Does this seem right?
Senior User
Joined: Nov 2014
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I just put it into a rpm calculator and 4.10's with 33's and a 1:1 ratio should be about 2100 rpm at 55.
But with the c6's second gear ratio being 1.55 I believe, if I put that into the calculator at 55 with the same specs as before it comes out to about 3500. So maybe you aren't shifting out of second?
Maybe the rear end was geared down but according to the calculator it would have to be like a 6.2 ratio or something.
Here's the calculator FYI
http://www.crawlpedia.com/rpm_gear_calculator.htm
But with the c6's second gear ratio being 1.55 I believe, if I put that into the calculator at 55 with the same specs as before it comes out to about 3500. So maybe you aren't shifting out of second?
Maybe the rear end was geared down but according to the calculator it would have to be like a 6.2 ratio or something.
Here's the calculator FYI
http://www.crawlpedia.com/rpm_gear_calculator.htm
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Tuned
Joined: Aug 2011
Posts: 282
Likes: 2
Thanks for that. That's sort of what I was thinking. I wonder how I can double-check the transmission? It's hard to hear or feel it shifting but maybe I can see it on the tach..... I also feel like maybe my diff is stuck in low.... It's a complete ******* to try and shift.
Senior User
Joined: Nov 2014
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Well gears tips multiply the torque so you should multiply the ratio to figure it out. If you have a 3:1 first gear with a 2:1 transfer case the you'd have the equivalent of a 6:1 gear ratio. So if you were in third and the transfer case was in low figure your transfer case low gear ratio and then use that in the trans gear ratio spot in the calculator. That would tell you what rpm having your t case in low would make you turn in any given situation
Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
I seriously doubt you could hit 50mph in low range. If you are running over sized tires you will actually be going faster than what your speedo is reading. So between that and the fact that the C6 transmission does not have a torque converter lock (there is always some slippage) I would say that is perfectly normal.
Edit. Just re read it and that does seem high. I would make sure it's shifting through all the gears. Good luck.
Edit. Just re read it and that does seem high. I would make sure it's shifting through all the gears. Good luck.
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Also if you want to check your tranny just floor it and count the times it shifts. Should have a 1-2 shift then a 2-3 shift.
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Been a few years since I had my 77 on the road (400/ C6/ 205/4.10) with LT305/70R16 (~33-34") but as I recall 3200 rpms put me pretty close to 75mph, verified with a GPS.
I'll bet it isn't shifting into 3rd. Easiest way to verify is to start out in 1st and shift it manually.
Robert
I'll bet it isn't shifting into 3rd. Easiest way to verify is to start out in 1st and shift it manually.
Robert
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