.

 

3.90 is better for street, and if you dont have absolute slicks, you would probably not need 4.10 gears
you would only go bigger gears if you were bogging, or not at your peak power as you cross the line in 3rd

 

I would say for mostly street and strip that 3.90 is almost too big. For that tranny and that engine i wouldnt go bigger than 3.73. Thats just me though. With 3.90s first gear will be almost useless and the tranny will be through first gear in a blink of an eye. There is a calculation somewhere online that can calculate the ideal rear gear for your combination. You might find that what gets you off the line and through the traps fastest is a 3.42/3.45 or 3.70/3.73.

 

They make a 3:90 gear for a GM small 10 bolt???????

 

Yup

http://store.summitracing.com/partde...5&autoview=sku

 

Having the cam specs or better yet a dyno if you have one. By the power estimate you have, 108mph is what it should do at the end of the 1/4. Ideally the rpm at the finish is somewhat close to, but not passed the rpm where peak hp happens at.
3.90's w/26" tire 108mph: 6000rpm
3.90's w/28" tire 108mph: 5600rpm
4.10's w/26" tire 108mph: 6300rpm
4.10's w/28" tire 108mph: 5850rpm
I've always liked the 3.73 gear that always seems to get it either good or close enough, but I'm guessing the 3.90 will be good for your car without knowing anything else.

 

have no dyno or 1/4 mile times yet. i do have a 26in tire. And here are the cam specs

http://store.summitracing.com/partde...2&autoview=sku

Its more of a top end cam

 

That cam will probably make peak power around 6200-6400rpm, so the 4.10s would be on the edge of too much. I'd go for the 3.90s that leave room for more mph without needing to change anything, along with being a little more street friendly.

 

I have 3:73s in my car with a 305tbi lol i think its fun i never really go past 80 mph and its fun i say go with the 4:10s! Just my thought.
kevin

 

With the 3.90 will I still some street slick radials. I was planning on some for the 4.10's because I have heard horror stories about hooking up with them

 

I'm not sure if I get what you mean, but 3.90s will be easier to hook up than 4.10s. Really any car you want to drag race should have a sticky tire of some sort, unless the car is really slow, you don't mind spinning, or the suspension is really good. For instance, a 26" tall tire with my 3.73 gears will not hook, but a 28" tall tire will. When I used my old 305 at the end of the 2007 season the suspension upgrades let that use a 26" tall regular street tire and pull off a 1.8x 60' time.

 

Using the Drag 2000 program there's very little difference in 60', ET or top speed between 3.70 and 4.10 and a 700R4.
I know that's not the real world although it's interesting information.
There's more to be gained by using a close ratio transmission and eliminating the big change between 1st and 2nd gear.

 

There is some merit to this claim. Go with whatever gear will give you the best performance at the strip.

On the street, ive driven both a 3.90 and a 4.10 in 26" tires, and a TH350, and they both sucked equally for gas mileage. Nearly behaved identical. You probably wouldnt "feel" much of a difference between them at the strip either, but the ET will tell the tale.

 

Did you miss type or actually use a 3.70 ? I am wanting to know about 3.90 gear.
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And one last question If I end up blowing my 700r4 up this season and switch to a th350. Will my gear selection now not be good for a th350 ?

 

As long as you're still going to use an auto trans. the gear selection will remain the same because they all use 3rd gear as a 1:1 ratio.

 

Remember 26 inch tire is a neutral number. Meaning that with a 26 inch tire what ever ratio you put in the car will be exactly that and for ever inch size tire you go over or under 26 you will lose/gain .10 off the gear ratio. I.E. 4:10 with a 28 inch tire will be 3:90 in your final drive ratio or a 3:73 gear with a 24 inch tire will be a 3:93 in final drive ratio. Keep this in mind when you chose your gears

 

I was comparing a 3.70 to a 4.10. You can see that 3.90's would have even less difference.
As far as the TH350 compared to a 700R4, with the difference in the first gear ratios, 2.52 vs 3.06, you would need a 5.0:1 rear gear to get the same overall 1st gear ratio in the TH350 as compared to the 700R4 with a 4.10.
It seems the quickest drag racers use a close ratio trans like the TH350 and tons of rear gear to get the best ET. Not too practical for the street though when you consider an optimally geared drag car had a top speed equal to its trap speed.

 

Well i have made my decision to go with the 4.10's. Since I am going to upgrade to a 255/60-15 ET Street Radial and hopefully the fit. That will help me hook good on the street and put the 4.10 to good use.

 

275/60/15 would be just as nice, 28" tall.

 

295/50/15's fit with a little inner quarter panel work and look MEAN!!

 

I dont think Im taking a hammer to my car anytime soon. Just want something to fit in the space that I have nicely.

 

Perfectly understandable!