built shep 5sp only goes 98-97 @ 7k in 4th?
Oct 4, 2008, 09:27 AM
#1
built shep 5sp only goes 98-97 @ 7k in 4th?
Alright the car orginally had a practically brand new Evo 9 5 speed trans in it. When we had the car rebuilt we had the trans rebuilt by shep. Well I've now noticed that the car will only do 97-98mph @ 7k in 4th gear. We've tested this against a GPS. And to make sure the GPS was accurate, we firsted tested it against a stock tranny 05 Evo 8. My friend did about 115 in 4th gear according to his speedo and the GPS.
I talked to shep friday and he told me that its physically impossible that I was only doing 97-98 mph, but according to all the tests I've done, that is in fact how fast the car is going @ redline.
He even factored in my tires, 255/35/18.
Shep said my tach could be off, but we also tested 3rd gear which @ redline the GPS/speedometer read 78-79mph, which was the same mph my friends 05 Evo 8 read.
So something is obviously wrong here. The shorter gearing is absolutely killing my car.
Any ideas?
I talked to shep friday and he told me that its physically impossible that I was only doing 97-98 mph, but according to all the tests I've done, that is in fact how fast the car is going @ redline.
He even factored in my tires, 255/35/18.
Shep said my tach could be off, but we also tested 3rd gear which @ redline the GPS/speedometer read 78-79mph, which was the same mph my friends 05 Evo 8 read.
So something is obviously wrong here. The shorter gearing is absolutely killing my car.
Any ideas?
Oct 4, 2008, 10:14 AM
#4
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Your Math Is Incorrect
You know the stock advans have a 25.3 Overal Diameter right...
if the 255 35 18 has a smaller diameter its means overall the stock tire should make a full rotation slower meaning its going to read slower with a stock tire than with a tire that will spin faster.
Technically if you are running the tire you say you are.. depending on manufacturer, it is possible you are very close to stock but it is not anywhere close to 5% difference.
And.. if his tires were the ones causing the problem. The GPS and the Tach reading would be off.. not the same as he states.
Oct 4, 2008, 10:35 AM
#5
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I'm just going to throw this out there but it looks similar to the rs gear set.
https://www.evolutionm.net/forums/sh...rs+final+drive
Take a look, but it seems like the tach might still have issues. Where does your limiter kick in? You might be able to check that I suppose and compare it to how far off it is?
https://www.evolutionm.net/forums/sh...rs+final+drive
Take a look, but it seems like the tach might still have issues. Where does your limiter kick in? You might be able to check that I suppose and compare it to how far off it is?
Oct 4, 2008, 10:47 AM
#6
Yep I called him first actually before I called Shep. He thought that was odd. Said the only thing that would throw my speedometer off is the tire/wheel combo but I know it should only be off by a couple mph..not 12-13 mph.
Interesting, I'll check into that today. Thanks.
I'm just going to throw this out there but it looks similar to the rs gear set.
https://www.evolutionm.net/forums/sh...rs+final+drive
Take a look, but it seems like the tach might still have issues. Where does your limiter kick in? You might be able to check that I suppose and compare it to how far off it is?
https://www.evolutionm.net/forums/sh...rs+final+drive
Take a look, but it seems like the tach might still have issues. Where does your limiter kick in? You might be able to check that I suppose and compare it to how far off it is?
Last edited by damstr; Oct 4, 2008 at 10:50 AM.
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Oct 4, 2008, 12:33 PM
#9
Evolved Member
Oct 4, 2008, 03:21 PM
#12
I didn't do any math, so I don't have a clue what you're referring to.
I posted two separate things - one comparing road speeds of the VIII and IX transmissions with the size tires the OP says he is using, and one saying that a 5% error (what the OP's car is "off" what he thinks it should be) is WNL even for a GPS. I have a $1000 GPS based data logger that is often 5-10mph off actual car speed. It's all in the calibration of the unit . . .
Those were 2 different ideas. Another one was the slipping clutch idea that was recently brought up, but I doubt that is the case cruizing at no load at redline. If it slipped there, it would slip noticeably at peak torque and the OP would mentioned it.
I don't think so. . . isn't the tach signal generated from a sensor in the trans? If that's the case, you could put a 12" diameter tire on the car and at 7K rpm in 4th gear the speedo will read the same as it will with the stock tires.
Where you are getting confused is that at a set rpm, ANY tire you put on the car will rotate at the same rate. Bigger tires just cover more ground with each revolution. . .
I posted two separate things - one comparing road speeds of the VIII and IX transmissions with the size tires the OP says he is using, and one saying that a 5% error (what the OP's car is "off" what he thinks it should be) is WNL even for a GPS. I have a $1000 GPS based data logger that is often 5-10mph off actual car speed. It's all in the calibration of the unit . . .
Those were 2 different ideas. Another one was the slipping clutch idea that was recently brought up, but I doubt that is the case cruizing at no load at redline. If it slipped there, it would slip noticeably at peak torque and the OP would mentioned it.
Where you are getting confused is that at a set rpm, ANY tire you put on the car will rotate at the same rate. Bigger tires just cover more ground with each revolution. . .
Last edited by EVOlutionary; Oct 4, 2008 at 03:37 PM.
Oct 4, 2008, 03:34 PM
#13
I didn't do any math, so I don't have a clue what you're referring to.
I posted two separate things - one comparing road speeds of the VIII and IX transmissions with the size tires the OP says he is using, and one saying that a 5% error (what the OP's car is "off" what he thinks it should be) is WNL even for a GPS. I have a $1000 GPS based data logger that is often 5-10mph off actual car speed.
Those were 2 different ideas. Another one was the slipping clutch idea that was recently brought up, but I doubt that is the case cruizing at no load at redline. If it slipped there, it would slip noticeably at peak torque and the OP would mentioned it.
I posted two separate things - one comparing road speeds of the VIII and IX transmissions with the size tires the OP says he is using, and one saying that a 5% error (what the OP's car is "off" what he thinks it should be) is WNL even for a GPS. I have a $1000 GPS based data logger that is often 5-10mph off actual car speed.
Those were 2 different ideas. Another one was the slipping clutch idea that was recently brought up, but I doubt that is the case cruizing at no load at redline. If it slipped there, it would slip noticeably at peak torque and the OP would mentioned it.
As for the clutch, no its definitely not slipping. I did a first to second gear pull yesterday and lost traction when banging second. lol
When I did the testing I helt it at redline for less then 5 seconds, just enough to where the mph on the GPS would be steady.
Last night we were going down a road, he was right next to me, we both were in 4th gear going 40mph, his tach read 2500rpms, mine read approximately 2750. So right there I'm obviously a little off.
Oct 4, 2008, 07:12 PM
#15
What you just posted confirms the difference is just the normal differernce between the 4th gear ratios of the 2 cars. . . .
40mph in a VIII with 25" tire should be 2500rpm
40mph in a IX with 25" tire should be 2700rpm
If your friend has the stock tires the difference will be even greater. . .
EVOlutionary