Speedo off 15mph

[66sprint6]

Just picked up a fairly nice 91 ranger 2.3l with a 5 speed from a buddy and got to work trackin down a couple loose ends last night. Its throwin a check engine light, and I got codes 33, 77 and 52 but both KOEO and KOER tests showed 11 meanin clear. I think I can track those issues down no problem, but somethin that is stumping me is that the Speedo reads 15mph faster than you are actually going verified with a GPS. Tires are 205/70/14 but Im not sure whether the rear gear is stock or not. Ide imagine so, but would like to check and see. The odometer seems to be spot on using mile markers on a 3 mile stretch, but again I will verify with my GPS later. The tach seems fine, all other gauges are workin except for the fuel level. Any ideas guys? I did some searching around on here and Google and couldnt come up with much so I thought Ide ask. I really appreciate the help!
Matt

 

[cammeddrz]

speedoes aren't off by a specific mph, it is a percentage, for example if it is 15mph off at 30 mph, then it would be 30mph off at 60mph make sense? if it is consistently 15mph off all the way through a range of speeds its not your speedo, its the handheld device that is using multiple orbiting objects that are several hundred thousand feet away as a reference while computing data to come up with a speed reading... there is a margin for error on those

 

[66sprint6]

Makes sense, but the issue still stands, its off consistently and when I checked it at 30mph speedo said 45 and when I checked it at 35 it said 50 etc. So in that specific range is was 15mph off roughly. I understand its a percentage, guess I shoulda cleared that up earlier. Im not worried how accurate the GPS is, Ide just like to get my speedo back in line if possible. This isnt my first rodeo, isny my first ranger either LOL but this is the first time Ive seen this on an otherwise stock vehicle. Only thing I can think of is if the rear gear was swapped by a previous owner. If anyone has anything else to look at Ide appreciate it!
Matt

 

[cammeddrz]

don't even take these readings to heart

between the motorcycle forums, boat forums, car forums, and truck forums this issue has popped up i can't count how many times. everyone is like "my gps says my speedo is off" for some reason people think that a gps is perfect

using any gps device as a speedo there is a huge chance the reading will be off.

get a cop, and get radarred. throw the gps away, or use it for what it is designed for a Global Positioning System, its not a PSMS.... Precise Speed Measurement System

 

[66sprint6]

Ok...hows this? In 1st/2nd gear in a 15mph zone just coasting Im doin 30-35mph easy according to my speedo. My 0-60 is like 3.5 seconds right now...HIGHLY doubt this 2.3 longbed is that fast. I dont care HOW off it is, it just IS. I was clocked by a cop this morning and nearly shat myself doin 45-50 in a 30 that they are strict to enforce. Cop didnt even look at me twice. I appreciate your posting, but I didnt come on here to ask how close my GPS was to actual speed, I asked why my SPEEDO isnt right. This is a RANGER forum, if I wanted to learn the most effective way to figure out HOW off my speedo was, ide go elsewhere. Fact is my speedo is wrong, period. What should I be lookin at other than finding a cop and not lookin at my GPS




Matt

 

[cammeddrz]

a swing and a miss....

 

[66sprint6]

The only one swingin and missin is you buddy. Im not here to argue, i simply asked a question. Im a newb here, yes, but I been around the block a time or 8 with these old Fords and Im certainly not stupid. I dont give a damn that my GPS may not have the exact speed, but I know for certain that my speedo is WRONG. Can you prove me wrong? Has anything you said done anything to aide in the fixing of said speedo? Nope, still broken. I didnt come on here to start an arguement with a smartass know-it-all. If I wanted to do that ida went to the freakin AutoZone. Instead I jumped on here hoping someone who knew a thing or two more than me or has experienced this exact issue might step in and say "Hey, check this out". Thanks anyways!
Matt

 

[press 1 for english]

Maybe this makes too much doggone sense but ride along someone with a good speedo and compare numbers.
I honestly don't know how people can survive without cell phones, internet, and gps. LOL!

 

[WTF]

Does your truck's current rear axle have the diff tag on it? There's a chart of the axle codes on this site's tech pages or you can do the old skool ballpark gear math by counting the d-shaft to tire spin thingy. Did your truck come stock wity 205s according to the door tag? I've never had an accurate speedometer in any of my B2s or Ranger but it's nice to have one that's close. Hope this helps!!

 

[66sprint6]

Press 1 for engrish...i said it once, ill say it again. im not on here to figure out HOW off the speedo is, just that it is...is that doggone clear enough for you? I lived without cell phones etc so dont gimme that bullshit. I figured since I had it with me ide check it out and see what was up.

WTF...I read the tag on the door and the tag on the rear end and the door says code 84 and the tag says 3 45 so it seems to line up unless the PO swapped gears. Also it says 215/70/14 but the tires on there now are only 205's. Im askin my buddy if he knows whether or not the gears may have been swapped before he bought it as we speak but I doubt it. If I cant get any info Ill try to figure it out myself.

Matt

 

[Grey_04]

if your area has one of those roadside speed alert signs at a construction area or anywhere.. do a drive by and see what it reads from that..

 

[Grey_04]

oh something else i was thinking about .. has anyone had the dash apart to install a set of those white gauge face kits ? it's possible the needle got bumped or moved.

 

[66sprint6]

Nah, the gauges look like they are stock. It was owned by an older Pilot apparently before my buddy and my buddy had it about a month before I got it from him last night. It appears to be stock as it gets other than spray in liner and a bed cover. It will zero out when you come to a stop and it moves smoothly as you go thru the gears but it just reads way too high.
Matt

 

[Grey_04]

I'd jack the truck up by the rear axle and take the rear wheel and spin it 2 full turns and count the number of times the drive shaft spins. if I'm remembering correctly i read on here that 2 turns of the wheel/3.75 turns of the shaft = 3:73 and 2 turns of the wheel/4.25 of the shaft is 4:10. maybe someone can chime in on that for sure but that would give you a better idea on what's in side if the tag is missing or guts replaced.

 

[66sprint6]

The tag is there and it checks out with the door tag as well but I dont know for sure what the rear gear is. Ill check it out tonight, might just have to pull the cover off and count the teeth...wouldnt hurt to put some fresh fluid in anyways. Thanks for the info on the rear gear, we'll see what it comes out to.
Matt