2000 RPM @ 65 mph, 700R4, 245/50/16 tires, and 2.73 gear
#1
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
2000 RPM @ 65 mph, 700R4, 245/50/16 tires, and 2.73 gear
Cruising down the highway, this is the situation. I've verified the RPMs via a computer, and verified the rear gear by popping the cover and counting teeth. I'm about to go test my TCC lockup, but I'm fairly certain its working. What could this be? Can a transmission be constantly slipping on a high speed, low PRM condition cruise condition?
#2
Joined: Aug 2006
Posts: 12,667
Likes: 50
From: Central NJ
Car: 86 Trans Am, 92 Firebird
Engine: 408 sbc, 3.1L of raw power
Transmission: TKO600, T5
Axle/Gears: Moser 9", 3:70 trutac, 3:23 torsion
i would definatly say there is something wrong. i used to have the same setup and i would at times be around 1000 RPMs at that speed.
#3
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Joined: Jul 1999
Posts: 10,907
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From: The Bone Yard
Car: Death Mobile
Engine: 666 c.i.
Sounds like your TCC isn't locking up.
It may be a variety of reasons for your TCC not locking. List includes: it's not wired, broken connection, eprom set too high/disabled or TCC is either not working or non-locking type.
It may be a variety of reasons for your TCC not locking. List includes: it's not wired, broken connection, eprom set too high/disabled or TCC is either not working or non-locking type.
#4
Joined: Feb 2007
Posts: 4,657
Likes: 57
From: northern New Jersey
Car: 87 TA clone
Engine: 70/70 Turbo 5.3 LS
Transmission: bullet proof 2004R
Axle/Gears: ford 8.8, 3.55 gears
i have the stock 3.23's with my 700r4 and im at roughly 2000 rpms at 60/65mph. your 2.73's like my 86 should be alot lower prob like 1500
#7
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Well just went out and tested my TCC. It's locking up fine. Tapped the brake at 65mph and the RPMs went up a bit for a second then went back down. Still turning ~1900-2000 RPM though at this speed. By these calculations I should have a 3.23 rear. However I counted the teeth and got 41:15 which means 2.73. What could possibly be happening??
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#8
Well just went out and tested my TCC. It's locking up fine. Tapped the brake at 65mph and the RPMs went up a bit for a second then went back down. Still turning ~1900-2000 RPM though at this speed. By these calculations I should have a 3.23 rear. However I counted the teeth and got 41:15 which means 2.73. What could possibly be happening??
#9
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
I'm not using my stock tach, I'm using my laptop which is plugged directly into my ECM. How do you figure that anyway?
With a 245/50/16 tire, 2.73 gears, and a .7:1 overdrive I should be doing 80mph @ 2000 rpm, NOT 65. Something is not right. My car is acting like it has a ~3.23 rear gear when it certainly does not.
With a 245/50/16 tire, 2.73 gears, and a .7:1 overdrive I should be doing 80mph @ 2000 rpm, NOT 65. Something is not right. My car is acting like it has a ~3.23 rear gear when it certainly does not.
#10
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Joined: Sep 2005
Posts: 1,951
Likes: 7
From: Ottawa, ONT
Car: 1987 Firebird
Engine: 355
Transmission: T56
Darkshot, i dont have solution or a theory yet, but i think some more information would help. How is your lockup designed? Is it factory, or custom? ie: only designed to come on in overdrive? And how is the car behaving in other gears. ie: if you are cruising in second or third, what sort of RPMS and speeds are you getting? Might help track down the prob. Maybe clutch pack probs, or probs with a gear? Or maybe torque converter is worn?
#12
I'm not using my stock tach, I'm using my laptop which is plugged directly into my ECM. How do you figure that anyway?
With a 245/50/16 tire, 2.73 gears, and a .7:1 overdrive I should be doing 80mph @ 2000 rpm, NOT 65. Something is not right. My car is acting like it has a ~3.23 rear gear when it certainly does not.
With a 245/50/16 tire, 2.73 gears, and a .7:1 overdrive I should be doing 80mph @ 2000 rpm, NOT 65. Something is not right. My car is acting like it has a ~3.23 rear gear when it certainly does not.
about as close as you can get. Do the math yourself or plug in the data and let the formula calulate it. Your numbers are incorrect in my opinion and it looks like everything is find. Another quick check is drive in OD at steady 40 MPH and your tach should read 1000 rpms.
Last edited by DJP87Z28; 03-05-2007 at 08:49 AM.
#13
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Joined: Oct 2006
Posts: 250
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From: ludlow mass
Car: 02 Mustang
Engine: 3.8 about to be punched out to 4.3
Transmission: 4R70W
Axle/Gears: 3.73 Detroit true trac
sounds like your not in overdrive and in 3rd, i have 3.73s and am at 2000 rpms in OD with 215-65-15s on
#14
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From: Winnipeg Manitoba Canada
Car: 92 trans am/ 93 dodge spirit V6
Engine: L98 V8 - 350
Transmission: TH-700-R4
Axle/Gears: 3.23
man, 92 ta, 700r4 and 3.23's im at 1800 at 60 mph, and 2000 at 70 mph. could be the tach being off, but thats what i get.
#15
Joined: Feb 2007
Posts: 4,657
Likes: 57
From: northern New Jersey
Car: 87 TA clone
Engine: 70/70 Turbo 5.3 LS
Transmission: bullet proof 2004R
Axle/Gears: ford 8.8, 3.55 gears
in 3rd with 3.23 im running 2000 at 40mph roughly. i checked my tach through the comp and a code reader and my tach is dead on and so is my speedo. as i said before with 2.73 like my 86 tpi with 700r4 u should be running around 1500. u should not be near 2000 at 60/65 with 2.73's. how is ur trans shifting? does it shift good no lag etc, or is it slow into gear and when u step on the pass does ur RPM's rise but the car doesnt accellerate? if thats whats happening its ur trans plates are slipping, or torque converter,if not it could be the converter,speedo gears, maybe even ur rear is goin....
#16
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
My TCC setup is stock, AFAIK. I'm riding around with a laptop on my passenger seat connected to my ECM running WhatsUp software, which has a TCC lockup indicator. It locks up at 33 mph (in 3rd) as I set in the PROM. My trans shifts into OD at 40. TCC stays locked through the shift and all the way up through 60mph, 70mph, etc. Wont unlock unless I tap the brake, or put my foot in it. At 65 mph I can tap the brake, and my RPMs will jump up slightly while the TCC unlocks. The TCC indicator on my laptop also shuts off when I do this, and comes back on then the RPMs go back down (This is how I varify the reliability of the TCC indicator on my laptop). I have varified my guages, both MPH and RPM, with the computer. They are accurate throughout the range and are NOT the problem.
Like I said, AFAIK, this is stock behavior. However the engine is still spinning many PRM higher than it should be. My transmission is known to have problems. It slips sometimes in first gear, always slips on kickdown to 2nd gear, it clunks, whines, and bangs, all internally (no broken external mounts or anything). My original question is can a transmission *constantly and consistantly* slip like this? I just always think of transmission slipping as random and erratic, not eating up 'x' RPMS as some function of vehicle speed.
Like I said, AFAIK, this is stock behavior. However the engine is still spinning many PRM higher than it should be. My transmission is known to have problems. It slips sometimes in first gear, always slips on kickdown to 2nd gear, it clunks, whines, and bangs, all internally (no broken external mounts or anything). My original question is can a transmission *constantly and consistantly* slip like this? I just always think of transmission slipping as random and erratic, not eating up 'x' RPMS as some function of vehicle speed.
Can a transmission be constantly slipping on a high speed, low PRM condition cruise condition?
#17
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From: Weedsport, NY
Car: 1986 Camaro SC
Engine: Bolt-on/cam 305
Transmission: 700R4 w/ 2500stall
Axle/Gears: 3.73 10bolt Posi
My TCC setup is stock, AFAIK. I'm riding around with a laptop on my passenger seat connected to my ECM running WhatsUp software, which has a TCC lockup indicator. It locks up at 33 mph (in 3rd) as I set in the PROM. My trans shifts into OD at 40. TCC stays locked through the shift and all the way up through 60mph, 70mph, etc. Wont unlock unless I tap the brake, or put my foot in it. At 65 mph I can tap the brake, and my RPMs will jump up slightly while the TCC unlocks. The TCC indicator on my laptop also shuts off when I do this, and comes back on then the RPMs go back down (This is how I varify the reliability of the TCC indicator on my laptop). I have varified my guages, both MPH and RPM, with the computer. They are accurate throughout the range and are NOT the problem.
Like I said, AFAIK, this is stock behavior. However the engine is still spinning many PRM higher than it should be. My transmission is known to have problems. It slips sometimes in first gear, always slips on kickdown to 2nd gear, it clunks, whines, and bangs, all internally (no broken external mounts or anything). My original question is can a transmission *constantly and consistantly* slip like this? I just always think of transmission slipping as random and erratic, not eating up 'x' RPMS as some function of vehicle speed.
Like I said, AFAIK, this is stock behavior. However the engine is still spinning many PRM higher than it should be. My transmission is known to have problems. It slips sometimes in first gear, always slips on kickdown to 2nd gear, it clunks, whines, and bangs, all internally (no broken external mounts or anything). My original question is can a transmission *constantly and consistantly* slip like this? I just always think of transmission slipping as random and erratic, not eating up 'x' RPMS as some function of vehicle speed.
#18
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Well I only realized the RPM inconsistencies since I fixed my tach and started cruising around with a somewhat accurate tach. At first I thought my re-calibration of the tach was off, but when I connected the computer to it my guage I saw that it is very close. Accurate enough that at 2000 RPMs the needle is about one needle's worth of width below 2000. (does this make sense?) This means I only know for sure that its been happening for a month or so, but I have no reason to believe it hasn't been doing this since I got it a year ago. It gets about 30 highway miles (in 5 mile spurts between which it cools off), plus about 75 city miles each week.
This slipping and drag would account for my gas mileage problem which I have NOT been able to track down. The best I can reliably manage over time with the above distribution of miles is 12mpg. The best i've seen was one tank of 17mpg, which was surprisingly all city. Maybe things are finally coming together.
This slipping and drag would account for my gas mileage problem which I have NOT been able to track down. The best I can reliably manage over time with the above distribution of miles is 12mpg. The best i've seen was one tank of 17mpg, which was surprisingly all city. Maybe things are finally coming together.
Last edited by Darkshot; 03-06-2007 at 04:52 AM.
#19
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Re: 2000 RPM @ 65 mph, 700R4, 245/50/16 tires, and 2.73 gear
Problem solved. I just went out and drove on the highway alongside my friend's mom's 06 Camry....my 55 is the same as its 65.
#20
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From: Weedsport, NY
Car: 1986 Camaro SC
Engine: Bolt-on/cam 305
Transmission: 700R4 w/ 2500stall
Axle/Gears: 3.73 10bolt Posi
Re: 2000 RPM @ 65 mph, 700R4, 245/50/16 tires, and 2.73 gear
Gauges will do it every time. Whats the fix for the speedometer - wrong gear in the tranny? Either way, it beats the possible alternatives you were facing.
#21
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From: Sacramento
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Re: 2000 RPM @ 65 mph, 700R4, 245/50/16 tires, and 2.73 gear
What worries me is my ECM readout matches my guage, so the computer thinks I'm going faster than I am. Anybody know how to fix this?
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