Cruisin with low gears ?

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draginmopars

draginmopars

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Plan on making a few cruises this year.
they include a 60 + mile road trip from the meeting place to a Drag strip.
My Dart has 3.73 gear and a 518.
325-50 tires
1410 u joints

another project i'm working on
has a a500 trans, 275 -60 tires
gears not chosen yet.

The question is would 4.56 gears be to low.
OD would be like 3.15

I'm wondering about driveshaft speed @ 70 mph, heat
 
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both are overdrives and if in overdrive it would be like 3.15 that is awesome.....just about right for cruising
 
4.56 is not low enough? Hope this is in a spool rear end?
 
I ran 4.30s for a couple of years, with 27" tires, and a M/T. I live 20 minutes from the nearest town, so all my driving always includes at least that, twice.
I later sold the 4.30s looking perfect.

Getting the D/S balanced took two tries. There is still some vibration somewhere back there, that I was never able to eradicate. Just enough to be noticed.
 
I ran 4.56 with 295/50/15 tires and a 4-speed. 3500 rpm at 60. Perfect! People used to pull alongside me and tell me to shift. LOL.
 
@draginmopars

Final gear ratio will have to work with the cam and the converter. If it is to offset, an additional trans cooler should be added on. I don’t care what the way for cooling capacity, bigger the cooler, the better.
 
have 2 trans coolers in the dart

SAM_5004.JPG
 
Drove 140 miles round trip to Spring fling on 3.91's and 205/70R14's. 340 seemed to be right in its sweet spot at about 65, no problems...and instant throttle response.
 
Your worries are valid.... but tell us more!
how loose is the converter? Or is it a lock up? Is it a stock driveshaft or something else?

I have a 200r4 lock up 3200ish stall, 4:10’s. If I don’t lock the converter and cruise in 4th too far below the stall rating for a bit I build quite a bit of heat. I actually plan to relocate my plate cooler off the radiator this winter... if I am locked up, or cruise at a more efficient rpm for the converter it’s a non issue. In my head the lock up is well worth it, it’s literlaly like 5th gear.

As far as driveshaft speed your RPM of the shaft should be whatever the engine RPM would be in 3rd with a given gear-set. I wouldn’t think 4:56 at 70 would be too crazy... If it’s got fresh U-joints and been balanced that will help for sure. However, I’d calla driveline shop to get their opinion as I know shaft material, length and diameter can effect their safe RPM. I wouldn’t mind buzzing past their suggested RPM from time to time but a long cruise might spell trouble.

Joe
 
joeboy said:
Your worries are valid.... but tell us more!
how loose is the converter? Or is it a lock up? Is it a stock driveshaft or something else?
Joe
Click to expand...
The engine is out of my satellite, de-tuned it for the street.
The Trans is out of my Car hauler, converter built for the Dart, is a lock-up,
Driveshaft was built with new tube and 1410 ends
Dart is 3.73 gears.

The other project is in the planning stages> what parts to use >
A-500, have many 4.56 gear sets
haven't decided on which small block

026.JPG
 
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The dart with 3.73’s should be zero issues... sounds like you’re on the right track.

The 4.56 with that tire would turn like 3950 driveshaft RPM at 70. That really close to my dart with 4.10 and a much shorter tire. math on mine at 70 is 3800, ive had zero issues cruising 75-80 for 30-50 mile stints... so you should be good assuming it’s also a good drive shaft, especially in a shorter length for a a-body.

As far as heat goes with the 4.56, with the OD gear would be roughly 2700 RPM at the engine side. So you’d need a lock up converter or a stall speed less than that to keep it cool for long hauls. (Or a big *** cooler of course)

Joe
 
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