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**mike malloy** · 01-26-2002, 04:28 PM

i have the y87 option. i'll post numbers tommorow ;) ;) ;)

**MustangEater8251** · 01-26-2002, 05:33 PM

aren't rim\tire size a factor too?

**Damien214** · 01-26-2002, 05:48 PM

No, I just want to know what it runs with stock tires and rims. Mine are the equivalant. and so are Strobhens. if you have 16's with 55 profile or 17's with 40 profile you are my person.

**V6Bob** · 01-26-2002, 06:06 PM

My 5 speed Y87 goes a little less than 30mph/1000rpm. That means your 3.73 should go

3.08/3.73 X 30 = 24.5mph per 1000 rpm,

just about what you're seeing.

3.42 gears would go

3.08/3.42 X 30 = 27 mph per 1000rpm

or about 2750 at 75 mph.

The guy who says he's turning 2300 at 75 with 3.42 gears has a wonky speedo or tach. There is no "magic transmission" stuff going on.

Tire size doesn't matter, as long as we're talking speedo readings.

[ January 26, 2002: Message edited by: V6Bob ]

**Damien214** · 01-26-2002, 06:21 PM

Would a different ratio 4th gear be considered a "magic transmission"? [img]tongue.gif[/img]

**wheeldog63** · 01-26-2002, 06:31 PM

Correct me if I am wrong, but....don't you have to use something to compensate for the change in the gears, like a speedo-fix thing? I have head people talking about having differant gears and having their speedo off? Just a suggestion.

**Damien214** · 01-26-2002, 06:44 PM

That affects mph readings, I'm talking about rpm's which is unaffected by gear changes. And V6Bob, your thinking is flawed, because according to your calculations that would put your top speed into 180 mph, and what about HP? a 500 hp car will go faster than a 200 hp car with the same gears, so there is more at work here than simple equations like this. Hypertech has put the top speed of your car at 145 mph not given wind resistance of course. By that you could say that if he goes 145 mph at 6000 rpm then he will have right about 24 mph per 1000 rpm. Which would mean that his 3.23 geared M5 goes 75 at 3000 rpm.

And there is a difference between autos and M5's, I only want auto rpms.

**Wolfy** · 01-26-2002, 07:47 PM

I have a 97 A4 Y87 and when I finally break 2500rpms is at about78 mph, i breack 3000rpm at exactly 90mph, so those #'s sound about right to me

**Rik** · 01-26-2002, 08:01 PM

My 99 A4 Bird didn't start out as Y87, but it is now. I had 3:42's and a posi put in at Allen's Gearworks in Tampa. The speedo was off by about 10%, until I had the ECM reprogrammed at Courtesy Pontiac in Orlando, using the VIN from a 2000 model Y87 car.
Tonight on the way to a restaurant with my wife, I paid attention to the tach...at 35, I'm doing 1500 rpm's...it shifts up into fourth around 45-50 mph, so I'm STILL doing 1500 at 55. There was too much traffic for me to check 75 mph during the short drive, but next time I get the chance I will let you know.

Rik

**Infernal** · 01-26-2002, 10:13 PM

I dont have Y87 but my car did come with GU6 and G80 and when my speedo is set on 75 MPH in 4th gear the tach reads 2250.

[ January 26, 2002: Message edited by: Infernal ]

**DominusEtDeusNatus** · 01-26-2002, 10:24 PM

<blockquote>quote:<hr>Originally posted by 10SecDream:
I need help guys, because I have done a rear end swap to 3.73 gears and now I am at almost 3000 rpm when at 75 mph. Tom who has a y87 with 3.42 gears says his car is about 2200-2300 at 75 mph. If you all have similar numbers that means the y87 and the 3.08 open have the same freeway mph and thus same top speed with improved acceleration. What I'm trying to currently figure out is WHY! and HOW!

I contacted Magnus who has put in a Y87 PCM after a gears swap from 3.08 to see what his results were. If his car in fact does the same as yours it may be possible to electronically control the engines rpms. If he doesn't have the same results that you guys do then perhaps we are dealing with either
A: A different version of the 4l60e that has a compensated 4th gear or
B: GM has put something somewhere on the car that controls the engines RPM's when driving. I think if i'm correct this could be a major break through in tuning these cars for top speed and acceleration.

Here is what I need from you guys, if you have a GU6 code and dual exhaust on a 3.8 then congrats you have y87. This means I need YOUR help.

Post here with 4 numbers

Engine idle:
35 MPH RPM's
55 MPH RPM's
75 MPH RPM's

We are gonna beat GM at their own game if it kills us. Please help guys. [img]graemlins/penguin.gif[/img] <hr></blockquote>

I'm really lost as to what you are trying to do. As mentioned, there is no magical stuff going on here. Top speed is also drag limited. You don't have enough horsepower to go as fast as a V8. Someone's tach is off and it's as simple as that. There is no way that guy was going 2300 at 75 with 3.42 gears. I had 3.42s and didn't go no 2300 at 75.

Aren't you the same guy that though you could change the gear ratio inside the transmission?

**Riles** · 01-26-2002, 10:35 PM

<blockquote>quote:<hr>Originally posted by 10SecDream:
That affects mph readings, I'm talking about rpm's which is unaffected by gear changes.
<hr></blockquote>

Actually, you *were* talking about the speedo. You wanted to know how many mph people were going at a given rpm. Thats what needs to be corrected if you do a gear swap.

If your at 3000 going 30 (numbers picked out of a hat), and you change your gears, your speedo will still think you are going 30 at 3000 rpms, whereas you will actually be going faster or slower, depending on the gears you changed to.

So, if somebody had a speedo that needed re-calibration, it would throw off your whole "theory", as their speedo would read false speeds at any given rpm.

**shortdog273** · 01-26-2002, 10:44 PM

I was reading the mod. encyclopedia and it stated that your rpms are higher with a 3.73 gear. My rpms are at about 2200 between 70-80mph. Dom, maybe you're right about the meter reading being wrong, but how can you be so sure?? Me, Wolfy and a few others are showing the same readings on a 3.42 gear.

[ January 27, 2002: Message edited by: shortdog273 ]

**strobhen** · 01-27-2002, 12:05 AM

I have 3.42 gears and y87

I just went out on the highway tonight

75 mph, looked like about 2250 rpms. Definitely way under 2500. With the analog nature of the needle, I would say 2350 at the *absolute* most assuming it is not completely screwed up, which I doubt.

I have no mods that would make any difference in the readings of rpms & mph. Stock tires, gears, etc.

So Dom, I'm afraid you are wrong.

And yes Dom, he was the one that was looking into that because of his terrible gas mileage. You technically can change the gear ratios, just nobody does it. I mean what, do you think GM couldn't put different ratio gears in there if they wanted to? [img]tongue.gif[/img] He did find an overdrive device though, good device except he couldn't put torque arms or a driveshaft safety loop on there, and for what he is trying to do, both are necessary.

Got it done a couple days early Damien, there is your answer, looks like I remembered my trip from TN pretty well (it was, btw, about 2000-2250 going 70-75 the whole way down from TN to Central FL)

Later

Edit: Btw, to anyone who says it runs higher than 2250, how do you know *your* tachometer isn't off? Hmmmm?

[ January 27, 2002: Message edited by: strobhen ]

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