Just to get away fro mmy other thread so that everyone will read this:

I ordered some 3.73 ford Racing gears with an Auburn Limited SLip differential, I am wondering if I will regret not getting the 4.10s, I can get the 4.10s installed at the shop and simply return my 3.73s to Summit, but I dont know what I should do. Is there a big difference in accleration between 3.73s and 4.10s, is it something I would feel and show up on my 1/4 mile times? I know that with my 27.9" tires, at 80 mph the 3.73s = 2516 rpms the 4.10s = 2765 rpms. This truck is my daily driver, and i dont take it on the interstate that much, but next year with going to colelge 60 miles away, it will see more interstae use and Iam wondering what I should do. I dont want to put the 3.73s in and not feel much of a difference and be really disappointed, will I be? Help me make my decision guys. Thanks

 

I think you made the right choice with the 3:73's since it is a daily driver and will be seeing more interstate use in the future.

 

Keep in mind you're only dealing with an extra 250 RPM at 80 mph. Most of the time traffic will keep you below that anyway.

When you look at the ratio difference the jump from 3.73s to 4.10s is about 3/4 of the difference between 3.31s to the 3.73s. More than anything I would take a look at a gear calculator and see which gear set would put you right back in the fatter part of the torque curve after shift points, and especially the 2-3 shift point.

With limited highway use such as your case I would probably jump right to the 4.10s. Once again use the gear calculator, but 4.10s in overdrive won't have the revs much different than your 3.31s in drive on the highway..... it would be close enough to see if you could tolerate that rev level for the highway use you have.

 

Absolutely the 4.10's!!!! Considering the added weight of your vehicle (5k+ lbs.), your transmission (auto), and your desired results (win some races). Bro, it's a no brainer, IMO.

4.10's

Take care,
~Chris

 

im with PKRWUD on this one, i have 3.73's on mine and if i could do it again i would DEFINITELY get the 4.10's, no doubt about it. believe it or not, the difference between 3.73's and 4.10's is pretty big (im saying this after comparing my truck with a buddy of mine's truck that's identical to mine, except his is 4x4 and has 4.10's).

 

Yeah yall are starting to sway me, and I think I might go that route, I still have to decide. You are right about not usually being able to go 80mph, I guess around 70 is the norm. I was looking at that, and going fro ma 3.31 to a 3.73 isnt that huge of a difference, but going from a 3.31 to 4.10 is. How mcuh can I expect 4.10s to drop my 17.16 1/4 mile w/ 2.44 60ft time by, if I have traction, could I be lookign at a mid 16 second pass with 4.10s and just a high 16 second pass with 3.73s? I really dont want ot regret my decision so Iam trying to get all the info now. Also the shop I am going to use deals with Precision Gears, are those any good?

 

Precision Gear is as good as it gets.

I've got 3.73s in my truck, but it's a 300. It has a much lower torque peak than your 302. I wanted to be at my 2000 RPM torque peak in OD at 65 for highway towing. I missed by 9 RPM, I'm at 1991

With a 302, I'd have gone with 4.10s in a heartbeat, but I'm running 30" tires. With your 28" tires, you're about equivalent to a 4.00 with my tires or about a 3.86 with the stock 29" tires.
It's sort of a tossup. You'll like the 4.10s better every time you mash the throttle and like them a bit less every time you're on the Interstate. There should be little or no net mileage difference between the two. If you EVER tow you'll want the 4.10s for sure.

 

Some info I put together:

3.31
70 mph - 1953 rpms
80 mph - 2232 rpms
1st - 41 mph (4600 shift)
2nd - 68 mph (4200 shift)
3rd - 101/114 mph (4000/4500)

3.73
70 mph - 2201 rpms
80 mph - 2517 rpms
1st - 36 mph (4600 shift)
2nd - 61 mph (4200 shift)
3rd - 89/100 mph (4000/4500)

4.10
70 mph - 2491 rpms
80 mph - 2765 rpms
1st - 33 mph (4600 shift)
2nd - 55 mph (4200 shift)
3rd - 81/91 mph (4000/4500)

With the 4.10s at 65 I would be turning 2247 rpms in OD, so this is like 150 shy of what my peak is supposed ot be at, so does this mean I would be able to tow in OD?

 

I was taught to never tow in OD, but what do I know?

Please, please, get the 4.10's. Stop tormenting me and just do it, dammit!



I will never forget how much my butt puckered the first time I got on it in my 69 Chevelle SS when I switched from 3.08's to 4.11's. I still haven't completely gotten the smile off my face, and that was 20 years ago.

 

I wouldn't tow in OD unless it was a fairly light load. It isn't available torque that is the concern, it is putting the extra load on the lockup clutches..... not a strong point in these trannys.

Look at the gear thing this way. Going to 4.10s over the current 3.31s at a given speed your truck will pull almost as hard in 4th as it now does in 3rd. If you're really looking for the performance it's a no brainer.




Chris,

This is too scary. I also had a Chevelle. In my case it was an SS body/chassis with a 307 and Powerglide in it when I bought it. Primered ready for paint and a semi crappy interior. It took a while, but this was replaced with a 396 and a Muncie 4 speed. Major pucker power!

Without much traction we got it mid 12's on the build. Played briefly with nitrous, went back to sorting it out NA. Sold the car to a friend that helped me with a lot of the wrenching when I went in the military. With the suspension sorted better and some traction he broke into the upper 11's.

I learned the hard way what a big bumpy cam is like to drive on the street in traffic...... darned if that old guy wasn't right about that. It was worth it on cruise nights though!

 

It's OK to tow in OD as long as the tranny doesn't hunt back and forth between 3rd and 4th. If it pretty much sticks with OD except for big hills, you're not hurting a thing. My tranny temp gage actually shows slightly lower temps in OD than in direct.

 

Well the gear guy convinced me ot stay wit the 3.73s since I will be seeing more highway use. I amy happy wit hthe decision. A friend who has a truck similar to mine except regular cab has 4.10s and when he is in 3rd, the rpms are out of the hp/tq curve and he isnt pulling hard anymore, and he suggested I get the 3.73s. I got it installed and everything is great, except my speedo is jumping around again, because in my rear end, Ford had left a thin welding rod in there, who knows how, and it was like the consistancy of 20# test monofilament, and that was wrapped around the exiter ring, which I believe is what sense the speed, and it was wrapped around some gears in the open diff and it had warped the exiter ring, but it was i na fairly straight line and that was what my speed sensor was reading, the wrapped rod, rather than the ring, so when he pulled all of that apart the ring is what looks like if you took a hammer and hit it a few times and the "sproket" lets call it, bulges like 3 times, so now my speed jumps around at all speeds. The guy said he would take a look at it, but is convinced that the speed is read from somehting in the tailshaft of the tranny, but I insisted it was that ring, and with those bends in it, it wouldnt read right, thus the bouncing speedo, and I was right, I will see if he will put a new ring in there. Is this were the speed is read?? I also have to wait 400 mile for a breakin period, and he doesnt want me driving it more than 30 miles at a time, because it makes alot of heat, and I cant go on the interstate until 200 miles lafter his install, so I have yet to see if it made a difference, but from what Ican tell just going to 3k 2 times, it pulled alot harder. I dont like how I am in in OD at 35mph, but once the breakin is over, I will just turn the OD off until I am going over 45.

 

Well, 4.10's might put you above your torque curve now, but if you plan on getting heads, intake, headers and cam down the line, your torque curve is going to be much higher, but since you've already got the 3.73's there's no use thinking about it now. BTW, I wouldn't recommend driving in OD at 35 mph. That's how you shorten the life of your tranny. Just ask the previous owner of my truck who used to drive in OD in town and had to get a rebuild at 70k.

Any ways, I hope you're happy with your gears and LS. Let us know what you think after your break-in period.

 

That "gear guy" you took advice from doesn't sound like he knows very much. hey, as long as you're happy, that's what counts.

 

What do you think I should do instead? Not taking it hard, just going up to like 3k, the truck pulls really hard I like it. I cant wait till I floor it.