rcknrolfender79

Hey guys I got a 1970 Roadrunner. Will post some pics this evening. It is originally a 383 4 speed dana 3.54 car. It has had the 383 replaced with a 71 440 out of a boat. The 440 has had lots of work done on it. Its had the intake, heads and exhaust port matched. The heads and block have all been milled for 0 tolerance.. The intake is a dual 4 bbl intake. It has 2 carter 4 barrels on it. Not sure what cfm. It's got a bigger cam in it... bottom line this car was meant to be a pretty serious 1/4 mile car. But something is odd.. And as long as I've been into cars and mopars some of my questions may come off stupid or noob like but I am very confused...

Ok the odd thing is that my Coronet R/T is also a 440 4 speed dana 3.54. So the gearing should feel the exact same. Well it doesnt. In the RR it is much higher geared. I would be in 4th in the r/t by time I hit second in the RR. Its kind of tough to get the RR to spin the tires even after all the work has been done on it. But my R/T you can look at the gas pedal and have it doing donuts. In the R/T I'm spinning about 2,500 rpms at 65 mph in 4th gear. In the RR it's probably at about 1700 to 2000 rpms. (dont have a tach in it to know for sure).

On the R/T the 440 is supposedly a stock motor out of a 68 police car. It has just had an aftermarket weiand intake holley 750 double pumper, headers, and some chrome bolted on. What could be different? I don't think the 4 speed in my car is the matching numbers 4 speed. But I do know it was a 440 4 speed dana car originally. Both the rear ends in the r/t and RR both have a 3.54 ratio tag. Both transmissions look to be a833 4 speeds. Haven't looked up the numbers on either one to check.. Did the a833 come with granny gears? Could it be possible that the R/T has a granny gear 4 speed? Or would be a better possibility that the RR has an overdrive 4 speed? I haven't driven an overdrive 4 speed before so i have no idea. Or would the chances be better that the R/T has had the 3.54 gears switched out with 3.91's or 4.10's? The RR has been setting in a shop for the last 13 years so I know the carbs aren't as clean as they should be and aren't tuned exactly right. You can tell its not running quite right. But there is an amazingly obvious difference in the gearing between the 2 cars. Any suggestions on what I should look at to possibly figure this out? Thanks guys

Moparod

Sounds like the Road Runner has an 833 overdrive transmission. They used them in the mid 70's and 80's. The R/T doesn't sound like it turning enough revs to be over a 3.54, my '68 Charger with a 3.91 Sure Grip would pull exactly 3000 revs @ 60, running P275/60/15 tires. Swapped out to a 2.76 for road trips and I could turn a tick under 2000 @ 80 mph.

http://www.motortopia.com/car-clubs/mopar-enthusiasts-car-club-of-america-194/car-forums/tech-talk-531/chrysler-a-833-four-speed-1244/page1

440roadrunner

Very very easy to check on the the 4 speed.

Just get under the car and look at the very front shift lever. If the front lever and the lever behind it are both pointing up, you have a conventional 1:1 4 speed

If the front shift lever is pointing DOWN you have an OD

This was a "trick" used by both Mopar and Ford. The OD is REALLY the "old" 3rd gear. Ma made new gearing so that 3rd gear is an OD gear. Then they simply turned the shift lever for 3rd/ 4th upside down.

This means that the shifter goes 1-2 as normal, but when you are in "3rd" you are ACTUALLY in the "old" 4th gear, the 1:1 gear. This also means that the "new third" is considerably stronger than the "new" 4th, OD gear.

Below is an OD, note the front shift lever



And so last, when you shift into "4th" with the shifter, you are mechanically putting the gearbox into the old 3rd gear position, now your OD gear.