4.56 Question and Winter Pics
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Record Breaker
Joined: Oct 2008
Posts: 1,158
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From: Edmonton Ab Canada
4.56 Question and Winter Pics
Hello everyone. I just picked up a trailer for my sled and now I have come to realise how terrible 3.73's and 35's are when towing even a tiny trailer with some wind. I really wanna do 4.56's but before I leap I would like to know what rpm the truck will turn going down the highway with 35 inch tires. Right now im at 60mph and turning 1500 rpm. 80 mph nets me 2000 rpm some feed back would be great as to what rpm change would occur as a gear change result. And now for the entertainment here are some pictars. Forgive my dirty truck the roads here are so sloppy.
Record Breaker
Joined: Oct 2005
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From: Las Vegas
http://www.car-videos.net/tools/speedrpm.asp
will that help? there is a formula for calculating rpm, but i cant find it right now.
will that help? there is a formula for calculating rpm, but i cant find it right now.
Administrator
Joined: Jul 2007
Posts: 24,686
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From: South Georgia/East Florida
Going from 3.92s to 4.56s I turn about 400 more RPM at about 70 mph if that gives you some indication. So going from 3.73s to 4.56s I'd say about 500 rpm at that speed.
Yeah, that 2nd OD really is a killer for power. Your RPMs are way too low! The Hemi has a "sweet spot" between 2000 and about 2300 RPM where it's perfectly balanced for power and fuel economy. You really want to regear so you are cruising in that range. 4.56s will REALLY wake that truck up, performance wise and don't be shocked if your over-all fuel economy goes up by 1-2 mpg also...
Yeah, that 2nd OD really is a killer for power. Your RPMs are way too low! The Hemi has a "sweet spot" between 2000 and about 2300 RPM where it's perfectly balanced for power and fuel economy. You really want to regear so you are cruising in that range. 4.56s will REALLY wake that truck up, performance wise and don't be shocked if your over-all fuel economy goes up by 1-2 mpg also...
Grand Champion
Joined: May 2006
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From: Gilbert, Arizona
+1 on Hammer's post. At 65mph (freeway speed limit) I went from 1600rpm to around 2100rpm. At 75mph Im sitting comfortably between 2300-2500rpms. Not sure how the rpms will go up while pulling a trailer though.
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Record Breaker
Joined: Oct 2008
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From: Edmonton Ab Canada
Its a 02 Summit 800X
And yeah this should be a real nice up grade and I get the gears at wholesale price so 450 for both sets of gears and I can do the install at the shop so yeah this will be a welcome upgrade. Im super pumped no more pulling the trailer with overdrive off.
And yeah this should be a real nice up grade and I get the gears at wholesale price so 450 for both sets of gears and I can do the install at the shop so yeah this will be a welcome upgrade. Im super pumped no more pulling the trailer with overdrive off.
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Captain
Joined: Dec 2008
Posts: 712
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From: washington
Redone4x4, that calculator is nice, with a little digging I found this back in the archives and had some fun playing with it.
5-45RFE:
1st - 3.00:1
2nd - 1.67:1 (upshift)
2nd - 1.50:1 (downshift)
3rd - 1.00:1
4th - 0.75:1
5th - 0.67:1
Found it here; https://dodgeforum.com/forum/dodge-r...e-5-45rfe.html
5-45RFE:
1st - 3.00:1
2nd - 1.67:1 (upshift)
2nd - 1.50:1 (downshift)
3rd - 1.00:1
4th - 0.75:1
5th - 0.67:1
Found it here; https://dodgeforum.com/forum/dodge-r...e-5-45rfe.html
