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Is there any automatic transmission for a 3/4 ton truck sturdier than Chevy's Allison?

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Originally posted by: Electric Amish
I don't know why someone would buy a truck and then put an automatic in it....


amish
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Because they have higher tow ratings due to their superior stregnth. also with their current gearing you have great low end and you lose no momentem when towing or boost if applicable like you do when shifting a manual. They are FAR better in truck applications and why they are by far the most popular... I only know cause I've been driving trucks since I was 16 😉 1 of them was a manual and if I would have kept it, it would have found a 400R in it.

I love passin the manual boys with bigger loads even.
 
As a fan of manuals I have to state...


...automatics are inherantly stronger.

Manual transmissions usually have helical gears which have one contact point to transfer the torque, automatics have planetary gears which have three points. This in itself helps immensely, the only currently mass produced planetary manual that I know of is Lenco, and not many street cars have those (though they are easy to spot because the number of levers coming through the floorboard is about that of your average back hoe). Automatics also have the advantage of you can apply torque easily without the vehicle moving, this helps get trailers off the line. The automatic's downsides are the lesser amount of gears, and the torque converter's stall speed doesn't allow for very low speed creeping. I can't knock anyone for getting an auto in a truck nor can I for a manual. They both have thier places.
 
Originally posted by: Triumph
So now I'm wondering, why do 18 wheelers use manual trannies?
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More than likely: Control. When you have 80,000 pounds at your disposal, you'll probably need to utilize different parts of the powerband for diffrent situations. That and engine braking.

Anyone know if jake brakes work with autos?

-PAB
 
Originally posted by: Triumph
So now I'm wondering, why do 18 wheelers use manual trannies?
Click to expand...

I think it's largely to do with the cost and complexity of producing an automatic transmission with enough gears to accomodate that kind of vehicle.

They often have more than a dozen forward gears. Most autos are 3, with 4s being fairly common, and a few really nice ones with 5. No where near the dozen wanted by an 18 wheeler. Autos are expensive...
look at the cost increase from going to a 5 speed manual to a 4 speed auto...now consider that they are trying to cram 15 gears in there...I imagine that the tranny would probably cost more than the truck.

I'm not really up to speed (sorry for the pun 😉) on 18 wheelers, but I understand they sometimes use secondary transmissions to effectively multiply the number of gears coming out of the primary.
Not sure how well that would work with Autos....I'm kinda sketchy on how exactly an auto tranny works.

I'm not an expert on 18 wheelers, it might be that there are some factors I'm missing that make Manuals more attractive on a really big truck than it is on a smaller truck.
 
Originally posted by: Noriaki
Originally posted by: Triumph
So now I'm wondering, why do 18 wheelers use manual trannies?
Click to expand...

I think it's largely to do with the cost and complexity of producing an automatic transmission with enough gears to accomodate that kind of vehicle.

They often have more than a dozen forward gears. Most autos are 3, with 4s being fairly common, and a few really nice ones with 5. No where near the dozen wanted by an 18 wheeler. Autos are expensive...
look at the cost increase from going to a 5 speed manual to a 4 speed auto...now consider that they are trying to cram 15 gears in there...I imagine that the tranny would probably cost more than the truck.

I'm not really up to speed (sorry for the pun 😉) on 18 wheelers, but I understand they sometimes use secondary transmissions to effectively multiply the number of gears coming out of the primary.
Not sure how well that would work with Autos....I'm kinda sketchy on how exactly an auto tranny works.

I'm not an expert on 18 wheelers, it might be that there are some factors I'm missing that make Manuals more attractive on a really big truck than it is on a smaller truck.
Click to expand...

I do believe autos for semis do exist. I think they are under 10 speeds though. PM Tominator. He would know.

-PAB
 
The only auto trans close to the Allison would be the old GM Turbo 400. Best auto EVER made for light-duty trucks and cars.

The best auto O/D(other than Allison) would be the 4L80E GM trans, which is basically a Turbo 400 with O/D and electric valve body.
Ford's E40D's sure aren't very reliable, but have been improved the last few years.

I can't see how any trans, Allison included, would be better than a Turbo 400, regardless of which engine it was behind. Unfortunately for the TH400, most everything is O/D these days.

Allison does make some big, heavy autos for semi's, to answer some questions I saw earlier. I'm sure someone else makes them, too.
 
Originally posted by: PsychoAndy
Originally posted by: Triumph
So now I'm wondering, why do 18 wheelers use manual trannies?
Click to expand...

More than likely: Control. When you have 80,000 pounds at your disposal, you'll probably need to utilize different parts of the powerband for diffrent situations. That and engine braking.

Anyone know if jake brakes work with autos?

-PAB
Click to expand...

Afaik - At my work we have both auto and manual transmission highway coaches. All but one (the oldest bus) have Jake Brakes. However, these buses have max vehicle weights of 15,000-17,000kg, far less than the 40,000+ of a tractor trailer.
 
Originally posted by: SithSolo1
Ok so if I'm at the 78,000 miles on my Ram, I'm about due for a new tranny?
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I hate to say it, but our trans'es suck. I had mine rebuilt at the 8000 mile range under warranty. The next time, it was at my cost because I had done internal and external mods to the engine and upped the power output.

If you are nice to it and do not tow much, then you should be fine. Just change the fluid and all is well.
 
Originally posted by: Noriaki
Originally posted by: Triumph
So now I'm wondering, why do 18 wheelers use manual trannies?
Click to expand...

I'm not really up to speed (sorry for the pun 😉) on 18 wheelers, but I understand they sometimes use secondary transmissions to effectively multiply the number of gears coming out of the primary.
Not sure how well that would work with Autos....I'm kinda sketchy on how exactly an auto tranny works.
Click to expand...

They do effectively have two final drive ratios that you can toggle between. There's a flip switch on the shifter, and when you reach the end of your low gears, you flip the switch. It does some magic back there at the transaxle and you get a different final drive ratio for the higher gears. Much easier than flipping around in a 13 gear pattern. 😉

 
So now I'm wondering, why do 18 wheelers use manual trannies?

My 4 speed 4L60-E DWARFS a 6 speed ZF6 in mass... wonder how big an 18 speed auto would be and how complex it would be at that. 🙂
 
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