Why do Rams and basically every vehicle have the high pitch whine in reverse?

[Davidloveshishemi]

I have heard just about every vehicle backing up have the high pitched whine, I have heard it in every truck I have owned but I never thought to ask why it does that? Does anyone know the science behind it?
Thanks in advance.

 

[OCDTech]

I have heard just about every vehicle backing up have the high pitched whine, I have heard it in every truck I have owned but I never thought to ask why it does that? Does anyone know the science behind it?
Thanks in advance.

From what i read one time, its the angle the gears are cut, not helical, but straight. Helical being at an angle, straight, well straight.

 

[Davidloveshishemi]

So its totally normal? Which is what I thought, like I said, I just didnt know the science of it.

 

[OCDTech]

So its totally normal? Which is what I thought, like I said, I just didnt know the science of it.

Absolutely, weird thing is this was really noticeable in manual transmission vehicles, i never really noticed it in automatics.

 

[Davidloveshishemi]

I have noticed it in both manual and automatic. "Shoulder Shrug" guess its just one of those things.

 

[kurek]

Gears can generally only be set up perfectly with each other on one side of their teeth, and also helical gears are stronger in that drive direction than the opposite. When you put a transmission in reverse you are running at least one mesh on the back side of the gear teeth and they will whine, as will a rear axle for the same reason.

 

[Davidloveshishemi]

Gears can generally only be set up perfectly with each other on one side of their teeth, and also helical gears are stronger in that drive direction than the opposite. When you put a transmission in reverse you are running at least one mesh on the back side of the gear teeth and they will whine, as will a rear axle for the same reason.

Thats why i love this forum, someone seems to always have the answer. I knew it wasnt a big deal, just curious was all.

 

[RAMTRPR]

When you gear these trucks at anything over 4.10’s they whine a bit because of the custom cut to fit the gears. I have 4.56’s and they wine at about 60mph to 70 then it more blends in with my big tires reverse will always whine but I don’t notice it unless I’m backing up at like 20mph (usually in the mud)


Sent from my iPhone using Tapatalk Pro

 

[Davidloveshishemi]

Gears can generally only be set up perfectly with each other on one side of their teeth, and also helical gears are stronger in that drive direction than the opposite. When you put a transmission in reverse you are running at least one mesh on the back side of the gear teeth and they will whine, as will a rear axle for the same reason.

It only whines for a little bit then the faster it goes the whine disappears. Your explanation makes sense though.

 

[88ROOK]

Gears can generally only be set up perfectly with each other on one side of their teeth, and also helical gears are stronger in that drive direction than the opposite. When you put a transmission in reverse you are running at least one mesh on the back side of the gear teeth and they will whine, as will a rear axle for the same reason.

straight cut gears are going to be stronger all around, hence the reason the run them in formula 1 cars, thats where that formula 1 whine comes from

 

[kurek]

Straight cut gears are more energy efficient (good for racing where you want to avoid using horsepower the engine is already making to cook oil instead of going to the road) - this is because the point of contact between meshed gears is minimal and occurs across the shortest distance.

Straight cut can also be stronger in the circumstance that they must work in both directions; but if we work with the assumption that the gears only have to bear load in a single direction if we assume all else is equal a helical gearset can be stronger as the load will be borne to a surface that is arched. You can think of this a bit like how an architectural arch bears weight by delivering the load on a bias to the structure. Helical gears are somewhat like a series of arches folded around a drum and can be quite strong as a result as well as being quiet because the load sweeps them instead of hitting them dead-on. The cost of this is they make more heat and they demand a better lubricant and particularly in bevel applications they can be a whole lot weaker when driven on the back side.

 

[tap4154]

I have heard just about every vehicle backing up have the high pitched whine, I have heard it in every truck I have owned but I never thought to ask why it does that? Does anyone know the science behind it?
Thanks in advance.

Because cars and trucks like to go forward, they don't like to go backward, so they whine when they go backward.

 

[Davidloveshishemi]

I have researched all afternoon, I havent seen where the 8HP70 has any straight gears. They all appear to be helical.

 

[tap4154]

I have researched all afternoon, I havent seen where the 8HP70 has any straight gears. They all appear to be helical.

I suspect the whine is coming from the differential not the transmission. Probably the gears are just cut to be more quiet and efficient going forward, and when the differential goes in reverse they make the whiny noise because they aren't quite as efficient in that direction, and they're also very upset that they're going backward.

 

[OCDTech]

I have researched all afternoon, I havent seen where the 8HP70 has any straight gears. They all appear to be helical.

Straight gears are just one cause of whine, bad bearings, running helical in reverse direction, several other things i imagine can make this noise. I just got back from driving my truck or i would have tried to see if mine does it. I'm sure others may know. If not i will try to check it out Sunday.