Speedometer error
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Speedometer error
Hi All
I am looking at troubleshooting my speed error. I just bought a 1991 F350 7.3 (with a Banks aftermarket turbo) with a 5 speed manual transmission. Coming home yesterday I noticed traveling at 110 k/h (65 m/h) that my tach was reading just over 2. My other truck ran at about 2250 running the same speed, mind you I had the E40D Auto. I increased up to 122 k/h (75 m/h) just to get to the same RPMs. I checked the tire size and they are correct. I am wondering if the speed can show an error as it the gears in the housing wears (gear for the speed cable).
I am looking at troubleshooting my speed error. I just bought a 1991 F350 7.3 (with a Banks aftermarket turbo) with a 5 speed manual transmission. Coming home yesterday I noticed traveling at 110 k/h (65 m/h) that my tach was reading just over 2. My other truck ran at about 2250 running the same speed, mind you I had the E40D Auto. I increased up to 122 k/h (75 m/h) just to get to the same RPMs. I checked the tire size and they are correct. I am wondering if the speed can show an error as it the gears in the housing wears (gear for the speed cable).
Posting Guru
Joined: May 2003
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From: Joliet, Illinois
ONCE AGAIN I POST!
You have to take into account your axle ratio and high gear ratio of your trans as some have had differing ratios.
My E4OD with .71:1 high gear and an axle ratio of 3.55:1 with the converter locked up i get about 2000 rpm's at 65 mph.
At those rpm's I would have a 3.99:1 axle ratio with my E4OD.
What are your ratios and how tall is your tire?
And as for wear, when it is worn that bad, they dont loose a couple of mph, they lose it all together.
You have to take into account your axle ratio and high gear ratio of your trans as some have had differing ratios.
My E4OD with .71:1 high gear and an axle ratio of 3.55:1 with the converter locked up i get about 2000 rpm's at 65 mph.
At those rpm's I would have a 3.99:1 axle ratio with my E4OD.
What are your ratios and how tall is your tire?
And as for wear, when it is worn that bad, they dont loose a couple of mph, they lose it all together.
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As I stated, I just bought the truck and I am in the middle of troubleshooting the speedo error. The plate on the door and the tire size is the same so that rules out the tires. I have no idea if one of the other owners has done any thing with the rear end. I just wanted to knock off easy fixes first. I am thinking that the rear end gears may have been changed and this is the cause.
Posting Guru
Joined: May 2003
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From: Joliet, Illinois
Well if the trans ratio is not the same and the rear end is not the same, you can not compare the two vehicles as YOU CAN NOT ASSUME THERE IS AN ERROR WITHOUT VERIFYING THE RATIOS!
That truck could have come with any number of rear axle ratios and the ZF 5 speed i believe also came with different ratios, so assuming they all will cruise at the same rpm at the same speed is nuts!
THERE IS NO SPEEDO ERROR!
How is that for an easy fix?
That truck could have come with any number of rear axle ratios and the ZF 5 speed i believe also came with different ratios, so assuming they all will cruise at the same rpm at the same speed is nuts!
THERE IS NO SPEEDO ERROR!
How is that for an easy fix?
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You idiots are no help. What I was trying to do BEFORE looking at the rear end (pulling the cover off etc) was to see IF there were other issues that others may have seen with the speed errors.
Since you only want to pick apart my statements then #$%^ it!
Since you only want to pick apart my statements then #$%^ it!
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And just to shut you chaps up. I ran my truck side by side with my SUV running at 100 k/h and on my speedometer it was reading 115! A diference of 15%
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Posting Guru
Joined: May 2003
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From: Joliet, Illinois
Originally Posted by Scouterstan
And just to shut you chaps up. I ran my truck side by side with my SUV running at 100 k/h and on my speedometer it was reading 115! A diference of 15%
We are here to help, but when someone supplies incomplete info, it can make them seem like they do not know what they are talking about.
You should have started with the 15% info and we could have gone from there.
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Beg, borrow or even BUY a GPS reciever, they all have a very acurate speedometer.
That you you can be sure of your road speed, rev counter error, rolling radius of tires and different axle ratio than you are used to may be what you are looking at.
Please be polite on this board even if you are ticked off, there are a lot of helpfull people on here thet I for one am deeply endebited to for their friendly help, advise and information.
Steve
That you you can be sure of your road speed, rev counter error, rolling radius of tires and different axle ratio than you are used to may be what you are looking at.
Please be polite on this board even if you are ticked off, there are a lot of helpfull people on here thet I for one am deeply endebited to for their friendly help, advise and information.
Steve
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Joined: Apr 2005
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From: NC
Originally Posted by Scouterstan
And just to shut you chaps up. I ran my truck side by side with my SUV running at 100 k/h and on my speedometer it was reading 115! A diference of 15%
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From: Nutter Fort, WV
235/85-16 tires with 3.55 gears behind a ZF 5 will run 78 MPH at 2250 RPM.
235/85-16 tires with 4.10 gears behind a ZF 5 will run 65 MPH at 2150 RPM.
235/85-16 tires with 4.56 gears behind an E4OD will run 65.5 MPH at 2250 RPM.
235/85-16 tires with 4.10 gears behind a ZF 5 will run 65 MPH at 2150 RPM.
235/85-16 tires with 4.56 gears behind an E4OD will run 65.5 MPH at 2250 RPM.
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Originally Posted by Dave Sponaugle
235/85-16 tires with 3.55 gears behind a ZF 5 will run 78 MPH at 2250 RPM.
235/85-16 tires with 4.10 gears behind a ZF 5 will run 65 MPH at 2150 RPM.
235/85-16 tires with 4.56 gears behind an E4OD will run 65.5 MPH at 2250 RPM.
235/85-16 tires with 4.10 gears behind a ZF 5 will run 65 MPH at 2150 RPM.
235/85-16 tires with 4.56 gears behind an E4OD will run 65.5 MPH at 2250 RPM.
