Noticeable Difference between 3.55s and 3.73s?

[fiveoho]

That combo wants a 4.10 gear. But a 3.73 will do 'ok'. I'll be doing 4.30's in my little pump gas streeter.

It sounds like you are getting VERY bad advice from your friends/people on the net. You picked great cyl heads for your 306. You could have done a LOT better on the cam/manifold choice though.

The difference between a 373 and a 410 on the highway is about 250 rpm's. They're fine for the highway unless you have a pus sy between your legs

so youre sayin with the 4.10, that should help with the bottem end 'guts' quite abit? and the rest of the combo should be "ok"

 

[Grn92LX]

so youre sayin with the 4.10, that should help with the bottem end 'guts' quite abit? and the rest of the combo should be "ok"

Are you talking abot low end pull? If so, yeah more gear will always help out with that.

I just realized you have a 95. They are heavier than foxes so thats another reason to go 4.10.

Your combo seems ok but I would have done a better manifold and cam.

 

[fiveoho]

Are you talking abot low end pull? If so, yeah more gear will always help out with that.

I just realized you have a 95. They are heavier than foxes so thats another reason to go 4.10.

Your combo seems ok but I would have done a better manifold and cam.

gotcha.

well, like i said. this is my 1st, so it aint gonna be perfect.

i can ask 20 more ppl about a intake / cam.

-10 will say tfs track heat (more rpms) and custom cam (lot more power in custom grind).

-10 will say tfs street heat (more low end grunt) and a shelf tfs 1 or 2 ( not enough difference in custom grind for what im doing)


ive already asked too many ppl about that stuff...im just gonna stop.

 

[mikemustang289]

Choosing an Optimal gear

If you want to know what gears to run you can make the decision based on a few different things.

I went from 3.55 to 3.73, and now I run 4.30's

The biggest factors in determining what gear to run are the transmission ratios and tire size.

I am not familiar with the tremec's ratios but to give you an idea of what I did and what helped me in my decision I used an RPM calculator/ MPH calculator to give me the rpm's I would be at on the highway.

I originally ran a stock T5, 1rt gear was 3.35:1 and 5th gear is 0.68:1. With the 3.73's my final drive ratio in first was (3.35 X 3.73) = 12.5:1, definitely enough gear to get my car up in the rpm quickly. On the Highway in 5th I was looking at (0.68 X 3.73) = 2.55:1

A 2.55 final drive ratio is great for me on a 26 tall tire, at 75mph Im only turning ~2500rpm

Now I'm running 4.30's. Seems like a drastic change right? Well, not really because I changed my Tranny's gear ratio's. I have a 2.95 T5z gear set and I had the trans built with a 0.59:1 5th gear. So if we do the math again, in first I am looking at (2.95 X 4.30) = 12.7:1 still very close to the stock T5 with 3.73's

In 5th (0.59 X 4.30) = 2.54:1. You can see how with my current setup using 4.30 gears I'm still only turning 2500rpm on the highway. The final drive is pretty much the same.

The biggest difference between the two trannies is the 1-2 shift. The stock t5 would drop 41% in RPM from 1rst to 2nd. The 2.95 gearset drops only 33%. The difference is shifting now from 1-2 @6000 puts me at 4020rpm. Before shifting at 6000 would drop me down to 3540 rpm.

In addition to that I also have higher ratios in 2nd, 3rd, and 4th with my final gearing at the track being 4.30:1

That is also important to take into consideration because you'll want to cross the line where the engine makes peak power or close to it.

The switch for me from 3.73's to 4.30's and to the new trans netted me no gain in e.t. The reason for that is my current motor falls flat after 5500 and stops pulling in 4th gear before I cross the line. From that standpoint my gearing selection was wrong but I am currently building another motor which should peak at 6100rpm, one of the reasons I chose the 4.30's and not 4.10's

To explain that the engine I am building should put me in the 12's at close to 105mph. I gave myself room for a bit of error here.

With the 4.30s, at a 105mph trap speed on 26 inch tire I will be turning ~5850rpm when I cross the line

Even if I were to run 110mph I would still be looking at ~6115 rpm. So I'm right where I want to be when I cross the line rpm wise with the 4.30's. I can always fine tune with different sizes of slicks, I could go to a 27 or 28 inch tall tire to drop the rpm some if I needed to.

The last reason I chose 4.30s and not 4.10 for my setup was because I do a lot of around town driving at 45-50mph.

I felt with the 4.10s I would be in and out of 5th gear a lot around town. The last thing I wanted to be doing was constantly downshifting to 4th if I have to slow down a bit say to 40mph. It is made worse because there is such a wide ratio between 4th and 5th in my trans. With the 4.30s I can cruise around town in 5th at 50mph and keep the rpm at ~1700. Not too high, but enough to cruise around comfortably without having to downshift everytime I need to let off the gas.

Obviously your trans ratios will be quite a bit different, but these are things you should be considering when choosing your gear. Fool around with the rpm calculator till you find a gear that will fit your needs.

 

[fiveoho]

‘preciate all the info on that mikemustang. Im thinking the tremec either comes in a .68 or .82 overdrive ratio. If it’s the .68, my calculations would be right with a stock T5 if I done 4.30s , right? But will the tremec gear set probably differ from a stock T5?

Im not sure what the gear set would be in the tremec?

Overlook my ignorance: if I have a .68 overdrive ratio, does that act as a lower gear? Or would the .82 be lower?

 

[blackcloud50]

Overlook my ignorance: if I have a .68 overdrive ratio, does that act as a lower gear? Or would the .82 be lower?

transmission gear ratios follow the same premise as ring and pinion ratios. In other words, the .68 is like 3.55 and .82 is like 3.73 for an example. Hope that helps you understand.

 

[fiveoho]

transmission gear ratios follow the same premise as ring and pinion ratios. In other words, the .68 is like 3.55 and .82 is like 3.73 for an example. Hope that helps you understand.

thanks. i understand now

 

[Redrooster]

just had alot of ppl tell me how didnt make the best choices......heads are too big. cams too big. intakes too small

just frustrated bro. i just hope it comes out better than what other ppl think

Which cam did you decide to get? I would stick with the 3.55's for a while. See how they do with your combo. If you need more gear you can always change. If you haven't changed it already your tremec has a lower 1st gear ratio than your stock t-5. In 94 the ratio went to 2.95 where it had been 3.35 in earlier years. the tremec has a 3.35 first. It will leave much better with the 3.35 first gear than it does with a 2.95.

 

[fiveoho]

Which cam did you decide to get? I would stick with the 3.55's for a while. See how they do with your combo. If you need more gear you can always change. If you haven't changed it already your tremec has a lower 1st gear ratio than your stock t-5. In 94 the ratio went to 2.95 where it had been 3.35 in earlier years. the tremec has a 3.35 first. It will leave much better with the 3.35 first gear than it does with a 2.95.

so the tremec will make it a little quicker off the line , compared to the T5?

will this be a noticeable difference?

 

[Grn92LX]

so the tremec will make it a little quicker off the line , compared to the T5?

will this be a noticeable difference?

The tremec has a 3.27 first gear. A t5 has a 3.35 first gear. The motorsport t5z has a 2.95 first gear. 5th gear is .68.

 

[blackcloud50]

so the tremec will make it a little quicker off the line , compared to the T5?

will this be a noticeable difference?

yes you will have an improved take off..not sure how noticeable.
Stick with what you have until combo is all together and then swap gears if needed. No since in spending money if its not needed right now

 

[mikemustang289]

yep, the tremiec gear ratios are 3.27, 1.98, 1.34, 1.00, 0.68,

I think 3.73's would be a good choice for street/highway use but at the same time they might not be what will get you the lowest e.t. at the track. It all depends what you want.

 

[blackcloud50]

yep, the tremiec gear ratios are 3.27, 1.98, 1.34, 1.00, 0.68,

I think 3.73's would be a good choice for street/highway use but at the same time they might not be what will get you the lowest e.t. at the track. It all depends what you want.

Which Tremec are u speaking of?

 

[fiveoho]

Which Tremec are u speaking of?

3550

 

[blackcloud50]

3550

my bad..I was thinking of the newer TKO500 who's gearset is slightly different

 

[fiveoho]

my bad..I was thinking of the newer TKO500 who's gearset is slightly different

so switching from a T5 to a 3550......will the 3550 still be to my benefit for a little better bottom end?

 

[blackcloud50]

so switching from a T5 to a 3550......will the 3550 still be to my benefit for a little better bottom end?

depends on whether or not your stock T5 for your year came originally equipped with 3.35 or 2.95 1st gear ratio

 

[fiveoho]

depends on whether or not your stock T5 for your year came originally equipped with 3.35 or 2.95 1st gear ratio

hmmm....good question

 

[fiveoho]

i know you guys said to kinda wait till i got the combo done and drive it with the 3.55s and just see how they do....which makes sense. why spend $$ now if youre not totally sure you have to later?

but- heres the thing. im very picky on who works on my car. my mechanic stays booked. wrenching is more a hobby for him, he has another full time job. i got a feeling that if i think theres a good chance i need to change the gear, better do it while the motor is being done or it may be a long while before i could do it.

aside from that, looking at my combo and keeping in mind that i will be doing a 3550 trans: what sounds like it might be the better choice? 3.90s or 4.10s?

this is a weekend car but i do want to be able to live with it as far as driving around town. like i said before, im just afraid if i do 4.10s, my 5 speed will become a 4 speed. i guess one of the main reasons i considered a 4.10 is because its a ford product. Motive makes the 3.90 gear im thinking of....i dont know the quality of it


thanks again for all your posts / help. keep them coming

 

[Grn92LX]

If you're going to switch, 410's are what you want. No offense but this isn't rocket science. The difference on the hwy between a 390 and a 410 is maybe 100 rpm's. Your heavy very needs the gear. Like I said, i'll be doing 430's in my pump gas street car and yes it see's the highway