Down shifting to slow down

[Wing Nut OOA]

Just wondering if anyone else with a 6.5 does this,

I have an auto trans and when i'm coming to a stop, at about 35mph I pull it down into first and the rpm goes up to about 2800 and sounds like I have a jake brake,

I dont see how this could be harming anything but does anyone else have thoughts?

[Edahall]

Just wondering if anyone else with a 6.5 does this,

I have an auto trans and when i'm coming to a stop, at about 35mph I pull it down into first and the rpm goes up to about 2800 and sounds like I have a jake brake,

I dont see how this could be harming anything but does anyone else have thoughts?


I would not do this. Automatic transmissions are made to shift under load. I would just use the brakes to slow down. That's what they're for. New brake pads cost a lot less money than a transmission rebuild.

[arveetek]

Just wondering if anyone else with a 6.5 does this,

I have an auto trans and when i'm coming to a stop, at about 35mph I pull it down into first and the rpm goes up to about 2800 and sounds like I have a jake brake,

I dont see how this could be harming anything but does anyone else have thoughts?


I do the same thing when towing a trailer. It may be harder on the transmission, but I see it as a safety issue more than anything. Assisting the brakes is always a good idea. I would hate to overheat the brakes and compromise safety.

I don't see the point in doing this when not towing or hauling a heavy load, however.

Casey

[rustyk]

I had the 4L80E rebuilt to much higher capacity, and had the TC replaced with a Sun Coast Converters brazed unit. The tech said using the tranny to brake was not at all a problem.

Whether this advice would hold for a stock drivetrain, I don't know, but this one's in an 8T motorhome.

[DmaxMaverick]

Automatic transmissions are designed for compression braking. I don't know of ANY issues because of it, abuse notwithstanding. All modern transmissions (modern = the last 40-55 years, depending on mfg and model years) were modified to accommodate grade braking ("coast" sprag). If you break one by braking, it was already broke.

[gimpyhauler]

Hate to say this but the first thought this tired old man thought of is that you need to buy a modern truck. :D That was written with a smile.

However, that is exactly what my '07 GMC 2500HD does automatically going down long steep grades when I'm towing.

Doing it manually as you want to do seems like to much thought and work to me. Gotta reserve my limited energy so I can still open my social security check. :rolleyes:

[richp]

Hi,

I confess. I let my Allison do the braking for me and my 12,000 pound fiver all the time. Always thought that's exactly what they were designed to do...

And after more than a quarter of a million miles between two trucks -- towing about half those miles -- the trannies never have so much as hiccoughed.

FWIW.

[SoTxPollock]

Hope things are going well for you in Nashville, I'm a picker, but I'm staying in Texas, been playing here since I was 13 and Ain't it Great!!
Gearing down as you are doing will of course cause some wear on the transmission, because it has to dissipate all of that energy built up by your vehicle and whatever it's towing or hauling, but I wouldn't worry about it. Doing it manually I'd suggest you punch the throttle as you are pulling it down to the low gear. That will take some strain off the transmission, actually since you know it's going to go to 2800 rpm's try taking it up to N and bringing the rpm up to 2800 and popping it down to low, bet it will be a much smoother downshift. Just don't try that on an Allison, it's computer gets confused if you are going forward and shift to neutural. Most automatics won't allow the transmission to downshift until the vehicle slows to a certain speed to keep it within the rpm range of the engine, it's a safety thing just in case you or someone in the vehicle accidently hits the shift lever and puts it into Low while you traveling at say 70 mph, it's not going to downshift.
If you just pull it down to low, I'd suggest at minimun to be accelerating hard enough just for that brief moment to let the engine reach the required rpm without the suddend load up that you experience by just downshifting the transmission without your foot on the accelerator. If you want it to last a long time, try not to be too rough on it.
Ditto on the new truck idea, when you make that first big pile of money from your music, I just bet that will be at the top of your list. Sounds like material to write a song about.

[Wing Nut OOA]

Oh sorry, fyi I was on my way back top oregon when I posted this, total weight was about 13,5000

I dont really see a point empty but I can stick it in 2nd and comfortably go down a pass at about 40-45mph

This however was nothing near our excitement

Here is what I sent all our friends

Ok here's the details from the last couple days of our trip home: friday morning after 4 hours of driving the alternator in the truck seized up and caught fire, 20° outside in tonopah nevada, drove the jeep 2 hours to bishop california to the closest parts store, headed back, and spent 3 hours installing parts and trying to get the truck jump started after sitting in the cold for 11 hours. Hit the road at about 8pm, drove 2 hours slept for 3, started yesterday morning at 1am and drove till we were just outside of oakridge OR, coming down the hwy 58 pass, the tow bar broke loose from the jeep and it started to move into the oncoming lane, I slowed the truck into the jeep and eased it to the side, tried to just drive the remaining 2 hours but somehow the jeep broke an axle shaft, call my brother and he brings a trailer, load the jeep on, start the truck and it starts screaming like a banshee, the starter was going out and the a/c pump was fried and seized solid. At that point we unloaded the jeep, limped it into oakridge for the night and used the trailer to get the truck home, went back this morning for the jeep, we are home, truck is already fixed, glad to be out of the woods. been a very stressful last month and a half!

[DennisG01]

..........

[DennisG01]

That post above is me "speechless". What a wonderously eventful trip you had!

Glad you made it back safely.... Eventually, that is.

[DmaxMaverick]

..........

Ditto. What an ordeal. I've had bad days, but......

[SoTxPollock]

That's some pretty amazing driving to be able to see the jeep break loose and have the presence of mind to get in front of it with the truck and slow it to a stop without tearing up anything big time. I once lost my jeep from the back of the truck and watched it pass me up on a two lane highway, my thought was boy it sure looks good right now but how's it going to look in a couple of minutes. it did a slow bend to the left onto the shoulder and then off into the grass where the tow bar tongue dropped down and started skidding in the dirt until if came to a stop, didn't hurt a think. I just left it sitting there and went on to the deer hunting spot and after the morning hunt, I came back and hooked onto it and took it back home realizing I had used the wrong size ball on the truck to hook to. I can still see that jeep passing me in my mind and I bet you can still visualize all that which happened to you. Glad to hear you made it back uninjured. What do you think caused all that to happen, man you talk about song writing material, you definately have some there, I'd suggest you tell those stories in a few recorded songs and let the music play on.

[argo]

If you have a TH-400 or a 4L80-E I wouldn't worry, or an Allison for that matter. If you have a 700-R4/4L60/4L60E however, I would not do this. The tiny clutch they use to provide engine braking is not meant for this type of use on a regular basis. It is made up of two friction discs that are about 4 inches in diameter. I would suggest that if you have the 700 or any of it's family, then you save that for an emergency.