate in my Tahoe. I have read online that the clicking noise is from the old motors but all were replace so I don't know where it's coming from, if the cluster is unplugged the noise goes away, or if it's plugged in the noise only occurs when the engine is running.

 

[fiatdale]

Procomp makes a speedometer calibrator solely for tire size / gear changes, its slightly cheaper than a programmer. Sounds like your cluster may be bad to begin with. Stepper motors arent hard to replace if you know how to solder, so that may be a cheap option to look into.