4 Wheeling forward in reverse gear? (1 Viewer)

[Big Red 64]

While I was waiting in line to vote yesterday I got into a conversation with a couple of guys about transmissions. They claim that it is common practice with automatic transmissions to put it in reverse while going forward down a steep slope and using the engine to brake. Is this true? Sounds like a good way to trash the tranny to me. I've always had manual transmissions (FJ 40 and 60) and have just bought my first 80 so not much experience wheeling with an AT. Anyone tried this technique or heard of doing it?

 

[KliersLC]

Maybe with a jeep tranny, I suppose that it is possible for a tranny to slip enough to allow this, but you are correct, it will trash your tranny.......

Dan

 

[MLX450]

Hummmmmmm......... Why not just put it in a lower gear? Reverse - i don't think so........

 

[alkaline747trio]

I think they were yankin your chain...bad idea.

 

[RavenTai]

At minimum the slipping torque converter is going to make a lot of heat, AT's that experience a lot of heat do not live long, at worst it will break something,

brake pads are much cheaper in comparison.

 

[cruiserdan]

That is a quick way to get a new transmission.

 

[homchz]

I don't even know of a "good" auto tranny that will go into reverse while moving forward.

 

[kiwidog]

Guys, you can certainly use the trans in reverse going down hill and using the engine for braking. ( you have add engine speed to slow down which is hard to get you brain around but just think about it for a minute and it will make sense) This won't hurt the trans. any more than going forward with the trans in forward

Just imagine you are sliding down a slope and trying to back up at the same time. the automatic wil take this no problem a long as you don't over heat it. There is no mechanical connection ( its all done with fluid) between the input shaft of the transmission and the engine other than when you are in lockup mode but this mode does not come on in reverse Although with enough thought/study of the transmission circuits you could probable over ride this function and have lockup in all gears including reverse.
I have done this with TH 350 lockup transmissions over 20 years ago. Haven't looked at one for a long time so would have to think about how to do it again.
The lockup clutch in the torque coverter is not really designed to take the added torque of the push back through the transmission, however it does work.

If I remember correctly someone used to make a torque convertor with a sprage clutch( one way roller clutch) built into the input turbine that locked the input shaft to the engine so you had full engine braking when you where off the throttle. Normal function on the throttle.

So don't be scared of putting the automatic transmission in reverse while going down a steep slope. Along with the brakes and the gas pedal you have more braking. You just have to train you brain.
You should be going slow or near stopped before you put the trans in reverse. Some trans, have an over ride so you can;'t do it at speed.

Try it you'll like the results. just be careful not to get it too hot, although the stock trans, cooler is designed to take alot of heat.

Thanks jb

 

[LandyLover]

If you had a 100% or even 50% grade, even a short one, how would you know how much heat you are forcing the trans to take? You dont know. Its quite a gamble.

I still dont know what advantage there is to doing this. This thought is akin to doing a brakestand but without the wheels spinning. Jump on the brake and the gas and you get heat. Jump on the gas while the trans is in reverse and you are moving forward down a hill, you get heat.

Pads are cheap, using low gear in low range with the CDL engaged is cheapest.

However, I'd love to see someone in their 80 go down a 100% grade in a local gravel pit a few times to prove me wrong!

Cheers

 

[IdahoDoug]

I realize that you CAN do this and simply dump a bunch of heat into the transmission's torque converter and everything else in the tranny. But why risk it versus simply using the brakes? Slowing a 5300lb 80 series on a given slope takes X amount of heat. Whether you're using the brakes, or the tranny, what you are doing any time you slow an object is converting its inertia into heat. That's fundamental and unchangeable physics - brakes convert movement of the truck into heat via friction and that's what stops you. After a 100 yard steep hill, jump out and spit on any disc rotor. The resulting sizzle will give you an idea how much heat it took to control your truck's speed on that hill. Then ask yourself if you'd rather put that heat into an automatic transmission that costs thousands to repair if you overheat it, or into 2 ventilated disc brakes and 2 solid rotor brakes designed to handle repeated panic stops from 60mph?

Don't do it. In no dim dark corner of the automotive engineering world would you find a trained engineer that would agree this is preferable to using the brakes.

DougM

 

[KliersLC]

Slowing a 5300lb 80 series on a given slope takes X amount of heat. Whether you're using the brakes, or the tranny, what you are doing any time you slow an object is converting its inertia into heat.

DougM

On a further note, it would actually take more heat using the Tranny due to the engine and TC trying to turn it the other way. If you just had friction in a tranny, For instance, a downshift, then your heat values would be close to equal, but with the engine turning the input shaft one way, and the drivelines turning the output shaft the other way, you have twice as much slippage wherever they meet.

And that makes more heat than I am comfortable subjecting even my bus tranny to......

Which reminds me, I doubt toyota designed its busses to go forward while in reverse.......

So it would follow that the 80 is not designed for it either, regardless of the size or efficiency of the tranny cooler......

Dan

 

[LandyLover]

Its wrong to run forward in R. But the real question is, WHAT is the perceived value to doing this? And how do you get talking about this in line at a federal election?

 

[CJF]

I honestly think you guys are being closed minded about this.

For example, think about slowly climbing a steep incline in 4Lo, 1st gear. There's really not much less tranny/torque converter slippage in that situation (maybe even more) than if you let off the gas, stayed off the brakes, and let the rig slowly roll backwards down the hill.

I'm NOT recommending doing this (plus, I think our rigs will shut off as a safety feature if you try it?), but I'm pretty sure it is/was a standard method way back when.

Curtis

 

[Big Red 64]

It was a 40 minute wait in line to vote. The 2 guys behind me were talking about their trucks and one said that he really missed the low granny gear in his automatic tranny when descending the pitches in Moab. The other guy- probably 60-65 years old- started talking about using reverse to crawl down. I had never heard of this and jumped in on the conversation. I don't think I will try it even if it does work. Can I expect that the AT in the 80 will not engine brake as well as my stock 76 FJ40- both in lowest gear?

 

[Arya Ebrahimi]

I think you can do it in a manual. My uncle did it in my other uncle's car D) when I was younger and nothing abnormal happened.

 

[KliersLC]

I think you can do it in a manual. My uncle did it in my other uncle's car D) when I was younger and nothing abnormal happened.

How does that work without toasting the clutch or scrubbing the tires?

 

[GXO]

People like this voting is why the country is screwed up

 

[-Spike-]

Using forward gears in low range produces enough braking to keep me off the brakes in all but the most extreme situations. I wouldn't want to be playing with the tranny and gas pedal in those extreme situations- I'll just use the brakes.

I've had my 80 in reverse going forward, drifting back down a small hill that I had just reversed up. The engine stalled almost immediately when it got moving like maybe 3 MPH. Giving it gas in that situation, it will just go backwards. The whole idea seems pretty stupid to me.

-Spike

 

[Arya Ebrahimi]

How does that work without toasting the clutch or scrubbing the tires?

Beats me, I was like 12 at the time, maybe he was just f-ing w/ me?

 

[landtank]

The other guy- probably 60-65 years old-

There you go, the guy was probably driving a car with drums on all fours and the tranny trick was better than the alternative which would be loss of control.

Systems now a days are much better, especially the brakes.