can somebody compare 3.42 and 3.73 gears for me? like acceleration, gas mileage, and anything else about them. also, which do you have/like better and why. thanks.

 

It's not really going to make much of a difference. Now 4.11s would make a difference.

 

well 4.11s are more of a racing type of gears im looking for street performance

 

Highway cruise rpms will go up 2-300rpms about. Gas mileage will go down a bit. You will notice a bit of a increase in acceleration but not enough to really care about. First gear will be pretty useless. Honestly ive found for a street driven car that 3.23/3.27 and 3.42/3.45 to be the best ratios. I had 3.42s and actually went the other way to 3.27s to gain a bit of highway cruisability. I dont race my car but on the street i really didnt notice too much of a lose going to 3.27s. Maybe slightly but again not enough to care about. In fact i might have gained a bit cause now its a bit less likely to burn out...and instead just pins me to my seat and doesnt let up.

 

ooo so with the 3.27 i think you said it was unless you tried to do a burnout it didn't?

 

3.42 or 3.73 gears would be a good choice for all around performance and highway economy, if you have a 4-speed trans, which I assume you do. Probably won't notice that much of a difference between the two, however, I would opt for the 3.73. I've had experience with that ratio and it's a pretty good one. However, if you have the borg warner 9-bolt, you won't find this ratio. You'll find a 3.70 ratio. If you're planning on swapping out gears from a rear end with a lower ratio, like a 2.77, you'll have to upgrade to a three series carrier. 3.23 or above requires a 3-series carrier.

The 3.70 or 3.73 will get you up into the power range faster than the 3.42, but only slightly. This will give you better acceleration.

 

It will do a burnout just fine. It just is easier to get it to grip off the line and pull hard. The 3.42 wanted to just do burnouts if i stabbed the gas wrong.

 

I run 3.27 gears with a 5.7 and agree that they are really good gears for the street. Great acceleration with minimal tire slip off the line. With a 4 speed auto (OD) Im running around 2500 RPM at 65-70 mph.

 

I've read alot of posts recommending 3:42 for the 700R4 auto. I have a T5 and went from 3:08 to 3:73 when my posi went in. I find it too much. 1st gear is only useful for starting on an incline. If I had to do it over again I would go for 3:27 or 3:42.
Jon

 

I'm not trying to hi jack this thread but I have 2.77's in my 9 bolt & really want something higher (or is it lower) but I didnt know if 3.27's would be noticeable enough, I was thinking I would have to go to a 10 bolt with 3.42's what do you guys think?

 

i thought that 3.73's ran around that. the smaller the gear the lower your rpms are at a higher speed. like 3.73s are at about 2400 at 65 mph. or so i thought. Anyway so 3.42s will get you better traction, and minimal mpg difference. and 3.73 will allow the wheels to spin easier, and accelerate slightly better than the 3.42s correct?

 

I went from the 2.73 to the 3.27, but I want a 3.42 4th gen rear for the torsen posi unit, bigger brakes, and slightly more aggressive gear ratio.

I didn't notice any difference in mileage when I went from 2.73 to 3.27, but acceleration did get a little better. I do about 95% city driving.

Mike

 

yea but what did you do about the 4th gen rear being 2 inches longer?

 

I haven't got the 4gen rear yet. I said that is what I'll be going to next. When I do get it, I'll just be getting either 4gen or corvette wheels as 17"x9/9.5". Not sure yet on how wide I'll go. I'm just having trouble finding a local rear end so I don't have to pay like an extra $100 just for shipping.

 

well won't you mind that still the tires will be sticking out the body?

 

4th gen or Corvette wheels on a 4th gen rear end will sit under the car the exact same way a 3rd gen rear with 3rd gen wheels will. The wheels will still have the same outside width, but because the wheels/tires I want are wider, they will just extend inward more then my current all 3rd gen setup. Does that make sense?

Mike

 

ok yea i see what you're saying. correct me if i'm wrong: a 3rg gen rear with 3rd gen stock wheels and tires is the same length as a 4th gen rear with 4th gen wheels and tires. what size gears are in a stock 4th gen rear. not quite sure if you already said that in here or not.

 

You are correct.

The only ratios offered in the 4th gens was 2.73, 3.23, and 3.42. As far as I know, those were the only stock ratios.

 

is a 4th gen rear a direct exact same fit. no customizing or nothing? the driveshaft and brakes and everyhting will 100% hookup without customizing?

 

Direct fit, yes, though you might have to do some fabbing for the e-brake if the rear is 98+.

JamesC

 

i have 3.73 gears in my rear and they are amazing! i highly recomend them. dont nworry about gas in cars like these just be happy its still alive! they are aggressive fine on the highway and fun as hell in a parking lot without going too crazy on the street with 4.11's

 

the omly thign im worried about is mpg with 3.73s. what are you guys getting?

 

I don't bother looking at mpg anymore. With a V8 it'll just make you crazy. I don't see alot of highway miles so there really is no difference at all if you're driving 'economically'. If normally on a given road you would be driving in 4th well no you'll be in 5th. In some instances you'll actually be cruising at a lower rpm.

If you're accustomed to driving distances at 70-75mph then you'll really notice the gas consumption. But at 60-65mph it won't be a real issue. Better yet, throw in a T56!

I'll reiterate my previous post and SubIroc as well by saying that while 3:73s are a good street gear and will allow you to get into the high torque portion of your power band earlier it can be difficult to make it usable. You'll probably be quicker of the line (less wheel spin) with the 3:42s.
Jon

 

well i have a 700r4 so i think i may go 3.73 but i am still undecided

 

​​​​​​ how much HP are you putting out to trans? im doing save set up, i have 3.42 now snd going to 3.73 with posi, what did you not like about the 3.73?

 

I had 3.73 and went 3.42 I also swapped my 5th gear from .72 to .63. About 2/3 of my commute is on the expressway and it saves some RPMs. I am about 250 rpm lower thanks to the rear end and about 400rpm total thanks to the two together. I am getting about 17mpg combined with spirited driving with a 350 and sniper efi. I dont notice a huge acceleration change. Who knows if I have to rebuild the rear again I might try 3.73 but I really dont care.

 

Forgive me for jumping in here and would really appreciate help.. I have a 56 Ford Courier with a 233 and a 3 on the tree. I have an 8" rear and only can get a top end of 55 mph. According to internet specs on this car I should be getting over 90 mph. Engine runs great. With my setuo I should have 3.7 ratio. What gear ratio should I have to increase hwy speeds. Thanx much!

 

This is not a Ford forum...

 

For a 5 speed, I really like a 3.27, maybe 3.45. ....for a 700r4, I went from a 2.77 to a 3.27 and it made a difference without sacrificing notable cruise rpms/gas mileage. Then I swapped in a 2200 stall converter and that made a HUGE difference! 3.27 and a 2200 stall was FUN combo.

 

I run 3.73s but 3.23s or 3.42s would be better. 1st gear is almost useless