Shooting the breeze. What’s the 1/4 mile time of a 340 challenger?

[kawahonda]

Wanted to ask you guys about rear-ends.

I understand that dr. diff sells complete sets with the Eaten clutch-less posi for about $1500. Do I know if I need the 7290 or the 1350 U-Bolt? I'm assuming that I have the OEM Mopar Adjustable tapered roller wheel bearings.

I'm wondering if there's other options that are easier on the pocket book, like perhaps a used drop-out. What specs are I'm going to want to look for if considering this route for a my 70 Challenger?

Still determining on 3.73 or 3.91. I've already thought through that this car may never really see much of the interstate, and the furthest I'd take it is probably an hour away, highway driving.

[1 Wild R/T]

People these days are soft.... You've got a 340, they like RPM's so give it more gear & enjoy the fun....  Back in the 80's I drove a 440-6 Challenger with 4:10 gears from central California to San Diego & back.... Only thing it hurt was my wallet.... 

Running a 340 I wouldn't hesitate to use 3:91's or even 4:10's..... Maybe even 4:30's (I used 4:30's in my brothers Edelbrock headed 340 Challenger.....  But I also used a 518 trans....

Want an example of what lots of gear drives like? You have 3:23's now right?   Take it out on the highway rolling along at 65ish & drop it in 2nd gear.... 3.23 x 1.45 = 4.68.... Yeah, 4.68 gears.... Your 340 should be fine driving in second gear for an hour.... 

[nsmall]

I have a 340 and a 727 and 355's seem great for the highway and mostly in town driving. 391's sound more fun. I bought a used 741 or 742 (I forget) case with nice used 355s, all new bearings and a new dr diff sure grip for $800 total.  Isnt Dr Diff in MT?  Maybe you can make the drive to save on shipping. 

[RUNCHARGER]

I think the 3.91's are pretty streetable with a 340 as well.

[kawahonda]

I don't think I'd want to go any higher than 3.91. That's even a stretch I think, but I'll keep my 3.23's for if the need to ever "drive it far and away" comes up. even 3.23 is not all that of a tall gear.

Let's say 65 MPH is going to be a good cruising limit to dial everything in. Car shouldn't see it often, but that's a good speed to keep it highway-able.

w/ 3.23 and 26.1 OD tires, at 65 MPH I will be pushing 2700 RPM.

w/ 3.73 and 26.1 OD tires, at 65 MPH I will be pushing 3120 RPM.

w/ 3.91 and 26.1 OD tires, at 65 MPH I will be pushing 3275 RPM.

I wonder if 3.73 would also be a good option? My current case is a 489 case. I suppose if I were going the "used" route, than any 489 case will do? The nice thing about doing a center section swap is that it would be a good time to repack my wheel bearings.

[kawahonda]

Regardign ratios, EL5DEMON340 had a really good post that gives some guidelines. It's the best I've seen:

Daily driver and lots of highway = 2.96, 3.23, 3.55
Weekend cruiser with a good amount of highway = 3.55, 3.73
Weekend cruiser or daily with very little highway= 3.55, 3.73, 3.91
Weekend cruiser or daily with no highway and short trip= 4.11, 4.30, 4.56, 4.88, 5.13

[RUNCHARGER]

I ran 4.56 on the street and they are a bit of a bear. They blow the tires off without effort and on a 100 mile highway trip they keep your speed down to around 60MPH and it isn't all that fun.

[kawahonda]

I feel that 3.73s may be the ticket. 3.91s may be close to 3.73 gearing for people with a 28" tall tire, but since I'll be running 26.1" for quite some time....MAYBE slightly bigger in the future...I have questions that 3.91 may be a little too short in my case.

3.73 SHOULD keep your highway driving "acceptable" but not "great". It gives you good potential (I think) at the strip. And it provides the standard "two-step up to feel a difference" where it's worth the cost to do it.

My friend's 68 'Cuda  340 4-speed has 3.91s and while he loves it for the strip, he said he's annoyed with it after often, but short highway usage. He drive's it about 10 miles into work most days of the week in 55-65MPH speed zones, and he's had that gear set for 10 years. He's worn down by it and wants to put 3.55s in.

He did say that I would likely be "OK" with 3.91s if I want to drive it on short highway trips (up to an hour away) once in a long while. The question is, if I'm already set on 3.73, is 3.91s that much worse? Looks to be 155 RPM worse...which seems like "not much".

Does going to 3.73 to at least give it somewhat of some highway manners close me out from hitting solidly in the 13s compared to 3.91 is the question....

[HP2]

How about you have some 28" tall street tires and some 24" tall race tires. Two pairs of tires and a couple steel rims are mucho cheaper than gear replacements or purchasing a second 3rd member.

[kawahonda]

HP2: The reason is that it breaks the "looks" department for me. Most of the time, I want it to look like a stocker. Having 28" tires on the back to me looks a bit hideous.....and I'd also have to get another set of rims that are at least 8". Right now I have 7" rims all around and 235's all around. The max I'd want to go on my rear 7" rims are 245, and that's only going to buy me .5" taller which doesn't do much to the RPM calculator.

I see your point though and totally get it and that's just a "way" to do it. I'd rather try to go as universal as possible and not have to "swap" out stuff.

I need a second 3rd member anyways. 3.23 gears are stinky for an auto, and it's an open rear end. Still going to need a new third member.

I'm more and more thinking that 3.73 would be a nice set for what I'm after.

[Cudakiller70]

How about you have some 28" tall street tires and some 24" tall race tires. Two pairs of tires and a couple steel rims are mucho cheaper than gear replacements or purchasing a second 3rd member.

That's simple and smart, tall tires for travel, small for short trips and around town fun! Good thinking right there.

[HP2]

HP2: The reason is that it breaks the "looks" department for me. Most of the time, I want it to look like a stocker. Having 28" tires on the back to me looks a bit hideous.....and I'd also have to get another set of rims that are at least 8". Right now I have 7" rims all around and 235's all around. The max I'd want to go on my rear 7" rims are 245, and that's only going to buy me .5" taller which doesn't do much to the RPM calculator.

I see your point though and totally get it and that's just a "way" to do it. I'd rather try to go as universal as possible and not have to "swap" out stuff.

I need a second 3rd member anyways. 3.23 gears are stinky for an auto, and it's an open rear end. Still going to need a new third member.

I'm more and more thinking that 3.73 would be a nice set for what I'm after.

Different strokes. Just throwing out ideas for consideration. Ultimately, its your ride and your wallet, so you have to do what makes you happy.

[Crash520]

Yep still has factory bumpers, I do have an AAR hood on it.
I can't get it to rev past 5300 due to valve float, it has cupped seats and bad guides, trans has a shift kit installed, I have a D60 from a truck so have fitted Caltrac bars to control spring wind up.
I'm using FAST XFI SPORTSMAN EFI, so that controls timing which is around 32*. It's a tired motor and I haven't had a lot of time to really dial in the EFI

[kawahonda]

Do you guys know if my Challenger has the 7290 U-Bolt or the 1350 U-Bolt?

[GY3R/T]

Do you guys know if my Challenger has the 7290 U-Bolt or the 1350 U-Bolt?

Do you mean u-joint ?   7260-7290 ?