Changing rear gears?

[55 Tony]

Hi, I joined here years ago but never posted much, but I have a question. For the first time I took my 55 to a *sort of* dragstrip. Sort of meaning while closed and out of business they sold the tree and all timing and electronics but plan to get it again in the spring.

Anyway right now it's sort of what they call "street racing". A flag man and an orange cone at 1/8 mile LOL. I don't get much traction but I did manage to beat a vet! (and lost 4 others). OK so I sort of feel like this could be fun, so I'm thinking of changing my 3.42 gears to 4.11 or maybe go further. The thing is that I also like cruising on the interstate at 75-80. So I'm thinking of getting some slicks that are about 28" and street tires 275/70-R16 to keep the rpms down on the road. Any comments/suggestions if this sounds like a good plan or not?

The motor is a 454 that runs pretty well. Never dyno'd but the guy who helped me pick out parts when I rebuilt it said maybe 500 torque and 450HP. Thanks

[Rustaddict]

You're not gonna like the 4.11s an the interstate and you will probably there more than you are the race track. I don't think you can put enough tire on the back to get the rpms livable cruising at 75-80mph.

[zbad55]

Racing and cruising don't really work well together, you can always just change the pumpkin at the track to the 4.11 and then change it back when not racing. I know a few guys that used to do this in the old days.Just carry the extra pumpkin in a 5 gallon bucket,

[chevynut]

Go with the 4:11 gears and get an overdrive transmission. Best of both worlds. Tires aren't going to get you what you want.

[55 Tony]

According to the Wallace racing calculator, my current set up is (255/60-15 tires)
3000 rpm
3.42 gear
27.05" tire = 70.62mph

And with a 275/70-16 at
3000rpm
4.11 gear
31.16" tire = 67.69mph

That's not too bad. But I don't know what a tire like that will look like on my car?
My rear is a 12 bolt so no simple pumpkin change.

[zbad55]

OK, 12 bolt=no quick change rear end. As for tire size when I was running 15's, the largest tire I could get to fit my 55 was the 255/60/15. Not sure how your going to run a 275/70/16, I dont think you fit that diameter in the car

[55 Tony]

Go with the 4:11 gears and get an overdrive transmission. Best of both worlds. Tires aren't going to get you what you want.

Yes that would be great. I may be looking at pull-a-part for a 4L80E. I don't know if they disappear really fast?

[55 Tony]

OK, 12 bolt=no quick change rear end. As for tire size when I was running 15's, the largest tire I could get to fit my 55 was the 255/60/15. Not sure how your going to run a 275/70/16, I dont think you fit that diameter in the car

I had 275/70-15's on it and around corners they rubbed on the shackle around the springs, so I cut off the outside part of the shackle and left it on the inside. Or they may have been 265/70-15? Getting those or my current tires on/off requires disconnecting the rear sway bar and jacking it up by the frame. Actually since I added Caltracs, I just left the sway bar disconnected. The Caltracs do almost as much as the sway bar did.

[markm]

I have a 74 Z28 with 3.42 Super T10 and 255/60/15s and a 67 Camaro SS 350, Super t10, 4.10s and 275/60/15 they both suck @70mph. I built a drum to drum 12 bolt with a 3.07 gear for last years Power Tour. Now my performance sucks . Unless you go with 44 inch tall super swampers gears dont cut it alone. My 56 with a 3.42 57 Olds, 700R4 or 55 with a 3.54 Dana 60 and a TKO600 both run 70 effortlessly, however no matter what you do they are shoeboxes,

[Rick_L]

If you go to taller tires that negates the gear ratio, unless you have one pair for the street and another pair for the track. Either you put up with the 4.11s with your current trans or go to an overdrive trans.

As suggested, 31" tall tires won't fit your car no matter the width.

[55 Tony]

If you go to taller tires that negates the gear ratio, unless you have one pair for the street and another pair for the track. Either you put up with the 4.11s with your current trans or go to an overdrive trans.

As suggested, 31" tall tires won't fit your car no matter the width.

Yes Rick, as I said in the first post, I would get a set of slicks smaller diameter than the street tires. I'm not that dumb.

I don't understand why 31" tires won't fit? The only hard part is getting them on and off. Once on they have plenty of room. The one set of tires I had, I had to jack it up by the frame, then put a small bottle jack between the rear and the arch in the frame and jacked the axle down to get them on. A bit of a hassle but it worked.

[chevynut]

I don't think 31" tires will fit unless you move the axle rearward 1" or so. The tires will rub at the rockers. Besides, you're talking about a tiny change in RPM at a given speed, and as Rick said you'll negate some of the advantage of going to a lower gear. You really need an OD tranny to get good street/strip performance and still cruise the highway.

[Rick_L]

Based on my experience, 30" is the maximum tire diameter unless you move the tire/wheel inboard enough to clear the corner where the rocker panel meets the wheel cutout. And if you do that, you have to worry about clearance to the wheel tub in that general area.

[55 Tony]

OK thanks! Now I know where to look to see what you mean. And my rear by mistake happens to be 59". I had tires that rubbed the shackle on the leaf spring, so I cut off the outside edge of the shackle. They never rubbed in the wheel well.

And while I'm at it, is there a fairly easy way to move the rear back? My driveshaft is actually on the long side anyway. Is there a way I can drill a new hole through the springs to move the center bolt rear? Certainly not with any drill bits I have.

[markm]

4 Speed or auto a street strip 454 will respond to a good converter more than a gear change if auto. 4 speed a whole different animal.

[55 Tony]

4 Speed or auto a street strip 454 will respond to a good converter more than a gear change if auto. 4 speed a whole different animal.

It's th400 with a tci 240900. Supposed to be about 1000rpm over stock. I'll go one step at a time and first see what it does with slicks.
Cam http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=436&sb=0 Without slicks it has far more low end than can possibly be used. Guessing at 10.5:1 compression. Cranking compression is 205 - 215.

[55 Tony]

Another newbie to slicks question ... do I have to screw them on? Or just mount them.

[markm]

If you are going to run less than 15 psi screw them for sure . Never a bad idea.

[markm]

It's th400 with a tci 240900. Supposed to be about 1000rpm over stock. I'll go one step at a time and first see what it does with slicks.
Cam http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=436&sb=0 Without slicks it has far more low end than can possibly be used. Guessing at 10.5:1 compression. Cranking compression is 205 - 215.

A good 10 inch 3500 convertor with your 342 gears would out preform yours with 4.11s.

[55 Rescue Dog]

Not knowing what tranny, 1st-2nd gear ratios, tire diameters, trap speed, etc. there is no way to give a good idea as to the best setup for your goal. If running an auto, a better plan is a 4 speed for sure, and run closer to the same size tire for track or street. Need to come up with a combo that gets the most out of 2nd gear I would think. Running a non-overdrive 1:1 trans will always be a compromise no matter how you slice it, unless you have a quick change rear, which I have. I can pick from like a 100 different ratios, that can be changed in 20 minutes. This is a 1974 Frankland with a 4:86 10 1/2 inch ring gear with a locker. I get a great launch with a 5:42 gear with a wide ratio 4 speed Muncie. 14.3:1 in 1st gear. I paid $600 for it, and all the different gears are like $70 each. 8095

[55 Tony]

A good 10 inch 3500 convertor with your 342 gears would out preform yours with 4.11s.

Is that for a 1/8 mile or 1/4 mile or both?

[55 Tony]

Not knowing what tranny, 1st-2nd gear ratios, tire diameters, trap speed, etc. there is no way to give a good idea as to the best setup for your goal. If running an auto, a better plan is a 4 speed for sure, and run closer to the same size tire for track or street. Need to come up with a combo that gets the most out of 2nd gear I would think. Running a non-overdrive 1:1 trans will always be a compromise no matter how you slice it, unless you have a quick change rear, which I have. I can pick from like a 100 different ratios, that can be changed in 20 minutes. This is a 1974 Frankland with a 4:86 10 1/2 inch ring gear with a locker. I get a great launch with a 5:42 gear with a wide ratio 4 speed Muncie. 14.3:1 in 1st gear. I paid $600 for it, and all the different gears are like $70 each.

Can you run that on the street too? I never even heard of a Frankland before. I'm guessing that was a great price?

Oh, and back a little I said I have a TH400 and was looking at 28" slicks.

[markm]

Is that for a 1/8 mile or 1/4 mile or both?

When I gave up on the NHRA and started racing mostly 1/8 mile I built a 4.88 Dana Powerlock to replace my 4.10 in my 454 Camaro drag car. It screwed up my 60 foot time and 1/8 mile lost two tenths. Reinstalled 4.10 and life was good again. Car is equipped with a 8 inch Doherty bolt together convertor.

[Rick_L]

It's all in the combination. When you change one thing, you may have to change 2 or 3 more to get the results you want.

I will promise you that you could have made the car quicker with the 4.88 gears if you made other changes too. It's all in how much you want to beat on it, and how much $$ you're willing to spend to beat on it.

The Frankland is a dirt track quick change. Don't know much about it except that it exists. My last dragster had a Schiefer (later called a Richmond) quick change. We changed gears a lot, I guess part of that was because we could. They were never very common. I had S/N #2 and #6. Also had a bunch of magnesium castings for it to save weight, even had a reverser for the axle to use with a Lenco so that you wouldn't have to use a Lenco reverser with its added length. Looking back, while the ability to change gear ratios easily was a big plus, the inefficiency of the setup was a negative.

[55 Tony]

OK, Thanks everyone for all the info! I think I'm going to buy some slicks and see what it does and go from there. If we get a warm weekend, the track will be open even if it is winter. The way they are running things half assed is just fine for a rookie like me. To make things easier, I can put the slicks on at home and drive about 1.2 miles on back roads and be at the track. :)
I'm also going to start looking at the local pull-a-part for a 4L80E. No sense in buying a good converter if a tranny swap is in my future. I'll start a new thread about the 4L80E questions.

[55 Rescue Dog]

OK, Thanks everyone for all the info! I think I'm going to buy some slicks and see what it does and go from there. If we get a warm weekend, the track will be open even if it is winter. The way they are running things half assed is just fine for a rookie like me. To make things easier, I can put the slicks on at home and drive about 1.2 miles on back roads and be at the track. :)
I'm also going to start looking at the local pull-a-part for a 4L80E. No sense in buying a good converter if a tranny swap is in my future. I'll start a new thread about the 4L80E questions.
I would consider DOT drag radials that could be used on the street, and setup the suspension for better traction, along with the 4L80 using your current rear gear, and go from there.

[markm]

It's all in the combination. When you change one thing, you may have to change 2 or 3 more to get the results you want.

I will promise you that you could have made the car quicker with the 4.88 gears if you made other changes too. It's all in how much you want to beat on it, and how much $$ you're willing to spend to beat on it.

The Frankland is a dirt track quick change. Don't know much about it except that it exists. My last dragster had a Schiefer (later called a Richmond) quick change. We changed gears a lot, I guess part of that was because we could. They were never very common. I had S/N #2 and #6. Also had a bunch of magnesium castings for it to save weight, even had a reverser for the axle to use with a Lenco so that you wouldn't have to use a Lenco reverser with its added length. Looking back, while the ability to change gear ratios easily was a big plus, the inefficiency of the setup was a negative.

If I back halfed the car and installed a Powerglide and 14x32s, they probably would have worked. My 60 foot times went from mid to high 1.40s to 1.60s.

[55 Tony]

I would consider DOT drag radials that could be used on the street, and setup the suspension for better traction, along with the 4L80 using your current rear gear, and go from there.

I've talked to a few people that tried street slicks and they say they don't work very well. Or are you possibly saying (in a nice way) that with <500HP I wouldn't know the difference? I really don't know what my HP is. Right now on the ROAD, if I'm rolling at 20mph and go WOT they will spin pretty good then grab, then when it hits 2nd the speedometer jumps up 15 or 20 mph and down again. (I have the governor on the TH400 set to shift WOT @ 5500rpm) When it hits third at about 80mph, well I think it has chirped and/or felt is spin already but I wouldn't swear to it. It really bangs third hard.

[markm]

I tried BFG drag radials on my 67 Camaro, no better than my street tires, both 275/60/15s. 28x10.5 slicks now were talking.

[55 Tony]

I bought some Hoosiers that don't need tubes, I think they will arrive today. My poor UPS man, maybe he'll come early to get the tires out of the way. Maybe next week I'll get another set of wheels and some street tires. Merry Christmas to me. I really don't think I'll ever get like you guys concerned over a hundredth of a second, I just want a little fun for a medium amount of money. A little hobby, not a lifestyle. I hope anyway!

[markm]

1/10 on 60 ft time is huge on big end. The faster you go the more $$$ a couple tenths can cost.