Butters "Winter Upgrades". . Starting a Little Early

[Map63Vette]

Nice. What about with the 3.27 gear?

As I recall, the issue with the 8HP70 with a deeper gear in the Challengers was the motor redlined too fast for the trans and it hit the rev limiter in 1st. But that might have been with a 3.91 6M gear, too. I don't remember anyone talking like it was shifting too soon driving around normally.

This sounds familiar to me with some of the Challengers my dad has had. I don't remember the exact year, but I want to say he had a 2013 5.7 and he now has a 2016 (I think, maybe newer) 6.4 Scat Pak. Both manuals, but I think they both hit the top end of first way too fast to be useful. You didn't even get time to see a shift light and I'm not sure the traction control could tame it in time. Maybe different if you had really sticky tires that could load it up harder though.

 

[DionR]

This sounds familiar to me with some of the Challengers my dad has had. I don't remember the exact year, but I want to say he had a 2013 5.7 and he now has a 2016 (I think, maybe newer) 6.4 Scat Pak. Both manuals, but I think they both hit the top end of first way too fast to be useful. You didn't even get time to see a shift light and I'm not sure the traction control could tame it in time. Maybe different if you had really sticky tires that could load it up harder though.

I had a 2015 R/T 6M and I didn't have a problem with 1st that I remembered. It was fast, but no real traction issues unless I really got on it and kind of dumped the clutch.

I've even been planning to set my '73 up with functionally the same gearing. Bought my T56 Magnum with the same ratios and depending on the tire I run (275/40R18 or 275/35R18) I will run either a 3.73 or a 3.55 and end up matching almost perfectly.

 

[Map63Vette]

Gear ratios were one reason I went with the T56 when I did my swap. I liked the ratio spreads on my old 833 4 speed and a lot of the other modern options I was looking at had really weird spreads to me. Either stuff like a really short first gear (something silly like 6:1 that wouldn't even make it across an intersection before needing to shift followed up by a 2:1 second or something like that), or very little difference between some gears and inconsistent rpm drops. I was looking at stuff like the TKO, T5, T56, Passon 5 speed, etc (this was also 10+ years ago). I also specifically wanted the Viper T56 because I wanted the 0.5:1 6th gear. That was a problem with a lot of the other overdrive transmissions as well, the top gear was barely even an overdrive. I think some weren't much more than 0.96:1 or 0.85:1 or something like that. Not enough to make a difference in my book. The Viper spec T56 was basically an 833 with 2 extra gears and had really nice consistent rpm drops between each gear. With autos and a lot more gears to play with I don't think the ratios are quite as easy to compare. With a manual I didn't want to be shifting back and forth all the time trying to find which gear I wanted.

 

[Dantra]

I kind of like the 2.73 for the strip, should cross the line at the top of third and save a shift over the 3.08 gear. But the 3.08 would probably be better for autocross assuming it is held in 2nd gear. But I am just guessing on both.

Either way, I think it comes down to what is available. If the 2.73 isn't available then it is kind of a mute point.

My last trap speed was 113 and I have to suspect that's going to change.. It's gonna hit 4th, I'm sure.

If I have to find a set of used 2.73s, it's not that big of a deal.

Nice. What about with the 3.27 gear?

As I recall, the issue with the 8HP70 with a deeper gear in the Challengers was the motor redlined too fast for the trans and it hit the rev limiter in 1st. But that might have been with a 3.91 6M gear, too. I don't remember anyone talking like it was shifting too soon driving around normally.

This is my fear.. I'm wondering what can be done with torque management by my tuner

I think the main problem with deeper gears is going to be traction. The stock 6.4 could already blow tires off a dart, with this new beast I think the higher gearing will help make it more controllable. Just spitballing here. I only have 3 speeds currently and I already know traction will be a huge issue on the autocross.

When I had the 904 in, my 1st gear was a little boggy with 3.27s... I didn't spin a tire at all on launch with street tires and I just held it in first at Moparty. It wasn't the good 904 tho.. and it was wounded.

 

[DionR]

A 2.73 vs a 3.27 isn't as bad as going from a 3.06 to a 3.91 like the guy in the Challenger or Charger did. That's only a 20% jump compared to a 28% jump.

My guess is that a change in shift rpm for 1st gear would be enough to make it work.

I will see if I can the original post.

 

[Dantra]

A 2.73 vs a 3.27 isn't as bad as going from a 3.06 to a 3.91 like the guy in the Challenger or Charger did. That's only a 20% jump compared to a 28% jump.

My guess is that a change in shift rpm for 1st gear would be enough to make it work.

I will see if I can the original post.

I called my guy at FRP.. He said the 3.08s will work good. Ryan is able to massage the torque management and really make it work without completely blowing the tires off all the time. His (Isaiah) personal truck has 3.91s/28" tall tires, in the 11s and not slipping the tire at all with radials... launching in 1st. It's all in the tune

 

[DionR]

For what it's worth, a 3.27 with a 26" tire still isn't as bad as a 3.90 with a 28.68" tire. You would have to run a 3.55 gear to equal it when factored for tire height.

I bet you would be fine with the 3.27 gear, but I would guess a 3.08 would be better.

 

[Dantra]

For what it's worth, a 3.27 with a 26" tire still isn't as bad as a 3.90 with a 28.68" tire. You would have to run a 3.55 gear to equal it when factored for tire height.

I bet you would be fine with the 3.27 gear, but I would guess a 3.08 would be better.

That crossed my mind too.. I've been wanting new gears anyway. These have a slight howl to them when either on the gas or off. Typical Yukon gear, it seems. After talking with a few Ford guys, FoMoCo is the better gear for the 8.8.