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Allison Transmission Info

Oxyacetylene

Oxyacetylene

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I have edited the original post with updated information. The gear ratios posted previously do not appear correct. I took the serial # off mine and called back to ask again. They quoted me the gear ratios for a 3000 series transmission and said there wasn't much information on the MD3070PT. They could not give me the gear ratio for the 1st gear, which is in the transfer case. Anyway, here are the ratios:

1st - unknown, not listed
2nd - 3.49
3rd - 1.86
4th - 1.41
5th - 1
6th - .75
7th - .65
Reverse: -.509

What fluid is best to run in the transmission? A: Allison/Castrol Transynd. I asked about other fluid choices, and was told that Dex III is a step up from the 15w-40, and the Transynd is the best. They said NOT to use Dex 6 as that will cause the seals to harden.

The technician also talked about how time alone (and not just mileage) will deteriorate the fluid. The transmission has a breather tube, which will let moisture in. This mixes with the fluid and forms an acid. The technician said he hoped they had changed the fluid regularly due to this deterioration.

Here is some info I found online: View attachment MT2923EN.pdf
 
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DSD277

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I'm sorry guys, but the links to current Allison trans is like using a current Ford brochure for specs on a on a 1990's Mustang.... they are not the same!

I've avoided posting on this topic because I've been looking for the docs to support what I remember on the Allison World Class trans, hopefully I can find them later, but until then, this is what I remember.
The MD3070 is the same family as the MD3060's with the addition of the transfer class with another lower gear (hence the trans in all wheel drives are a 7 speed). The top 6 speeds are the same as the MD3060. What I remember on the MD3060 id that 4th gear is 1:1 , 5th .75 OD and 6th .65 OD . The WTEC shows 7 gears (on the 3070), but the "automatic" shifting are 2 to 7 . 1st must be shifted into manually for use, once any other gear is selected, 1st is locked out until manually selected again. It is a off road gear to be selected when needed.

In the 90's, MD3060 were used in in all diesel pusher motorhomes and by all the medium duty truck manufacturers with a HP rating of 230 or higher. When Ford first used them, they were the MD3050, 5 speed with the second overdrive programmed out because the .65 was too much of an OD. The MD series of trans are a LOT heavier than any of their replacements.

I will look to see if I had kept the spec sheet from when I was ordering a medium truck back then...:roll:
.
 
73m819

73m819

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DSD277 said:
For those without the TMs. this is the description for the trans and operation
Click to expand...
By reading this, it looks like these trucks are in all wheel drive 100% of the time, just a different % depending on what mode it is in.
 
DSD277

DSD277

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They are all wheel drive, As also implied in my first post. The module that adds the axle front drive (transfer case), also has the 7th speed ( granny 1st).
And just to say it: there is no hi /lo transfer case, just the additional low gear

During my "resurrection" of the FDT, I read a lot on the FMTVs that was wrong or assumptions because of what people thought or read elsewhere on them.
When working on them, do not use any preconceptions because of some other military truck you have/had.
 
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THE MACHINIST

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So if 230hp is not enough power to use the .65 OD in a motor home it probably won't be enough in a loaded m1079 if the final drive gears were changed from 3.9 to 3.55 or 3.07.

If that is the case Has anyone turned the mechanical injection pump up to see how much it helps with a gear swap.

Thanks

jamie
 
DSD277

DSD277

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THE MACHINIST said:
So if 230hp is not enough power to use the .65 OD in a motor home it probably won't be enough in a loaded m1079 if the final drive gears were changed from 3.9 to 3.55 or 3.07.

If that is the case Has anyone turned the mechanical injection pump up to see how much it helps with a gear swap.

Thanks

jamie
Click to expand...
Read my post. FORD used the 3050 (5 spd)when the MDs first became available to Ford medium duty trucks (mid 1994)., motorhomes (w/ 230hp or more) used the 3060 (6 spd). (FYI) MHs with 190 HP diesel used the Allison 540 series trans (lacked lock up), so you'd lose 3 to 4 mph from geared speed.

If you re-ratio the rear end too high, the trans may not shift into top gear, especially pulling a grade or with a load, being useable for down hill without a load against it... simply a waste of a trans and gears. So it comes down to if you live and drive mostly flatlands, the highest rear end ratio could be fine, but if you live and drive in mountains, the stock ratio may be your best overall choice.
 
Oxyacetylene

Oxyacetylene

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DSD277 said:
I'm sorry guys, but the links to current Allison trans is like using a current Ford brochure for specs on a on a 1990's Mustang.... they are not the same!

I've avoided posting on this topic because I've been looking for the docs to support what I remember on the Allison World Class trans, hopefully I can find them later, but until then, this is what I remember.
The MD3070 is the same family as the MD3060's with the addition of the transfer class with another lower gear (hence the trans in all wheel drives are a 7 speed). The top 6 speeds are the same as the MD3060. What I remember on the MD3060 id that 4th gear is 1:1 , 5th .75 OD and 6th .65 OD . The WTEC shows 7 gears (on the 3070), but the "automatic" shifting are 2 to 7 . 1st must be shifted into manually for use, once any other gear is selected, 1st is locked out until manually selected again. It is a off road gear to be selected when needed.

In the 90's, MD3060 were used in in all diesel pusher motorhomes and by all the medium duty truck manufacturers with a HP rating of 230 or higher. When Ford first used them, they were the MD3050, 5 speed with the second overdrive programmed out because the .65 was too much of an OD. The MD series of trans are a LOT heavier than any of their replacements.

I will look to see if I had kept the spec sheet from when I was ordering a medium truck back then...:roll:
.
Click to expand...
The gear ratios you quoted make sense. I just tried out a gearing calculator online and plugged in values. If I use the adjusted tire size measurement to account for squat of the tire, then the .65 ratio seems pretty close for the RPM's I was seeing at 50MPH. I was able to get the serial # off mine, so I can call them to confirm and then update the original post. Thanks!
 
Oxyacetylene

Oxyacetylene

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OK I called back and gave them the serial #. They quoted me the ratios that DSD277 posted above. They gave me the specs for a 3000 series transmission, and said there wasn't much information on the MD3070PT.
1st - unknown, not listed
2nd - 3.49
3rd - 1.86
4th - 1.41
5th - 1
6th - .75
7th - .65
Reverse: -.509

From a "seat of the pants" perspective it does seem that going from 2nd to 3rd gear is when the truck really takes off. This would correlate with the bigger change in ratio from 2nd to 3rd gear vs the other gears.
 
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R

royalflush55

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Oxyacetylene said:
OK I called back and gave them the serial #. They quoted me the ratios that DSD277 posted above. They gave me the specs for a 3000 series transmission, and said there wasn't much information on the MD3070PT.
1st - unknown, not listed
2nd - 3.49
3rd - 1.86
4th - 1.41
5th - 1
6th - .75
7th - .65
Reverse: -.509

From a "seat of the pants" perspective it does seem that going from 2nd to 3rd gear is when the truck really takes off. This would correlate with the bigger change in ratio from 2nd to 3rd gear vs the other gears.
Click to expand...
I am not familiar with these S&S vehicles, but is reverse .509 or 5.09 ratio?
 
Awesomeness

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Hawssie said:
I know this is an old thread but as I was interested in 3070 transmissions I came across it. I may have found the ratios as well:http://www.allisontransmission.com/...sheets/int3700_sa5343(201306)blk.pdf?sfvrsn=2
Does anyone know of a source for wiring harness and transmission computer for one of these?
Click to expand...
Did anyone ever confirm if the true gear ratios are those listed in the first post, or in this Allison brochure which states:

First 6.93 : 1
Second 4.18 : 1
Third 2.24 : 1
Fourth 1.69 : 1
Fifth 1.20 : 1
Sixth 0.90 : 1
Seventh 0.78 : 1
Reverse -5.00 : 1
 
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R

Ronmar

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Awesomeness said:
Did anyone ever confirm if the true gear ratios are those listed in the first post?
Click to expand...
Yes they are, and they aren’t:) Those six ratios listed are the core ratios out of the 3000 series transmission which the 3070 uses for 2nd thru 7th gear. The transfer case applies an additional 1.2:1 ratio in fixed gearing. When you multiply those ratios by 1.2 you get the final driveshaft output ratios you listed. That is why 5th is a 1.2:1 ratio as the core transmission is a straight thru 1:1 ratio in that gear. These are also the same ratios listed for the 3700 AWD/4WD transmission.

GR RATIO CLUTCH
1st 6.93:1 C3-C6
2nd 4.18:1 C1-C5
3rd 2.24:1 C1-C4 + LU
4th 1.69:1 C1-C3 + LU
5th 1.20:1 C1-C2 + LU
6th 0.90:1 C2-C3 + LU
7th 0.78:1 C2-C4 + LU
R -5.00:1 C3-C5

We get our low first gear from the C6 clutch located in the transfer case, but it does its magic inside the core transmission.

The output of the transmission comes from the P3 planetary gear carrier. The splined output shaft on the P3 carrier plugs into and drives the top gear in the transfer case via an adapter. That P3 carrier spline, the adapter and the transfer case primary drive gear are hollow. Thru them runs the transmission main shaft which has the P2 and P3 sun gears on it. That mainshaft runs from C1 at the front in the rotating clutchpack thru all the planetaries and the transfer case to reach the C6 clutchpack. The combination of stopping the mainshaft with C6 and applying drive from the rotating clutchpack via C3 gives you that very low 1st gear ratio.

Since the math tells me the 3060 ratios for 1st-6th multiplied by the 1.2:1 transfer case equal the 2-7 ratios for the 3700 transmission, I am assuming the planetaries use the same ratio gearsets. That being the case, the 6.93:1 first gear ratio must be the same between the 3070 and 3700...
 
Last edited:
Awesomeness

Awesomeness

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Ronmar said:
Yes they are, and they aren’t:) Those six ratios listed are the core ratios out of the 3000 series transmission which the 3070 uses for 2nd thru 7th gear. The transfer case applies an additional 1.2:1 ratio in fixed gearing. When you multiply those ratios by 1.2 you get the final driveshaft output ratios you listed. That is why 5th is a 1.2:1 ratio as the core transmission is a straight thru 1:1 ratio in that gear. These are also the same ratios listed for the 3700 AWD/4WD transmission.

GR RATIO CLUTCH
1st 6.93:1 C3-C6
2nd 4.18:1 C1-C5
3rd 2.24:1 C1-C4 + LU
4th 1.69:1 C1-C3 + LU
5th 1.20:1 C1-C2 + LU
6th 0.90:1 C2-C3 + LU
7th 0.78:1 C2-C4 + LU
R -5.00:1 C3-C5

We get our low first gear from the C6 clutch located in the transfer case, but it does its magic inside the core transmission.

The output of the transmission comes from the P3 planetary gear carrier. The splined output shaft on the P3 carrier plugs into and drives the top gear in the transfer case via an adapter. That P3 carrier spline, the adapter and the transfer case primary drive gear are hollow. Thru them runs the transmission main shaft which has the P2 and P3 sun gears on it. That mainshaft runs from C1 at the front in the rotating clutchpack thru all the planetaries and the transfer case to reach the C6 clutchpack. The combination of stopping the mainshaft with C6 and applying drive from the rotating clutchpack via C3 gives you that very low 1st gear ratio.

Since the math tells me the 3060 ratios for 1st-6th multiplied by the 1.2:1 transfer case equal the 2-7 ratios for the 3700 transmission, I am assuming the planetaries use the same ratio gearsets. That being the case, the 6.93:1 first gear ratio must be the same between the 3070 and 3700...
Click to expand...
Ok, lots of good info there. To make sure I'm understanding, I think you are saying that all the ratios listed in the first post of this thread are the mechanical ratios in the 3000 series transmission itself. Our 3070 includes the transfer case, which adds a 1.2:1 ratio to everything (except the first gear), giving the ratios listed in the Allison brochure above (which I posted above too). But those ultimate numbers from the brochure (which I posted too) are correct for the transmission+transfer case as a unit? Is that correct?
 
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