Hello everyone.

The other day I had some 3.73 Gears installed in my car. I drove it for 2 or 3 days & now today I took it out to the track. I ran several times... the best I could get was a 13.7 and most runs were in the 13.9 or 14.0 range... I am certain I was running these 13.9 or 14.0 range when I was stock... and the car seems to FEEL faster than before the 3.73s

I have an Intake, 3.73 Gears, and of course a Tune. Before the gears were in I ran a best of a 13.453 which I lost the time slip for... so I will show a different comparison of some runs before and after.

Before:
R/T .565
60' 2.117
330' 5.814
1/8 8.820 @ 81.84 MPH
1000 11.405
1/4 13.586 @ 103.03 MPH

After:
R/T .094
60' 2.127
330' 5.824
1/8 8.872 @ 80.81 MPH
1000 11.497
1/4 13.734 @ 100.56 MPH

I have come up with a few possibilities of what might have gone wrong...
1) Track timing/clocking equipment was messed up or really bad track conditions (a couple people were saying they were running slower... others said they didn't notice anything... I saw a couple cars that should have ran faster... gto ran 14.4 and 350z ran a 14). This may be most likely as last time I went it was reporting a trap speed that couldn't have been right... like 80 mph
2) Wrong tune was installed by shop. If so I re-installed it when I got home. (lesson learned to bring tuner to track...)
3) Doug gave me a bad tune?
4) Something not right with gear install


Opinions?

could be any of the above. i was told about .3 to .4 off 1/4 times. i would reload the tune and try again

Yeah I reloaded the tune and I am going to go back on Friday and see what happens... also going to try contacting Doug & have him check out the tune.

Did you have your shift points changed for the 3.73's ?????

I think that's the problem.

I ordered a new tune from Doug and put on there that I had 3.73 gears and JLTII Intake... would he have done the shift points already?

If not what do I need to do?

ORIGINAL: Bluestar

Did you have your shift points changed for the 3.73's ?????

I think that's the problem.


That is a good call, I didn't notice he had an auto.

Your trap speeds dropped significantly too, I'm thinking a badDA might have had something to do with it too

What are the shift points with 3.73s suppose to be?

What was the weather like on the different days? Higher temps and humidity can have a pretty big impact on track times.

ORIGINAL: SilvrStang

What are the shift points with 3.73s suppose to be?


they would need o be adjusted due the gear ratio change. i believe that the rpm points would remain the same - the computur would have to be told that the gears were changed

Could be weather and track conditions. Seems to me maybe you were spinning off the line more.

it could that u need to brake in those gears a little bit more, 2-3 days not enough

Maybe... but I was rading & seems there was a lot of disagreement on that subject. These things are quiet... can't hear them at all.

I don't think it was the weather because I was running these times when I was stock, in 90 degree weather and it was only 70s today.

I'm thinking a worse DA. Make sure your tune is correct and go again and see what happens.

I calculated DA and it was around 2500... the track is at 800 feet but weather would have made the DA higher. But, that still doesn't explain such a large difference..

im no expert but dont u need 500 miles to break in the gears ???

^ thats what is recommended. Yea 2-3 days uh... your gonna be hearing some noise in a while.

Like others have said the weather and track conditions play a huge part in ETs.

Hmm well thanks for the advice... maybe ill take it easy then.

Well think I figured out the problem.

Seems to be a bad tune. I tried flashing back to the tune I had before the gears and now I am running back around 13.5 . Did a few back to back runs and each time the old tune ran better. I did go into my tuner when flashing the car and selected 3.73 ratio.

I am at the track now so far best 13.465.

Get some stickies, shift kitand a stall and you can maybe dip into 12s

did you track give you any issues running under 13.5 with a vert without a cage? Where is your track located?

Nope they did not give me any issues. KCIR its in Kansas City Missouri.

I might get stickies... but don't think I am going to get a stall due to the fact this is my DD and only car ;P

ORIGINAL: gburke1

Well think I figured out the problem.

Seems to be a bad tune. I tried flashing back to the tune I had before the gears and now I am running back around 13.5 . Did a few back to back runs and each time the old tune ran better. I did go into my tuner when flashing the car and selected 3.73 ratio.

I am at the track now so far best 13.465.


those are great times with only an intake/tune and gears.:D

Just out of curiosity,how much faster does it feel with the new gears and proper tune now??

Well I don't really think it's that great because I ran a 13.453 @ 103.89 before the gears :P . The tune actually still is not the proper tune... waiting on Doug to send me a revised one. I am just running the tune I had before I installed the gears, but went in with my Xcal2 and manually changed the gear ratio.

It doesn't really feel much different right now unfortunately ;( , maybe when I get the new tune I will notice.

I also found out from a friend who had my car up on a lift that apparently I have an aftermarket H-Pipe I didn't even know about O.o . Must have been there when I bought the car... hopefully they didn't have 4.10s on there too! lol that would explain everything... Unfortunately don't know how to figure out what H-Pipe it is, and my friend could not tell.

thats what i was thinking, maybe you had 4.10's in before and dident notice?

idk.

good luck

Do you remember what rpm ur at and what gear in ur in before and after the install at the track. If ur rpm has dropped after the install, that would make me believe you did have the 4.10s but if your trapping at a higher rpm then before; ur gold.

being that stock auto have like 3:31 gears, a set of 3.73 should help a lot!

O and btw a stock geared gt should be in third gear before going through the trap, at least my stock gt w/ 3.55 gears is. I'm also looking into 4.10s or 3.73s.

if they were 4.10s that might explain why it 'feels' faster with the 3.73s.
(with better traction off the line)

If you were just spinning the wheels at launch(4.10s) it might explain the quick times
and higher trap speed.

I know it's apples to oranges but with my old srt-4 stage 2 if I launched it conservatively I would get a better time though a low trap speed..but if I fried the tires off the line I would trap 1-2 mph higher though my trap was a little slower.

ORIGINAL: gburke1

Hello everyone.

The other day I had some 3.73 Gears installed in my car. I drove it for 2 or 3 days & now today I took it out to the track. I ran several times... the best I could get was a 13.7 and most runs were in the 13.9 or 14.0 range... I am certain I was running these 13.9 or 14.0 range when I was stock... and the car seems to FEEL faster than before the 3.73s

I have an Intake, 3.73 Gears, and of course a Tune. Before the gears were in I ran a best of a 13.453 which I lost the time slip for... so I will show a different comparison of some runs before and after.

Before:
R/T .565
60' 2.117
330' 5.814
1/8 8.820 @ 81.84 MPH
1000 11.405
1/4 13.586 @ 103.03 MPH

After:
R/T .094
60' 2.127
330' 5.824
1/8 8.872 @ 80.81 MPH
1000 11.497
1/4 13.734 @ 100.56 MPH

I have come up with a few possibilities of what might have gone wrong...
1) Track timing/clocking equipment was messed up or really bad track conditions (a couple people were saying they were running slower... others said they didn't notice anything... I saw a couple cars that should have ran faster... gto ran 14.4 and 350z ran a 14). This may be most likely as last time I went it was reporting a trap speed that couldn't have been right... like 80 mph
2) Wrong tune was installed by shop. If so I re-installed it when I got home. (lesson learned to bring tuner to track...)
3) Doug gave me a bad tune?
4) Something not right with gear install


Opinions?




Make sure the shop switched the gear ratio on the car's computer otherwise the speedometer says your going faster than you are, and if so you may be shifting when not in true powerband and slowing down?? Just a thought if no one has already said that?

my 01 had 3.73 and I wish I never made that mod. I ran the same. You gotta scream it thru the traps, that's what I found and the best I ever did was 14.01 in that car with a Hypertech and a cai. It averaged 14.2