Five Speed Automatic Envy?

[Boldt's Wagon]

Have you been thinking you would like to have the Allison or new Ford 5 speed automatic transmissions?



I looked up the gear ratios for the big 3 diesel automatics:



Allison 1000

Granny Low = 3. 1

1st = 1. 81

2nd = 1. 41

3rd = 1. 00

OD = 0. 71

Reverse = -4. 49



Ford 5R110W

Granny Low = 3. 09

1st = 2. 2

2nd = 1. 54

3rd = 1. 00

OD = 0. 71

Reverse = -2. 88



Dodge 47/48RE

1st = 2. 45

2nd = 1. 45

3rd = 1. 00

OD = 0. 69

Reverse = -2. 21



Notice that the 5 speeds give you 2 low gears and do not significantly change the top 3 gears (called OD, 3rd, and 2nd in this posting) from the values for the 47/48RE transmission. The Ford 5R110W top three gear ratios are identical to the 4R100 transmission. Ford changed 1st gear from 2. 71 to 2. 20 and added another 3. 09 lower gear. I have not noticed any problem with the 1st gear 2. 45 ratio in the 47RE and probably would not need another lower gear. People with 4 wheel drive have access to low range if they need another lower ratio.



It appears that the hyped 5 speeds give you:

1) arguably higher torque ratings (also available with the 48RE);

2) lockup in 1st, 2nd, 3rd, and OD;

3) higher shift points in tow/haul mode; and

3) automated downshifting when braking in tow/haul mode.



I see no compelling advantage for the 5 speed autos offered by GM and Ford. The 2nd, 3rd, and OD gear ratios of most interest for towing are effectively the same as the 47/48RE transmissions.



The 47RE transmission rebuilders and the new 48RE can give the Dodge higher torque ratings.

Lockup in 1st, 2nd, 3rd, and OD is available for the 47RE with valve body modifications and electronic boxes.

Higher lockup speeds and higher OD shift speed are available for the 47RE with electronic boxes.

Downshifting when braking has to be provided by the bionic computer behind the steering wheel.

 

[JoeyD]

How can you say you see no advantage? What about a wrecker company that spends it's time in town and never gets to cruise in high gear? Even the weekend hauler will enjoy a better launch with either of the 5spd autos. You can't drive on the highway all the time.

 

[Boldt's Wagon]

My DTT torque converter launches by taking my foot off the brake. An idle will get up to 10 mph and shift into second.

 

[WyoJim]

Boldt's Wagon... . An informative post. Thanks for pointing it out.

 

[Midnite]

Given such a low 1st gear, I would think anyone who has to manuver a heavy load around would like it. Less reliance on fluid coupling--sort of like not having to slip the clutch so much.



Can you get the Allison 1000 with a retarder?



Mike

 

[Boldt's Wagon]

With 2 low or 4 low the transfer case 2. 72 reduction gives a total reductiion of 6. 66 in low gear-low range.

 

[JoeyD]

If 6. 6 is good, then 8. 432 must be better.

 

[LSMITH]

I envy the 5 speed allison because it works like an auto should!!! AND it does it right out of the box!!! It shifts up and down to keep the DMax right where it needs to be, and is not in the wrong gear EVER. When was the last time your super dee duper aftermarket whiz bang 47RE (of any aftermarket brand BTW) downshifted right down to 1st as you were coming to a stop using the compression to help stop you all by itself? When was the last time you rounded a corner at 15 miles per hour and it dropped to second all by itself so you could come out of the corner in the right gear without kicking it down? When was the last time you nailed it only to have it downshift for that all important last 75 RPM of the next gear down?



Gear ratios? I could care less about the 1st vs 1st. I want one to work right.



The 47RE SUCKS compared to a fully electronic transmission in useability. There are a few tricks the builders can do and make them quite nice, but they have only a small portion of the leeway a fully electronic transmission does. The electronic trannies can be made to do whatever you want, with ours it is give and take. Change this and that changes, get that right and now this is not quite what you want. Such is the nature of hydraulics circuits with no overrides. A manual valvebody is as close as we will get to the allison with the 47RE, then YOU can decide what happens when instead of a lame "tuned for one situation and hope it works OK for the rest" setup.