Theoretical gear question (lets get some real tech in here)

[Pokageek]

So the next question is, what speed does the car top out at in 5th gear with the 3.73, 4.10, 4.30? I am curious..why does fifth have to be considered poop?

I would also like to know what gear my 3.55's top speed is and how fast that is? Good Q&A here.

 

[4Jenna]

C'mon man u know there is no tech in the 94-95 room...hasnt been in years

 

[ninjacoupe]

So the next question is, what speed does the car top out at in 5th gear with the 3.73, 4.10, 4.30? I am curious..why does fifth have to be considered poop?

I would also like to know what gear my 3.55's top speed is and how fast that is? Good Q&A here.

Tire Diameter in inches multiplied by RPM multiplied by .002975 then divide it by your rear gear ratin and that will be mph in fourth.

26 tire X 5000 rpm X .002975 =386.75

386.75 divided by 3.55 gears =108.9 mph now if your fifth gear ratio is stock 90-93 t5 its .68

Divide MPH in fourth by .68

108.9/.68=160mph<-------Assuming you had the HP to pull it off. Its a mechanical theoretical limit.

 

[GRGT1994]

I'll offer my real world experience on higher (numerically) gears for highway WOT and rolling downshift squirts. My 4.10's are pretty fun out there. But it does not take long and I am literally running out of gear. Not too far before I'm toping out 4th gear. And shifting into 5th from a redlined 4th gear is not fun. The synchros for 5th are not designed for WOT speedy shifts. So I have to let the engine drop way down.

All that said, I guess I was thinking that something like 3.55's might be better suited for what you are looking for. IMHO.

 

[Killercanary]

Mike, I'm not entirely sure what you are asking exactly, but maybe this is will help.

I'm going to use an extreme example in this case for illustration purposes... a supra. Look at this dyno graph:

At the track...
As you can see if this car was setup was setup with a rear gear ratio that had it crossing the finish line at or before 5000 he would have been leaving a TON of trap speed and ET on the table. A gear swap in this situation could be worth a TON of MPH and ET. The same holds true for our cars... if you cross the line before your peak your not running as good as you can be. I made the switch from 3.73's to 4.10's for this purpose. My car makes peak power at 5500 but it is still carrying very well out to 6000 where I shift. The 4.10's have me crossing at right around 5900 with my 26" high tires which is damn near perfect for my combo. Here's my dyno graph..

On the street...
If the above mentioned supra were to "roll race" and a drop from 4th to 3rd dropped the rpm to 4000 the opposing car would have a lot better of a chance than if the supra was at a high enough speed in 4th that the resulting RPM after downshifting to 3rd would have it at 5500 or better. Ideally in a turbo car like the supra you'd like to have a gear ratio that willl have the car in the appropiate rpm range but also one that loads the car more than a higher gear ratio as load creates exhaust heat which in turn spins the turbine. In a mustang the same holds true. If you want to roll race the car, then you should try and figure out at what top speed you think you'll stop racing. If its 120, then select a gear that will pull 4th and have you at 120mph just slightly above your peak rwhp RPM. Does that make sense?


P.S.- I started typing this reply yesterday and got sidetracked, so some of the stuff may have already been covered above.

 

[Grn92LX]

I follow what you're saying Paul. I got my answer already. Basically with these 3.73's i'm not able to use all of my powerband in 4th gear so that will hurt me on the street from a punch just as it is on the track. I think im gonna ask santa for fms 4.30's for xmas

Like I've said in this thread, my car makes power higher, spins higher and I have a PMS to raise the limiter to what I want. I will not be running out of gear. if I had a stock limiter and my old 6000 rpm 302, then yeah i'd run out of gear. My limiter is 6,800 now and can be changed higher if need be. This cam should have useable power to 6700 ish.

 

[94Blue302GT]

I'm putting in a TKO and 3.73's. The TKO has a bit steeper first, but a lower 5th. I will have no problem ripping any of the gears up, I gots turbo power.... well, soon...

 

[OrangeMustangGt]

Ok, here is a guestion, On a turbo car, where is the sweetspot, gearing wise between gearing high for load on the engine to spool the turbos, and gearing low for better acceleration? For example, my car actually pulls just as hard in 2nd than 1st for this reason, i have 3:73's, but would dropping to say 3:55's help or hurt, see what im saying?

 

[94Blue302GT]

Ok, here is a guestion, On a turbo car, where is the sweetspot, gearing wise between gearing high for load on the engine to spool the turbos, and gearing low for better acceleration? For example, my car actually pulls just as hard in 2nd than 1st for this reason, i have 3:73's, but would dropping to say 3:55's help or hurt, see what im saying?

With a stock ratio'd T5 a 3.55 or 3.27 would be better, maybe even 2.73 if you've got a really nice setup.

I'm keeping the 3.73's because with a .96 A/R it'll take a bit more to spool, and the gear will make it easier to get to that point. Plus, since it's on the street, it'll be easier to throw around corners and drop a gear or two to catch the next car. If it were a total drag car, i've got a set of 3.27's to put in.

 

[Grn92LX]

I'm putting in a TKO and 3.73's. The TKO has a bit steeper first, but a lower 5th. I will have no problem ripping any of the gears up, I gots turbo power.... well, soon...

A tko has a 3.27 first, a T5 is 3.35. 5th for both is .68.

 

[94Blue302GT]

I thought there was an option for the different gears on 5th for a TKO?

 

[nmcgrawj]

I thought there was an option for the different gears on 5th for a TKO?

I think it depends on which model you are talking about, im almost positive the new ones are a .64 5th gear....where as the g-force is a .59.

 

[1slow95]

Ok, here is a guestion, On a turbo car, where is the sweetspot, gearing wise between gearing high for load on the engine to spool the turbos, and gearing low for better acceleration? For example, my car actually pulls just as hard in 2nd than 1st for this reason, i have 3:73's, but would dropping to say 3:55's help or hurt, see what im saying?

I have kind of a similar problem, I can tell mine pulls harder in first when it hooks, but then I have to shift after about a second or two. If I can get something in between 1st and 2nd, I think that would really help the car, at least in the fun factor.

You can kinda see what I mean in this vid, this is 2nd gear. Video

 

[nmcgrawj]

I got another question for you guys...u know when people say a specific car has a strong 3rd gear or 2nd gear or whatever the case is, i can understand when its a turbo car how or why that can happen.

But in a n/a car, how does the gear, which actually is the load, change to make the car faster? It seems like if anything, its the gearing in the transmission and not the engine producing the effect so people think its faster. But, well, i dunno...maybe someone gets what im trying to ask.

 

[mytight95]

Green....i would think that the 4.30's would help get on down the road faster....even though you have to shift more(less time in each gear) you pull in top gear will be harder and faster accelleration wise...... IMO...\



jason

 

[maximos]

My roommate has 3.73's in his 93 Cobra, I have 3.27's in my 95 Cobra...We raced on the highway and he pulled ahead a little bit immediately, my gears are longer so I would gain on him at the top of each gear. Hope it helps...

 

[nmcgrawj]

My roommate has 3.73's in his 93 Cobra, I have 3.27's in my 95 Cobra...We raced on the highway and he pulled ahead a little bit immediately, my gears are longer so I would gain on him at the top of each gear. Hope it helps...

That confuses me...with the same engine...wouldnt the 3.73's be better? So he should get the jump since the 3.73's accelerate him faster, but unless he is shifting slow or something, or his rpm's drop down outside of his power band, i dont see where u would get the window to catch up. Cause once u are running...u are constantly in the power band right?

 

[Grn92LX]

That confuses me...with the same engine...wouldnt the 3.73's be better? So he should get the jump since the 3.73's accelerate him faster, but unless he is shifting slow or something, or his rpm's drop down outside of his power band, i dont see where u would get the window to catch up. Cause once u are running...u are constantly in the power band right?

Whats happening in this case is the 373 geared car shifts sooner and the rev's will obviously drop down while for a split second the 327 geared car is still up top in its rpm band so with the sooner shift the 327 geared car will start to kinda gain on him until he has to shift, then he drops down and his rev's pull slower so the 373 geared car will pull more.

 

[maximos]

That confuses me...with the same engine...wouldnt the 3.73's be better? So he should get the jump since the 3.73's accelerate him faster, but unless he is shifting slow or something, or his rpm's drop down outside of his power band, i dont see where u would get the window to catch up. Cause once u are running...u are constantly in the power band right?

My gears are longer, so if he is in third gear then shifts to fourth, i'm still in third gear in high rpms accelerating faster than him at that moment. but eventually i have to shift as well giving him another opportunity to pull away

 

[Zero Signal]

The longer you can stay in the lower gear, the faster you will be, period. That's why they say not to get a steep gear unless you have a really high shift point. It comes back to the indy car vs semi truck thing. If you have a nice flat torque curve, use it with a lower gear. It's what makes the new GT40 so fast. But then you have an indy car with less than 300 ft-lbs of torque that will blow it away becuase it's power band is so damn high and they can use a crazy steep gear to take advantage of it.