A B-body story.

[Cojohnso1]

I bought my 2nd GTX last year. To replace a loss from years ago. Although the cars are simular in appearance. With simular 440s. And same drive train. (4 speed with Dana rear 3.54:1) They perform very differently. My first was quicker thru the gears. This one is definitely faster on top end. My first started the speed vibration and was done at about 140. This one? Pegged speedo of 150 and that 440 was still pulling. Tach was saying 6k. (But that too is stock. And who knows its accuracy?) Confirmed by a Nissan GTR that I thought was supposed to be near 200 MPH car? (Although this one wasn't newest of models. And he may have lifted.) But be that as it may. The question: Are there higher gear sets for the Dana than 3.54:1? I never have heard of any like 3.23? Because something is different. I'm sure if I did the count drive shaft revs? It would be 3 1/2. Suggesting a 3.54:1. The rear tire is a little taller than front. But not that much to make this big of difference? But maybe? What does one inch tire height mean in MPH? (I'm sure there is a calculator out there.)

 

[PurpleBeeper]

3.54 is the "most highway" gear for a Dana that I'm aware of, at least for factory Mopar Dana's. Yes, there are speed calculators online in several places that will allow you to calculate speed vs. tire size.

If you're a math guy..... C = (pi)D and the speed difference "in theory" would be C2/C1 * top speed.

Be aware that with most GTX's you're basically shoving a brick through the air (not very aerodynamic). You are already above what I would consider a "safe speed" for your suspension at 150mph & WAY past your tire rating of 112mph or 118mph (assuming you have 15" wheels). A tire blow out at 150mph is very hard to survive....just sayin'

 

[yella71]

Yes dad we know he was going faster than he should have been..... But to answer your question the first gen dodge cummins pick ups only had a 3 spd trans so they put a 3.07 ratio in the dana 60....it takes a special carrier and gears. im not sure how easy they are to find but the posi carrier may be like hens teeth. My truck is an open rear. It really could use a posi rear... Yeah I said posi

 

[Cojohnso1]

Yeah. No kidding. My first GTX would move around and begin it's vibration well before. This guy sits different. And felt much more in control. But is slower thru the gears. Like it's a different model car. I was told of high speed stories from the guy I purchased. I blew it off until I felt it. This time the tales were true. But nobody needs to go that fast. I would trade for 4:10s and be a little snappier.

 

[Jerry Hall]

They weren't safe then or now, but I will take today's tire technology over then. My only problem today is finding a place to put them through their paces. My first objective in the day was to find out how fast it was and what it was going to take to make it faster. I have been well over 150 back in the late 60's on 40 bucks worth of used tires, but would I do it today?? Probably not, the safer environment is not there and I value life a lot more. That said, I have had my 96 Viper Coupe to 175 on the track in Savannah, GA. and a little more than that at a track day in Talladega. Both places I was the only one in danger. If I drive like that today, I would certainly try to be sure I'm the only one in danger.
As far as the difference in the two GTX's is concerned, every car is different you just have to find those differences.

 

[dadsbee]

If you're worried about tires giving up on you then you'd better park that car and grab a blanket PB ! Here's my car when I grabbed it from my Mother's after Dad died in 1986. Those old CTC Tornado bias ply tires saw 150+ on MANY a Friday night in the early '80's with my 4 gear and 2.94's.. pedal mashed to the floor for MILES.

That said, I believe you could get a Dana with 3.23's, at least in '68.

 

[Jerry Hall]

That said, I believe you could get a Dana with 3.23's, at least in '68.

Not sure about a 3:23 Dana in 68, but a while back there was a member from Mexico talking about a Dana with 3:32 gears in a 68 Coronet.

 

[Ranger16]

What does one inch tire height mean in MPH? (I'm sure there is a calculator out there.)

Here's one of many.
http://www.advanced-ev.com/Calculators/TireSize/

 

[Cojohnso1]

I know in the 8 3/4. And I know you can't get any performance gears like Strange for higher than 3.54. Plenty for deeper gear sets. I have changed gears in 8 3/4 as well as Ford 9". But Dana's? They're different with the shims and alignment. I know. "About time you learned." But it's tough to remove and replace perfectly performing parts. Just because you wish for a small performance change.

 

[Cojohnso1]

Ok. My inquiry got me curious so I went out to the garage and checked tires. What I didn't notice was the rears are 15" rims. (I don't know how I missed that?) So tire profile is about 2" taller. And rear of car definitely sitting higher than stock. That certainly explains RPM difference. So now I have 2 more questions for the old owner. How did he get different size rims of same age? And why? This would also change dynamics of car. Personally I wouldn't have spent money just to see if it improved. But I have to say? I believe it does cut thru the air better. I wonder if that's true for A-body? My Duster bracket car runs 15s on both front and rear. Never occured to me to try 14s up front? Just posting observations. I have no mechanical evidence to support. In fact, I would think it would bind a bit on the geometry. But no evidence or observation of that either. That should cause more higher speed vibration. Not less. (although there is a number of factors that can cause vibration. Front end, wheel bearing performance, axle and bearing performance, transmission, rear gear age and balance, driveshaft.) But different tires and rims didn't seem to change in car #1. Car #2 just might be better balanced at speed?

 

[mopar 3 B]

What size of 15" tires? They would have to be pretty tall to do 150 mph at 6000 rpm with 3.54 gears.

 

[WileERobby]

Factory was 3.54 track pack, 4.10 super track pack.

 

[33 IMP]

Andy F posted a while back that he was testing some 3.23 dana gears for Dr. Diff. I haven't heard the results.

 

[Cojohnso1]

What size of 15" tires? They would have to be pretty tall to do 150 mph at 6000 rpm with 3.54 gears.

P275 60. 28" calculator suggests about 6300 RPM for 150 MPH with 3.54:1 gear. That might be about right. I'm guessing speedo or tach is not 100%. I of course only had the time to glance at them. Was chewing up alot of real estate.

 

[PurpleBeeper]

If you're worried about tires giving up on you then you'd better park that car and grab a blanket PB ! Here's my car when I grabbed it from my Mother's after Dad died in 1986. Those old CTC Tornado bias ply tires saw 150+ on MANY a Friday night in the early '80's with my 4 gear and 2.94's.. pedal mashed to the floor for MILES.

That said, I believe you could get a Dana with 3.23's, at least in '68.

View attachment 735060

Honestly, I have been WAY over 150mph before I ever hit the nitrous button...on old-school 112mph tires (yeah, I'm stupid too). For me, step #1 is getting some V-rated or better tires. Step #2 lower the car 3"-4". Step #3 do what you can to minimize air under the car, and if possible reduce the front end wind resistance (lower drag coefficent). Step #4 start playing with rear end gear ratios.

FYI- Years ago I looked in building a 200+mph street car. Behind the winged cars, the '71-'74 Dodge Chargers have the lowest drag coefficient. Air underneath the car is very bad at high speed, so some type of chin spoiler (look at NASCAR) would be very helpful. In b-bodies, I've found that they start to get squirrely at right about 140-150mph & then you start drifting about a 1/2 lane every little bump in the road.

 

[dadsbee]

LOL PB... all I know is my buddy never wanted to count hydro poles and usually had has hands wrapped around the bottom of the seat.... and we NEVER spilled our beers so the drifting couldn't have been too bad!

 

[Jerry Hall]

FYI- Years ago I looked in building a 200+mph street car. Behind the winged cars, the '71-'74 Dodge Chargers have the lowest drag coefficient. Air underneath the car is very bad at high speed, so some type of chin spoiler (look at NASCAR) would be very helpful. In b-bodies, I've found that they start to get squirrely at right about 140-150mph & then you start drifting about a 1/2 lane every little bump in the road

It's not just the old cars. My 96 Viper GTS Coupe is very touchy, light, and the steering is over sensitive at 160 +. A slight turn at 170, which would look like a straight road at 70, looks like the 4th turn at Daytona. A kid at a car show asked how fast will it go. My answer was I don't know. He said that would be the first thing he would find out if it were his. I related the 170mph experience and told him "that car has more balls than I do". Even though I have been on quite a few high speed road courses, the 170-200 mph speeds are not for me. I'll play with you all day long up to a little over 160, but more than that I'll just stay home.