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Gear ratio dilemma

2000StreetRod

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Greenville, SC
Year, Model & Trim Level
00 Sport FI, 03 Ltd V8
I have a 2000 Explorer Sport with SOHC and 5 speed automatic transmission. When I purchased the vehicle in May 2009 it came with the original Owner's Guide that specifies that the 5 speed transmission is the 5R55E. The trailer towing table in the guide lists 3 possible rear axle ratios: 3.27, 3.55 and 3.73:1. The Certification Label on the driver door lists "D" under TR which decodes to 5R55E for year 2000 and "46" under AXLE which decodes to 3.73:1 open differential. The published gear ratios for the 5R55E are: 1st, 2.47; 2nd, 1.86 (2.47*.75); 3rd, 1.47; 4th, 1.00; and 5th, 0.75. I have not found any documented variations of the 5R55E with different gear ratios. The torque converter can add additional variable gear multiplication or lock at 1:1.

In the fall of 2009 my Sport was performance tested on a Dynojet dynomometer in 2nd and 4th gears. The Dynojet only utilized the vehicle ignition spark to determine engine speed and independently determined vehicle speed. The dyno test results verified the 3.73:1 rear axle ratio but not the 2nd gear ratio of 1.86:1. The dyno derived 2nd gear ratio appears to be about 1.54:1 which means 1st gear is about 2.05:1 (1.54/0.75).

Recently I purchased an X3 Power Flash with custom tune and have accomplished several data logging exercises for the tune development. The PCM receives vehicle speed data from the rear axle mounted vehicle speed sensor that is independent of transmission gearing. The data logs substantiate nonstandard gear ratios for 1st (2.05:1), 2nd (1.54:1) and 3rd (1.22:1) gears. It is my understanding that the torque converter does not have any overdrive capability.

I requested that my custom tune WOT upshift points be based on the standard published gear ratios to maximize acceleration. If I have nonstandard gearing then I may need to change my upshift points.

Has anyone heard of a close ratio 5R55E possibly exported to other countries? I believe that the vehicle original owner was military and may have purchased my Sport outside the U.S. Can anyone think of another explanation for the apparent nonstandard gearing?
 



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Just a bump for the gurus... I couldn't even find the specific stock gear ratios for the trans in the service manual... No idea where to go from there, but I know someone here will have some clues...
 






You said that the dyno accurately reflected the 3.73 rear end ratio, but that the calculations were off a bit (really, a very small amount) for the 2nd gear trans ratio.

There is a reason why dyno runs generally aren't done in 2nd gear. It will distort torque/hp numbers, as you already know. However, the reason this occurs is because you are getting torque multiplication from the gear reduction in the tranny, as opposed to running 4th gear (1:1). This additional torque is more likely to result in a slight (perhaps unnoticed) amount of tire/wheel slip on the dyno rollers. Therefor resulting in a slower roller speed for a given engine rpm, and it would take longer to accelerate the rollers. This would look like a numerically lower gear ratio (taller), which produce less acceleration, in exchange for higher top speed.
Unless the tune was written to do so, I don't think that the torque convertor locks in a 2nd gear accleration run, whereas, in 4th I think (not sure) that it would. If this is the case, that 2nd gear run now has additional "slippage" and a further extended time to accelerate the drum, again appearing as a "taller" gear.

The final possability regards the dyno itself. If the dyno "calculates" gear ratio from 1 or more other "calculations", instead of direct data, then you could also have errors due to tolerance stacking.

Of course, I could also be completely wrong about everything I just said, but it seems to make sense to me.:D Just my $.02
 






Gear ratios for the various 5R55x Ford transmissions...

I can't say that I have ever heard of a close ratio 5R55E tranny... Now the 5R55s and 5R55W have different ratios as does the 5R55N...

The list below are what I found as the ratios for the various trannies...

5R55E

Gear Ratios:
2.47:1 1st gear
1.86:1 2nd gear
1.47:1 3rd gear
1.00:1 4th gear
.75:1 5th gear
2.10:1 reverse

5R55N

Gear Ratios:
3.25:1 1st gear
2.44:1 2nd gear
1.55:1 3rd gear
1.00:1 4th gear
.75:1 5th gear
3.07:1 reverse

5R55S

Gear Ratios:
3.22:1 1st gear
2.29:1 2nd gear
1.55:1 3rd gear
1.00:1 4th gear
.71:1 5th gear
3.07:1 reverse

5R55W

Gear Ratios:
3.22:1 1st gear
2.41:1 2nd gear
1.55:1 3rd gear
1.00:1 4th gear
.75:1 5th gear
3.07:1 reverse


The 5R55E was used in the 1997 MY in various cars and trucks. The 5R55N is primarily used in the 1999 Lincoln and Jaguar products where the 5R55S and the 5R55W are used in trucks and some cars starting in 2002...
 






Dyno errors

You said that the dyno accurately reflected the 3.73 rear end ratio, but that the calculations were off a bit (really, a very small amount) for the 2nd gear trans ratio.

There is a reason why dyno runs generally aren't done in 2nd gear. It will distort torque/hp numbers, as you already know. However, the reason this occurs is because you are getting torque multiplication from the gear reduction in the tranny, as opposed to running 4th gear (1:1). This additional torque is more likely to result in a slight (perhaps unnoticed) amount of tire/wheel slip on the dyno rollers. Therefore resulting in a slower roller speed for a given engine rpm, and it would take longer to accelerate the rollers. This would look like a numerically lower gear ratio (taller), which produce less acceleration, in exchange for higher top speed.

Thanks for your ideas! The difference between the published 2nd gear (1.86) and my measured/computed 2nd gear (1.50) is 18 mph at 6000 rpm. I agree that the max power is going to be different for 2nd vs 4th because the dyno only measures ft-lbs/sec and then divides the number by 550 to determine horsepower. The dyno roller speed is totally independent of the vehicle axle and transmission gearing and the tire diameter. The dyno determines vehicle speed by using the circumference of the drum times the rotation speed of the drum. The dyno records the engine rpm from the ignition and the drum rotation rate to determine vehicle speed vs engine speed.

If my wheels were breaking loose from the drum then the drum would spin slower per engine rpm and the gearing would appear to be more engine speed per vehicle speed instead of less.

Unless the tune was written to do so, I don't think that the torque convertor locks in a 2nd gear accleration run, whereas, in 4th I think (not sure) that it would. If this is the case, that 2nd gear run now has additional "slippage" and a further extended time to accelerate the drum, again appearing as a "taller" gear.

In the process of developing my custom tune I have performed stop to high engine speed 2nd gear runs on the highway and recorded data with my X3. When plotting the datalog I can see the rpms drop between 2000 and 3000 rpm while vehicle speed is rapidly increasing. This is when the torque converter is reducing its multiplying to attain 1:1 gear reduction although technically it may not be locking. The equivalent 2nd gear ratio I compute for these tests agrees with the dyno tests.

The final possability regards the dyno itself. If the dyno "calculates" gear ratio from 1 or more other "calculations", instead of direct data, then you could also have errors due to tolerance stacking.

Of course, I could also be completely wrong about everything I just said, but it seems to make sense to me.:D Just my $.02

The dyno does not compute the gear ratio. It only provides plots of engine speed vs vehicle speed. From that I am able to compute the equivalent gear ratios.

overall ratio = (engine rpm)*[tire diam(inches)]/mph*336

transmission gear ratio = overall/3.73(rear axle)

If anyone has their 5R55E torn apart, I'd sure like to know how many teeth are on the gears and their mates.
 






trans table

Thanks for posting the transmission table ranger7ltr. I'm surprised that the 5R55E used in the greater weight Explorer has a higher speed 1st gear than the 5R55S used in the 2005+ lighter weight Mustangs. I guess that Ford decided to change the rear axle ratio instead.

Is there usually an identification tag attached to the transmission or an identification plate mounted on it? Even with the cold weather we're having in the South now I'm about ready to climb under the vehicle to see if I can find something to confirm the transmission type. Or maybe I'll find a long uphill grade and slowly accelerate thru all the gears while data logging.
 






gear ratio datalog

This morning I logged data for numerous upshifts at various throttle settings and going uphill. I analyzed the data and computed gear ratios for instances where the throttle was steady and the engine speed and vehicle speeds were increasing. I then factored in a VSS correction factor for the difference in my tire size and that assumed by the VSS/PCM. The correction factor (1.04) resulted in a 4th gear ratio of 1:1 and an overdrive ratio of 0.75:1. The derived mechanical gear ratios are as follows:

1st 1.97:1
2nd 1.45:1 (agrees with 1.97*.75=1.48)
3rd 1.22:1
4th 1.00:1
5th 0.75:1

Next I plan to slide under my Sport and visually inspect the transmission for any identification markings, plate or tag. I'm still searching for an explanation for the nonstandard gearing.
 






What is the Maximum RPM for each gear? Say for 2003 Explorer V6 engine and 5R55W transmission what is the max RPM in each gear beyond which the engine noise level is too high.
like this:
Gear rpm mph
----- ----- ------
1
2
3
4
5
 






rev limit

I believe the stock rev limit for my 2000 SOHV is 6250 rpm. It's the same for all gears. One thing I don't like about the 5R55E is there is no way to control 3rd gear. Ford should have added another shift select position when going from 4 gears to 5 gears.
 






"2" gear selection puzzle explained

On another thread PopRichie77 has explained why my rpm vs vehicle speed was significantly in error when "2" was selected on the shift column selector. The reason is that selecting "2" is actually selecting the 3rd gear ratio of 1.47:1 instead of the 2nd gear ratio of 1.86:1. All of my custom tune WOT testing was done from a standing start with "2" selected so the transmission would never shift. Until now I erroneously assumed that "2" meant 2nd gear. I always thought that it was poor that Ford provided no way to manually downshift to 3rd gear when the engine was loaded down in 4th gear. Now I know they did provide the capability, they just forgot to document how to utilize it. Thanks again PopRichie77!
 






Chart

08-24-2010 12;03;22AM.jpg
 






Informative chart

Thanks for posting the very informative 5R55E chart! It clearly shows that "Manual 2" is 3rd speed. It would have saved me a lot of time when I was connecting my remote oil filter since it identifies the upper port as the cooler return line. The quick way to distinguish the 5 speed from the 4 speed by the output speed sensor location is also helpful. I'm sure the Clutch/Band/Solenoid Application Chart is essential for troubleshooting problems.
 






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