3.55 rear gears

-
ir3333

ir3333

Well-Known Member
Joined
Jun 1, 2008
Messages
5,836
Reaction score
1,574
Location
ontario,canada
what is your rpm at highway speeds...say 60 or 70 mph and your tire size?
..does 2800 rpm @ 60 mph with a 26" tire sound about right?
 
Cruised to Carlisle over the weekend, 3.55's with a 245-60-15 tire (26.6") and it was right on 2.7 - 2.8k rpm at 60mph.
 
tx guys...my 3.23 front pinion seal is leaking badly and i have a rebuilt set of 3.55's on standby.
I like the 3.23 but have never tried 3.55's,i know i don't like 3.91
 
I had 3.55's in mine with 28" tall tires and it spun 2750~2800 rpm at 60 mph. At the moment I have 3.23's in it and it spins 2550~2600 at 60 mph. So many of the internet calculators are not accurate if you are running an automatic because all converters have a some slippage (unless it's a lock up converter). Here's a link to an interactive calculator that takes into account torque converter slippage which can be anywhere from 4-10% depending on how efficient the converter is.

http://vexer.com/automotive-tools/speed-rpm-calculator

BTW: I agree with Bob that 3.55's are a nice compromise in performance and drivability. I'm putting my 3.55's back in ASAP.
 
Man Fishy you must have a LOOSE converter.

Mine before I tore it down, 28.4 or less so tall tire, 3.7 gear, "tight" old "van" converter about a LOL 1800 stall, the thing ran somewheres 32-3300 at 70 mph

Calculator on mine with 28" tires shows about 2600 for 60mph. I would not want it any lower for the "street" but I'll tell you, even that little 318 snorted with that gearing.

2nc gear (manual body 727) was good for about 82 mph. So you could tap it down at 65 and 2nd was good for about 2 seconds and you were "back in third." I had the Holley rev limit at 5700 and it caught me off guard a couple of times.

It also caught the Richard I was passing off guard, LMAO
 
I knew a girl with a loose converter once. She revved pretty high.
 
67Dart273 said:
Man Fishy you must have a LOOSE converter.

Mine before I tore it down, 28.4 or less so tall tire, 3.7 gear, "tight" old "van" converter about a LOL 1800 stall, the thing ran somewheres 32-3300 at 70 mph

Calculator on mine with 28" tires shows about 2600 for 60mph. I would not want it any lower for the "street" but I'll tell you, even that little 318 snorted with that gearing.

2nc gear (manual body 727) was good for about 82 mph. So you could tap it down at 65 and 2nd was good for about 2 seconds and you were "back in third." I had the Holley rev limit at 5700 and it caught me off guard a couple of times.

It also caught the Richard I was passing off guard, LMAO
Click to expand...

It's a 3500 stall and it is an 11" model so it's not the most efficient. According to my figures it's slipping 8%. Generally speaking even a good 3500 stall will slip 6% so mine's not that bad, just somewhat bad, LOL... I've seen some cheap converters slip 10% or more.

What gear are you running Del? What calculator did you use to figure it? Like I mentioned above a lot of calculators don't take into account any converter slip at all so their figures are off when using them to figure rpm with an automatic. That's why I like the calculator I posted the link to. It has a way to switch it to automatic trans and dial in some converter slippage
 
ir3333 said:
what is your rpm at highway speeds...say 60 or 70 mph and your tire size?
..does 2800 rpm @ 60 mph with a 26" tire sound about right?
Click to expand...

My Challenger, same size tire and rear end ratio: Factory tach at 60 MPH is at just around 2800 rpm.
 
fishy68 said:
It's a 3500 stall and it is an 11" model so it's not the most efficient. According to my figures it's slipping 8%. Generally speaking even a good 3500 stall will slip 6% so mine's not that bad, just somewhat bad, LOL... I've seen some cheap converters slip 10% or more.

What gear are you running Del? What calculator did you use to figure it? Like I mentioned above a lot of calculators don't take into account any converter slip at all so their figures are off when using them to figure rpm with an automatic. That's why I like the calculator I posted the link to. It has a way to switch it to automatic trans and dial in some converter slippage
Click to expand...

The RPM at 70 is what I remember. Somewhere.........3200--3400. This is a Ford 9" 3.7, tires are just a touch over 28

http://www.forabodiesonly.com/mopar/showthread.php?t=237684

225 x 60 x 17 says they are 27 5/8

I was thinking of the old 15" I had on the car
 
You must log in or register to reply here.
-

Back
Top