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Old 08-08-2019, 04:26 PM   #1
Silverblu02SL2
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2002 SL2
Default Any tests to determine if my MP7 transmission is slipping or not ?

I am not used to driving automatics. My daily driver is a 5 spd manual diesel.

I think, but not sure, if my 2002 SL2 with the MP7 automatic tranny is slipping or not. It just does not accelerate the way I think it should if I apply throttle, especially compared to a 2012 Honda Accord I drove recently.

Any good tests to determine if my MP7 is slipping or not?

Does it have lock-up on all gears or only in top gear?

I found these gear ratios in a wiki for 1998-2002 MP7. are they accurate?

1st 2.530
2nd 1.560
3rd 1.030
4th 0.700
final 4.063
...
1/28/2019 2002 SL2 w 62k miles
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Old 08-08-2019, 06:56 PM   #2
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

If there is excessiv4 slip the TCU will set all kinds of codes and you will notice. Locks up in al gears.
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Old 08-11-2019, 08:00 AM   #3
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Maybe the torque converter is not transferring the power correctly, anything else would show up as a code as the PCM, Engine, and Transaxle all need to work together. PCM monitors engine RPM and the speed sensor in the transaxle to determine shift points, if any of those were faulty, you get codes and your SES light comes on. Remember these cars only have 124 HP and a measly 122 ft pounds of torque. That is not much today. Considering the last one was made 17 years ago, the HP and Torque ratings would not even be today as it left the factory unless you got an extremely well cared for one with low mileage. I remember when we sold the wife's 1984 2.3L Mustang and took delivery of our brand new 2000 SL2, it seemed to have gobs of more power that the Mustang. Now when I drive my daughters 2017 Turbo Cruze with 152 HP, the old Saturn seems really slow. Perception. ? The Accord must have at least 50 more horsepower and definitely much more torque. Not a fair comparison in my opinion. 122 ft pounds of torque is not much in todays standards
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Old 08-11-2019, 08:36 AM   #4
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

The VSS and TSS are indeed monitoring the input and output of the torque converter and this is wat sets all the slip codes. The torque converter function is monitored.
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Old 08-11-2019, 08:39 PM   #5
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

If you have slipping clutches, the input turbine sensor will set a DTC and the PCM will lockout that gear. The code will scan as "No xx gear/Incorrect ratio".

With OBD-II, it will be P0731-P0734 codes for slipping clutch packs.

No tests, other than pulling the valve body and performing air tests on the clutch packs.

Lockup should occur between 18-25 mph in 2nd gear, and 3rd/4th should also lockup. The TCC only locks in 1st gear when the PCM detects WOT.
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Old 08-11-2019, 10:46 PM   #6
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

I don't believe the final torque converter drive lockup ratio is 4.063 as stated.
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Old 08-12-2019, 09:06 AM   #7
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by toggenburg View Post
I don't believe the final torque converter drive lockup ratio is 4.063 as stated.
I got it from https://en.wikipedia.org/wiki/Saturn_MP_transmission

Can you provide the correct value from a reliable source?
...
1/28/2019 2002 SL2 w 62k miles
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Old 08-12-2019, 09:31 AM   #8
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by Saturn Night View Post
If you have slipping clutches, the input turbine sensor will set a DTC and the PCM will lockout that gear. The code will scan as "No xx gear/Incorrect ratio".

With OBD-II, it will be P0731-P0734 codes for slipping clutch packs.

No tests, other than pulling the valve body and performing air tests on the clutch packs.

Lockup should occur between 18-25 mph in 2nd gear, and 3rd/4th should also lockup. The TCC only locks in 1st gear when the PCM detects WOT.
The transmission shifts very smoothly. I really can't feel when it upshifts through the gears.

There are no P0731-P0734 codes. Just the feeling that RPM is increasing w/o a corresponding increase in speed as I mash the throttle.

Would a video of the cluster when I mash the throttle help diagnose this issue?
...
1/28/2019 2002 SL2 w 62k miles
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Old 08-12-2019, 09:51 AM   #9
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1998 SC2
Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Not all years of these cars have the automatic programmed the same.
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Old 08-12-2019, 11:14 AM   #10
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

4.063 is what I saw on "sixth sphere", but that is only the ratio at the diff spur gears, not the over-all ratio from engine to axles. Is there some confusion there? And, of course, there is some "ratio" in the converter that is indeterminate until the TC is locked fully.

Use live-data if you want to fuss with this more. Observe engine rpm, TSS, VSS, TCC slip, TCC command, and gear commanded; then do the math to see if the lack of codes is reasonable.

PS: That M/Y Accord had several engine options, all considerably larger and more powerful that the Saturn 1.9L

Last edited by billr; 08-12-2019 at 11:26 AM.
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Old 08-12-2019, 03:23 PM   #11
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by Silverblu02SL2 View Post
The transmission shifts very smoothly. I really can't feel when it upshifts through the gears.

There are no P0731-P0734 codes. Just the feeling that RPM is increasing w/o a corresponding increase in speed as I mash the throttle.

Would a video of the cluster when I mash the throttle help diagnose this issue?
Yes, it could help. A detented(partial throttle) downshift will disengage the lockup TCC, as well.
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Old 08-12-2019, 03:24 PM   #12
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by toggenburg View Post
I don't believe the final torque converter drive lockup ratio is 4.063 as stated.
You can use calculations to find the final drive ratio.

https://spicerparts.com/calculators/...rpm-calculator
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Old 08-12-2019, 03:29 PM   #13
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Before you all run off trying to fix something that does not appear to be broke you better investigate the ignition advance/retard under driving conditions.
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Old 08-12-2019, 09:51 PM   #14
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by Silverblu02SL2 View Post
The transmission shifts very smoothly. I really can't feel when it upshifts through the gears.

There are no P0731-P0734 codes. Just the feeling that RPM is increasing w/o a corresponding increase in speed as I mash the throttle.

Would a video of the cluster when I mash the throttle help diagnose this issue?
You may be 'spoiled' with a manual diesel, accustomed to old school feel using a manual as opposed to the rest of us comfortable with slush boxes. In reality, manuals and autos are bathed in xmission fluid so both are really slush boxes. Automatics use more parts compared to manuals.

Autos greatest characteristic is their ability to shift smoothly otherwise we couldn't talk and text while applying eyeliner and blush while driving. I challenge anyone doing those things while rowing gears.

As you may be aware, the greatest 'slip' occurs within autos using torque converters (two turbines, one connected to the xmission, the other to the engine output shaft) using xmission fluid as the fluid coupling to transfer engine power to the xmission to drive the front wheels. Other slip would be the clutch packs for each gear (also bathed in xmission oil). The last portion of slip would be the pulse width modulated pressure control, torque and shift solenoids. As long as the speedometer needle follows the tach needle, everything's fine. Flooring the pedal to maximize engine power forces the xmission to modulate torque, in this case revving to redline before a shift occurs while the tach needle rises quicker than the speedo. The opposite would be the lowest pedal travel resulting in the slowest acceleration, rev shifting at the lowest rpm. Electronically controlled automatics are overtaking most markets, even the exotics with six figure price tags using paddle shifting derived from F-1 technology.
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Old 08-13-2019, 09:06 AM   #15
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by fdryer View Post
.........................

Autos greatest characteristic is their ability to shift smoothly otherwise we couldn't talk and text while applying eyeliner and blush while driving. I challenge anyone doing those things while rowing gears.

............
How about soda in one hand and hambuger in the other? I don't do that anymore since cops are more on the lookout for distracted driving these days. I do not want to tarnish my perfect driving record.

I drove the Saturn yesterday and I could feel the shifts paying close attention to it. I will make a video when I get a chance.
...
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Old 08-13-2019, 09:40 AM   #16
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

OOPS. My error, final drive IS 4.063 as originally stated.
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Old 08-14-2019, 01:07 AM   #17
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Any detected slip will also have the pcm relearning the shiftpressuresfor the clutch packs. When I did the head modification on my old 96 the first drive had it slamming gears relearning the line pressure. It took around 60 miles of driving until it had all the gears figured out.

If itís actually slipping it will slam shift and lock out the gear it thinks is bad or just slam shift every gear.

Like OldNuc says Active knock retard will kill power if you have excessive carbon buildup or piston slap that mimics knock.
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Old 08-14-2019, 08:40 AM   #18
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Don't forget that the NY gas is real close to water and the power of any older car is way low because of it.

I would be looking real hard at the ignition advance and retard instead of trying to fix a transmission that is not broke.
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Old 08-14-2019, 11:43 AM   #19
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

My perception from how this thread started was that the engine would speed up more than the OP expected for how the vehicle speed was increasing. We need the OP to clarify.

If the engine speed is not increasing "too much", the car just seems to be a dog, then the first step is to take compression. Another trick? Go to a used-car lot and take a similar Saturn for a test ride.
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Old 08-14-2019, 02:13 PM   #20
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Default Re: Any tests to determine if my MP7 transmission is slipping or not ?

Quote:
Originally Posted by Silverblu02SL2 View Post
How about soda in one hand and hambuger in the other? I don't do that anymore since cops are more on the lookout for distracted driving these days. I do not want to tarnish my perfect driving record.

I drove the Saturn yesterday and I could feel the shifts paying close attention to it. I will make a video when I get a chance.
When moving slowly on the Cross Bronx Expy outbound to NJ on days when it's basically a three lane parking lot, I had lunches to pass the time at crawling speed. Breakfasts are full bagels from Dunkin' Donuts. I'll bet many drivers were jealous or talked/texted while crawling along. I doubt cops would stop anyone for eating while 'driving' in these daily crawl fests. I rarely see them anyway. It's not something I advocate but after many drives on the CBE, it's easy to calculate when crawling speed occurs and make the best of it. Mine is having the meal I'm going to have anyway except while moving along slower than any drive thru fast food places.

Since you're now attuned to detecting each gear shift in your slush box, you're probably learning the intricacies of automatics as you correlate rpm to speedometer. If you allow for the described slippage in normal autos, you'll slowly come around to less coordination needed in two pedal vehicles so you can enjoy a Starbucks or 7-11 sandwich while jockeying around NYCs auto cross. For all around city traffic, I believe slush boxes are simply easier to use. Out on open roads away from city traffic, manuals can outshine autos for fuel economy simply because drivers can shift to any gear for lowest rpm then change at any time for another gear.
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