Looking for a better rear end gear ratio for cruising speeds. Current set up is 410 gears, TF 904 with a 2000 stall and 25.5in diameter tires, which screams at 4k rpm around 70 mph. Ideally I would like to be around 2,500 rpm at 70 mph.
Gear Ratio Recommendation
- Thread starter Mcfarlrm
- Start date
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2.76 - 28” tire
What’s the rest of the engine like, parts wise?
What’s the rest of the engine like, parts wise?
Thanks. The only problem is the description “Mild Cam” has no meaning since it is an opinion on what a mild cam is.
If you have cam specs, or know the grind number/model number of the camshaft, please provide them.
If you have cam specs, or know the grind number/model number of the camshaft, please provide them.
MidnightSwinger
Well-Known Member
2.76 according to spicers calculator
I used to have 2. 93 now I have 3.23. Both are no strain on anything
66Dartdriver
Well-Known Member
https://www.tremec.com/calculadora.php Here is a Tremec gear calculator.
3.23 is a great all around gear. 3.55 if you do more around town and less highway.
Unfortunately, I do not have that info. Came with the car when I bought it and didn’t get too much details from the previous owner. Is there any easy way of finding out without pulling the cam?
No, not really. There is a way, but it’s kind of involved ane more of a pain in the ***.
Don’t overthink it. Just buy 3.23s with a sure grip. You can thank me later.
33IMP
Well-Known Member
Agree with Dental Dart. I think the highest gear you can get new for an 8 3/4 (lowest numerically) is a 3.23. It is an excellent compromise gear. Probably why they were stock ratio in lots of performance Mopars.
Another one that recommends 3.23's here.
2800 rpm at 70 is doable on my end. I'm putting more around town than anything. Would be nice to have this set up for when I want to travel some distance. The wheel diameter I had mentioned previously was incorrect. The P255/60R15 102S M+S BFGoodrich Radials I have are 27.1" not 25.5".
chrgdrt
Well-Known Member
2.76’s came in 8 3/4s. My barracuda came with a2.76 peg leg,but I did swap it out for the 3.23 sure-grip I had.
I do like the 3.23 better the 2.76 was just too long legged, great if you want to do alot of freeway flying.
this is with 26” tires
I do like the 3.23 better the 2.76 was just too long legged, great if you want to do alot of freeway flying.
this is with 26” tires
MidnightSwinger
Well-Known Member
Yes
Sure there will be a bit less low end grunt, but for a probably close to stock 360 the 4.10 is less than desirable. Gearing is just part of the equation.
MopaR&D
Nerd Member
I second this, your stock-ish engine likely can't wind up quickly enough to make full use of the short gear ratio. It won't rev out as quickly with the 3.23s but your overall acceleration won't be much worse. I once tried 4.10s behind a mild-cammed (213 @ .050 on 112 lsa) 360 and it was too much. 3.55s would have been ideal which is what I now run behind my current somewhat hotter 360 (ported Edelbrock heads and bigger but still mild hyd roller cam).
I have always heard that the 3.55 is the best compromise ratio. I have that in my 71 Demon 340 and to me, it's not enough gear for performance and too many rpms for higher speeds. Kinda the worst of both worlds. I have 4.10's in my avatar and my 69 Charger but neither are highway cars.
Personally, I think you're going the wrong way. An OD transmission is a better choice, IMO and leave the gear in there you have now.
....and 3.55s? That's the pussiest gear you can ever choose IMO and here's why. It's too low for any real highway cruising, as the RPMS will still be fairly high and they are too high for really any kind of real performance driving. IF you stick with a non OD transmission, the lowest gear I'd use would be a 3.23 if you want to retain some semblance of decent cruise RPM, but a 2.94 or even 2.76 would be even better. Just one peon's opinion.
....and 3.55s? That's the pussiest gear you can ever choose IMO and here's why. It's too low for any real highway cruising, as the RPMS will still be fairly high and they are too high for really any kind of real performance driving. IF you stick with a non OD transmission, the lowest gear I'd use would be a 3.23 if you want to retain some semblance of decent cruise RPM, but a 2.94 or even 2.76 would be even better. Just one peon's opinion.
Dartswinger70
Well-Known Member
Bin wantin' - ta have 3:91s now...
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Couldn't agree more Rusty! That's what I was trying to say. If I was interested in any type of performance in my 71 Demon, it would have more axle ratio and a much looser converter. The only true way to have your cake and eat it too is an OD trans. This let's you have the higher axle for launch/acceleration and the lower rpms on OD on the highway. There's no free lunch!!
Lol I want 3.91s but it’s not a great highway gear
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