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#1064147 - 11/14/19 05:03 PM High Cruising RPM  
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jmireles Offline
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jmireles  Offline
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El Paso, Tx
So I feel the engine in my Monte is turning over too quickly for the speed I'm cruising at. So let's say I'm driving at 70 MPH, the RPM gauge reads around 3K. I have a completely stock LS2/4L65e out of an '06 GTO and a 9" with 3.70 gears. It has a .69:1 overdrive gear. I double checked the RPM gauge by connecting a scanner and it is within 100 RPM of the gauge. Does that sound right??

I have a '77 Trans Am with a Pontiac 467/TH400 with 3.23 gears that will show around 2.5K on the RPM gauge at the same speed. The turbo 400 has a 3rd gear with 1:1.

Any insight is appreciated.


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1064148 - 11/14/19 05:31 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Apr 2011
Posts: 1,022
Hunter79764 Offline
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Hunter79764  Offline
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Posts: 1,022
Grand Prairie, Tx
What's the tire size?


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1064149 - 11/14/19 05:57 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Nov 2008
Posts: 622
jmireles Offline
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jmireles  Offline
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Posts: 622
El Paso, Tx
Yeah, I forgot that.

Monte has 215/60-15
Trans Am has 245/60-15

I think they both have a 27in. tall tire.


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1064150 - 11/14/19 06:00 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Nov 2008
Posts: 622
jmireles Offline
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jmireles  Offline
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Posts: 622
El Paso, Tx
I was off by a bit...25 in. tires.


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1064151 - 11/14/19 06:04 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Jan 2000
Posts: 4,772
mmc427ss Online content
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mmc427ss  Online Content
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Posts: 4,772
Pottstown, Pa
Very good calculator to check the numbers.

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php
Bob

#1064153 - 11/14/19 07:11 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Apr 2011
Posts: 1,022
Hunter79764 Offline
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Hunter79764  Offline
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Posts: 1,022
Grand Prairie, Tx
Seems like you should be closer to 2500 @70 in OD, and if it wasn't going into 4th but rather staying in 3rd, it should be around 3500. Do you have a loose converter that might not be locking up? I'd expect a couple hundred RPM rise with no lockup engaged, maybe more if it has some stall to it...


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1064158 - 11/15/19 04:40 AM Re: High Cruising RPM [Re: jmireles]  
Joined: May 2000
Posts: 1,685
BadSS Offline
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BadSS  Offline
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Pearl, MS, 39208
It's been a long time since I ran a lock-up transmission in the Monte and have never run a 4l65e. Best I remember the rpm difference between being locked and unlocked was around 100 maybe 150 rpm (???) increase/decrease, Tomorrow if I can remember I'll check to see what the difference is in the 6L80e in the G8.

However, I did have a friend with a 4l65e that was slipping about 800 rpm in high gear when his torque converter clutch wasn't engaging and the tran temps increased significantly. When you drive it again, get up to about 60mph keep your foot at the same position on the throttle and use your left foot to barely press the brake pedal to check to see if there is a change in RPM. If not your lockup isn't engaging and could be increasing the temp high enough to get a good bit of slippage. Best I remember my buddy had a wiring issue and a fluid pressure issue causing his excessive increase in RPM/slippage problem.

Hope that helps in some way.

#1064162 - 11/15/19 02:03 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Mar 2000
Posts: 5,540
upflying Offline
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upflying  Offline
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Reno, NV
I'm at 2500 rpm at 70 mph.
I am using this to control my 4L65E.
https://www.gmperformancemotor.com/parts/19302405.html


86 MCSS Notchback coupe, LS3, 4L65E, QP 9", Eaton Truetrac, 4 wheel disc, column shift, Dakota Digital, silver with maroon bench interior

#1064171 - 11/16/19 06:21 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Nov 2008
Posts: 622
jmireles Offline
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jmireles  Offline
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Joined: Nov 2008
Posts: 622
El Paso, Tx
Upflying,

Didn’t you LS swap your Monte too? Why do you need a controller for the transmission if the PCM is running things?


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1064173 - 11/16/19 08:24 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Mar 2000
Posts: 5,540
upflying Offline
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upflying  Offline
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Joined: Mar 2000
Posts: 5,540
Reno, NV
Originally Posted by jmireles
Upflying,

Didn’t you LS swap your Monte too? Why do you need a controller for the transmission if the PCM is running things?

Good question, my LS3/4L65E swap is a Connect and Cruise from GM Performance..it included the trans controller and the PCM as a complete plug and play package. The installation instructions were detailed and required the installation of the controller. I wasn't aware the PCM could control the transmission without the trans controller..
This is what I purchased and installed, you can see the trans controller in the photo.
https://www.chevrolet.com/performance/connect-cruise-powertrain-systems

Last edited by upflying; 11/16/19 08:26 PM.

86 MCSS Notchback coupe, LS3, 4L65E, QP 9", Eaton Truetrac, 4 wheel disc, column shift, Dakota Digital, silver with maroon bench interior

#1064177 - 11/18/19 05:52 AM Re: High Cruising RPM [Re: BadSS]  
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Posts: 622
jmireles Offline
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jmireles  Offline
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Joined: Nov 2008
Posts: 622
El Paso, Tx

Originally Posted by BadSS

When you drive it again, get up to about 60mph keep your foot at the same position on the throttle and use your left foot to barely press the brake pedal to check to see if there is a change in RPM.


I finally had some time to drive the Monte around today and performed this test. The RPM did slightly change...it rose about 200 or so RPM. So I guess the converter is locking up?


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1064178 - 11/18/19 02:04 PM Re: High Cruising RPM [Re: jmireles]  
Joined: Apr 2011
Posts: 1,022
Hunter79764 Offline
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Hunter79764  Offline
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Joined: Apr 2011
Posts: 1,022
Grand Prairie, Tx
Sounds like it is working, so it rules that out.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1064183 - 11/19/19 12:31 AM Re: High Cruising RPM [Re: jmireles]  
Joined: May 2019
Posts: 145
T5montecarlo Offline
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T5montecarlo  Offline
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Posts: 145
Lederach, PA
But if the converter was locked, there would be no change in rpm if the speed did not change.

At 70 mph, he is turning 2500 rpm. At 60 mph, he would be turning 2142 rpm ((60x2500)/70). An increase of 200 rpm increase would be approximately an increase of 5.6 mph if the converter is locked up. If the car speed did not increase by 5-6 mph, the converter is not locking up.

Marc

#1064184 - 11/19/19 12:42 AM Re: High Cruising RPM [Re: jmireles]  
Joined: Jan 2000
Posts: 4,772
mmc427ss Online content
20+ Year
mmc427ss  Online Content
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Posts: 4,772
Pottstown, Pa
Oh, you stick shift guys. Locking or unlocking the converter makes no difference in mph. The rpm only changes because the converter is slipping when unlocked. Same thing as slipping the clutch at 60 a little bit,
Bob

#1064185 - 11/19/19 01:22 AM Re: High Cruising RPM [Re: jmireles]  
Joined: May 2019
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T5montecarlo Offline
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T5montecarlo  Offline
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Posts: 145
Lederach, PA
OK, brain fart occurred. When pressing the brake, the converter will unlock, so a failed test. The same test should be tried without pressing on the brake. If the rpm flare, the converter is not locked.

Marc

Last edited by T5montecarlo; 11/19/19 01:22 AM.

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