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Discussion Starter #1
This Promaster transmission has no reserve power in 6th gear at highway speed. Even after 22500 miles, with or without a load, it drops to 5th on inclines. It climbs in 5th just fine, but at over 3000 rpms, and less than 10 mpg. This performance is dramatically worse than my 2013 Toyota Sienna v6 and my previous 2012 Toyota Sienna minivan with a 185hp 2.7 liter 4 cylinder engine. While the Promaster is higher profile and about 700 lbs heavier, 3000 rpms in 5th gear just doesn't make sense, and is causing excessive wear on the drivetrain. The Chrysler engineering team should reprogram the transmission for 4th, 5th, 6th gears and the torque converter clutch.
 

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Going uphill requires a lot more power which accounts for the 10 MPG while climbing. Even if transmission stayed in 6th (and I doubt engine could pull it), fuel economy would still drop drastically while going uphill. That's normal and should be expected.

I had a car that would do around 22 MPG while cruising, and could easily drop to around 10 MPG going uphill. On the downhill side it would sometimes peg computer at 99 MPG. And my car stayed in high gear because it didn't need to downshift.

We shouldn't confuse required added power with engine speed as the only cause of added fuel burn rate. They are related but not equals.
 

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Are you using tow/haul mode? If not you should be. Engine speed with a smaller throttle opening doesn't mean more fuel used. In these modern computer controlled, fuel injected engines, it means less, unlike the old carbureted engines.
What drivetrain wear?
 

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Are you using tow/haul mode? If not you should be. Engine speed with a smaller throttle opening doesn't mean more fuel used. In these modern computer controlled, fuel injected engines, it means less, unlike the old carbureted engines.
What drivetrain wear?
As long as you're not lugging the engine & you don't run out of power & you're not at WOT (which is usually set up to be richer) lower revs is almost always better fuel economy than higher revs. Look at any typical brake specific fuel consumption chart. Wish we had one for this engine.
I think it shifts down sooner than it should but there is no way to prove that since you can't stop the downshift. Also the PM has too large of a gap between 5 & 6.
 

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As long as you're not lugging the engine & you don't run out of power & you're not at WOT (which is usually set up to be richer) lower revs is almost always better fuel economy than higher revs. Look at any typical brake specific fuel consumption chart. Wish we had one for this engine.
I think it shifts down sooner than it should but there is no way to prove that since you can't stop the downshift. Also the PM has too large of a gap between 5 & 6.
It's hard to know exactly when PMs are downshifting on up hills according to various reports, but simple math confirms that there is no way whatsoever that an 8,000 pound van can hold 70 MPH on a long and steady 5 percent grade without dropping out of 6th gear. Power requirement nearly triples, and the engine would have to produce in excess of 300 lb-ft of torque at about 2000 RPM if it were to stay in 6th with a locked torque converter. An obviously the engine can't produce over 300 lb-ft of torque at any RPM.

Even when the transmission shifts to 5th gear and engine RPM goes up to around 3000 at 70 MPH, the engine still has to produce over 200 lb-ft of torque to hold speed on 5 percent grade. And any torque above 200 lb-ft makes the engine efficient enough that there would be no need to try holding a wide open throttle just to keep revs lower in 6th gear. Engineering wise it would be counterproductive.

A lot of the assumptions being made are inherently flawed because they are often asking for the impossible. In my opinion we should trust that RAM power train engineers know what they are doing for the most part.
 

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From my math, 60 mph / 100 km/h is about 1400 rpm in 6th with torque converter locked using the final drive that the 1500 models use. Full torque at that speed (if the controls allowed it, which they probably don't) would be somewhere around 65 horsepower.

Aero drag should use around 30 horsepower, tires etc will probably use up another 5 or 10, and one can see that it is going to be using a good chunk of what power is available at such low revs just pushing itself through the air. Stiff headwind, slight uphill, etc and it's going to need a downshift.

Engines have the highest efficiency when they are using most of their available torque (at the slowest possible revs that will deliver the required power), so from the engineering point of view, they are not wrong to gear it this tall. It will get the best mileage that can be expected. It's going to need downshifts on hills.

Don't have my van yet so I'm only going by my short test drive, and the transmission seemed unobtrusive. I am going to operate on the assumption that Chrysler engineers knew it would need lots of gear changes when the vehicle was designed, and the transmission is designed to handle it, and just let it do what it wants.
 

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Discussion Starter #8
This tranny has been downshifting to 5th since day one, and it has actually gotten better. When I say "inclines" I mean anything slightly steeper than a freeway overpass, which is not even a 3% grade. By comparison, my 2013 Toyota Sienna v6 does not downshift in the same situation. On a trip from Jacksonville Florida to Indianapolis, the truck was downshifting every few minutes, even in Tow Haul Mode, with less than 1000 lb load. I found a video online of a Chrysler Town and Country minivan performing the same way at 73 mph. This van performs this way at any speed above 60 mph. Headwinds are worse, and I have to drive behind an 18 wheeler if I want the van to get into 6th and get more than 14 mpg highway. In my interstate delivery business, I'm looking at an additional $3,000 - $5,000 per year in fuel costs. If 5th gear were set at 2300-2500 rpms, the downshifting and fuel economy would be okay.
 

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This tranny has been downshifting to 5th since day one, and it has actually gotten better. When I say "inclines" I mean anything slightly steeper than a freeway overpass, which is not even a 3% grade. By comparison, my 2013 Toyota Sienna v6 does not downshift in the same situation. On a trip from Jacksonville Florida to Indianapolis, the truck was downshifting every few minutes, even in Tow Haul Mode, with less than 1000 lb load. I found a video online of a Chrysler Town and Country minivan performing the same way at 73 mph. This van performs this way at any speed above 60 mph. Headwinds are worse, and I have to drive behind an 18 wheeler if I want the van to get into 6th and get more than 14 mpg highway. In my interstate delivery business, I'm looking at an additional $3,000 - $5,000 per year in fuel costs. If 5th gear were set at 2300-2500 rpms, the downshifting and fuel economy would be okay.
Can I ask why you went with the gas engine? Because of the delay?
My opinion is the diesel would of solved all the problems you are saying.

Which van do you have 2500 or 3500. The reason I ask is because I read
that the 3500 has lower 5th and 6th gear.

I ordered the gas as well because of the emission/delay and cold cold
winters here (Canada).

I have also a ram 1500 4x4 pick up and I drive with the tow mode on except the flat highways because it cant make up its mind on what gear to stay in.
 

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This tranny has been downshifting to 5th since day one, and it has actually gotten better. When I say "inclines" I mean anything slightly steeper than a freeway overpass, which is not even a 3% grade. By comparison, my 2013 Toyota Sienna v6 does not downshift in the same situation. On a trip from Jacksonville Florida to Indianapolis, the truck was downshifting every few minutes, even in Tow Haul Mode, with less than 1000 lb load. I found a video online of a Chrysler Town and Country minivan performing the same way at 73 mph. This van performs this way at any speed above 60 mph. Headwinds are worse, and I have to drive behind an 18 wheeler if I want the van to get into 6th and get more than 14 mpg highway. In my interstate delivery business, I'm looking at an additional $3,000 - $5,000 per year in fuel costs. If 5th gear were set at 2300-2500 rpms, the downshifting and fuel economy would be okay.
If 5th gear was set for 2300-2500 RPMs at 70 to 73 MPH, then 6th would be so tall a gear that it would be useless other than for going downhill.

The only way to get what you are asking is to either have a larger engine that would not need to downshift, or a transmission with closer gear steps. If so, to provide the necessary gear range would require more gears. If RAM installed a heavy duty version of the 9-speed automatic in the PM, then shifts from 9th to 8th on hills would limit engine speed well below 3000 RPMs.

Of course, if gear ratios are too close, there is the chance the transmission would have to make multiple shifts. Like going from 9th to 8th and then to 7th in order for the engine to handle the high horsepower load.
 

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If 6th gives 1400 rpm at 60 mph (1500 model) then 5th should be around 2100 rpm. The 2500 models are about 10% higher revs in both cases based on the final drive.

As for the closer gear steps ... Yes, that would be nice, particularly in the higher gears. The issue here is that the Chrysler 6-speed front-drive automatic is really a 4-speed automatic with an additional "range box". Theoretically that gives 8 possibilities, but some of the combinations are not used, and some of the steps between ratios are odd. 2nd and 3rd are closer together, percentage-wise, than 5th and 6th.

The 9-speed auto would be interesting in this vehicle ... but if anything, it would shift more than the 6-speed does. I suspect that Chrysler is saving that transmission for the vehicles that need the corporate-average-fuel-economy bump; 3/4 ton and bigger trucks don't figure into that.
 

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From my math, 60 mph / 100 km/h is about 1400 rpm in 6th with torque converter locked using the final drive that the 1500 models use. ,,,,,,,,,cut.............
I've seen data indicating that 1500 models have a final ratio of 3.15 (going from memory), but it's hard to understand why anyone would gear a van to run over 40 MPH per 1000 RPM. Even my Honda minivan with similar size engine is limited to 36 MPH per 1000 RPM. And a minivan is much smaller to the wind and has a much lower GCWR.

Other data suggesting all PM vans have same final drive ratio makes more sense to me, particularly if they will have the same 11500 pound GCWR.
 

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I saw a spec sheet which showed 3.16, 3.43, and 3.86 diff ratios for the 1500, 2500, and 3500 respectively, but the one I found here
http://chryslermedia.iconicweb.com/m...oMaster_SP.pdf
shows 3.86 for all. That is still a pretty tall gear with the 0.65 6th gear. If that spec sheet is correct and my math is correct that results in 34.7 mph/1000rpm for 6th and 23.76 for 5th. If that is correct then at 65 mph it would be 1873 rpm in 6th and 2743 in 5th. My recollection from my test drive does not agree with this, I thought is was reving higher. If those numbers are correct then I could see that it would have to downshift for almost any grade, its off the bottom of the torque curve.

My memory could be wrong, or this spec sheet is outdated. Perhaps someone who has one could take note of the rpm/speed in 5th and 6th. I'm curious now.
 

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For a modern 6-speed transmission, the 62TE that comes with the V6 does have very wide gear spacing at the top end. 6th to 5th is 1.46, and 5th to 4th is 1.44. A downshift in this range causes engine speed to jump from 2000 to 3000 RPM or more when torque converter slip is factored in.

By comparison the Fiat automated manual has a step of 1.27 between 6th and 5th and a step of 1.37 between 5th and 4th.

The ZF 9 speed has steps of only 1.21 between 9th and 8th and also between 8th and 7th. If it double shifted down from 9th to 7th the combined gear step would be 1.46, the same as the 62TE going from 6th to 5th. Basically the 9speed adds an extra gear in the middle of the step.

If we look at gear ratios for Ford rear-wheel-drive 6-speed transmissions like the one to be used on new Transit, we'd find steps between the higher gears are much closer than on PM's 6-speed auto. Chrysler could do better with transmission ratios to prevent some of these reported issues.
 

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^ It's like that because Chrysler took the old 4-speed automatic gearset and added another "range box" behind it ...

Theoretically there are 8 possible combinations but not all of them are used. This transmission actually has two different possible ratios for 4th gear (so it is a "7 speed"). They are too close together to bother shifting through them. It just picks one or the other depending on circumstances.
 

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I did some poking around and as brian and chance said it's basically the 4 spd tranny with another set of gears. IMO they really screwed it up. It's essentially the 2,3,4 ratios from the 4spd with the extra gears being lower than 1 and between 1 & 2. This might be good for a heavy load in the city, but for hilly highway driving its a deal killer for me. It's too bad because I'd probably buy the gas PM if it weren't for this.

http://www.allpar.com/mopar/transmissions/41TE.html
http://www.allpar.com/mopar/transmissions/62TE.html
I found a spec sheet on PM somewhere (don't have the link) which had slightly different ratios than the allpar info, but it's similar, just slightly higher gearing, same spacing between gears & they don't list the 4-prime that allpar shows.
 

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i dont know gear ratios that well but is the solution to have a final gear that is higher so RPMs are lower on the highway?
 

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i dont know gear ratios that well but is the solution to have a final gear that is higher so RPMs are lower on the highway?
I don't think it's that simple. The RPM at highway speed can be controlled by changing the final ratio, much like changing the rear axle ratio on a rear-wheel-drive vehicle. The underlying problem with the PM's transmission that seems to be causing some of the issues is that Chrysler took a 4-speed auto and then added a "underdrive" unit so they could use it on heavier vehicles, or else to use taller gearing and still have the ability for the vehicle to get moving off the line. It's a bad compromise and not at all what would happen if they started with a clean sheet of paper and designed a proper 6-speed automatic.

I found a transmission web site that list the gear ratios for the PM's 62TE transmission. And they are identical to what they also list for the 4-speed F4AC1, which appears to be in the 41TE family. From what I can tell, Chrysler added a 1.452:1 underdrive to the 4-speed transmission to make the 6-speed. As Brian mentioned in a previous post, it would make an "8" speed in theory, but some of the ratios would repeat. As it stands it's actually a "7" speed because it appears to use a different "4th" gear on the way up versus when downshifting. There is only a slight difference between these two "4th" gears. I expect they do it in part to get more even wear of the transmission, although they claim it also leads to smoother shifting.

Anyway, here are the listed gear ratios from this site which work out exactly if the combined gearing is multiplied out:

1 - 2.842
2 - 1.573
3 - 1.000
4 - 0.689

By adding what I think is the 1.452 underdrive unit in series they get:

1 - 4.127
2 - 2.842
3 - 2.284
4 - 1.573
4 - 1.452 (they call this ratio 4th prime)
5 - 1.000
6 - 0.689


From this we can see that the point papab made is correct. It appears that the top three gear steps are essentially the same. So once on the road at highway speed any necessary downshfts are no better than if the transmission had been a 4-spped.

In a way it makes it worse, because if it had been a 4-speed they would have had to use lower final ratio (in order to get vehicle moving off the line) which would have avoided some of the "overdrive to direct" downshifting that many on this forum have noted.

A properly-designed 6-speed transmission would have wider ratios in the lower gears and closer steps as it shifted towards the top gears. That's what we typically see with 6-speed Ford or 8-speed RAM autos designed by ZF. The 9-speed FWD ZF used by Chrysler also follows this logic.
 

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P.S. -- The one ratio that is a complete duplicate would be the underdrive of the overdrive. That is, 1.452 X .689 is no different than using the "direct" 1:1 ratio.
 
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