Floorman279

iTrader: (11)

hey guys, i put an s60 with 373s in my 98 z28 m6 car, and got the speedo recalibrated along with a tune.......the guy i took it to has done quite a few recalibrations, and i trust he did it right, but my speedo still seems like its reading too low.....i wrote down some speeds in different gears and what the rpms were, and was wondering if you guys with 373s could maybe check one or two of these if you remember while driving your cars....

1st @ 4000............28 mph
2nd @ 2000...........20 mph
2nd @ 4000...........42 mph
3rd @ 2000...........28 mph
3rd @ 3500............49 mph
4th @ 2500...........46 mph
4th @ 3500............64 mph
5th @ 3000...........74 mph
6th @ 1500...........50 mph
6th @ 2000...........69 mph
6th @ 2300...........82 mph

i no i went a boit excessive, but was bored....i know that it wont be perfect, and i know that the speedo is naturrally probly goona be off by 1-2 mph, but seems more than that off.......i remember that before the swap, 6th gear @ 2000 rpms with 342s was 81-82 mph, so the fact that its now 2000 at 69 mph, 12-13 mph less seems like a big jump......i know a lot of you guys use that fbody.org thing for your gear ration calculator, and that shows a 7mph difference in 6th gear @ 2000......again if i was maybe 9 or 10 off, i wouldnt be too worried, but am i wrong for thinking something may be off still? thanksguys

Floorman279

iTrader: (11)

and as far as i know, the tranny has all stock ratio gears

FirstYrLS1Z

iTrader: (4)

check the speedometer against a GPS unit,most display MPH.

Floorman279

iTrader: (11)

will try tomarrow, do my numbers seem off tho

01ssreda4

iTrader: (96)

Yep, GPS would be the best way.

Floorman279

iTrader: (11)

gps was pretty close to accurate, but what i cant understand is that my actual speeds are pretty far off from the gear ratio calculators actual speeds said im supposed to get......i measured my tire even, and that got it close but still pretty off......just wondering what you guys actually running 3.73s are getting for each gear.....i mean, 82 mph was 2000 rpms in 6th with the 3.23s, now its 2000 is 69 in6th.......doesnt that seem like a big jump? i mean the calculator says i should be at 79 at 2000 rpms......just very confused is all

speed_demon24

iTrader: (6)

Tach could be off.

And check out
www.f-body.org/gears

Floorman279

iTrader: (11)

fbody gears id what i was using and im way off from those numbers......how do i check that the tach is accurate

BlackLS1Bird

iTrader: (2)

I got a rather large speeding ticket in mine not too long ago. Took it to a speedometer calibration checking shop where they put it on a dyno-looking machine and run it through the gears and they write down the difference between speedometer reading and actual speed. Can take that back to the tuner if it is off and get it readjusted. BTW, when my speedo reads 45 the car is actually doing 105. I would love to only be about 10 off. lol. Need mine retuned for the 6 speed swap.

BlackLS1Bird

iTrader: (2)

Where are you located FLOORMAN?

Predator

My speedo was off because I just accepted the 25.66" formula for my tire and wheel combination. I got my tape measure and it turned out that my tires and wheels were actually 25 inches.

Floorman279

iTrader: (11)

ill look into that