My question is how much engine braking can be expected with an automatic transmission in low range first gear. I have a 1998 with a four cylinder engine and manual transmission. It goes down a rocky and steep mountain road in low range first gear at about two miles per hour. This is not according to the speedometer, but according to it taking me an hour and a half to go three miles. The engine keeps the Jeep at that speed, without having to use the brakes. I am considering getting a 2003-2004 TJ with an automatic transmission (with stock breather hose for going through deep water). Will I be able to go down the same steepness at about the same speed without using the brakes in first low? Glad to hear anyone's experience with this. Thanks!
Engine braking with automatic in first low?
- Thread starter DER52
- Start date
I don't think think the auto will engine brake enough to go that slow without brakes. I have to ride my brakes a lot going down steep banks. That being said i'm on 35's with 3:07 gear ratio. Properly geared it may be much better but from my experience manual will always engine brake much more effectively than an auto.
Lots of folks who have followed me down hills have had to get on the brakes to keep up. Gears work both ways.
Those who don't think you get good engine braking with an automatic are those with manual transmissions without experience offroading with an automatic. My TJ has such good engine braking with its automatic and proper axle gearing that if I don't give it a little gas on steep downhill descents, they'll start stacking up behind me. Or they have to ride their brakes. Having an improper axle ratio like 3.07 would reduce the effects of engine braking.
Many thanks to Cornbread, mrblaine, and Jerry Bransford for your replies. Very helpful. Glad to know that low range first gear with an automatic transmission will provide such good engine braking.
You bring up the axle gear ratio. From the post by Chris on Wrangler TJ Stock Specifications, my 1998 four-cylinder with manual transmission apparently has the 4.10/4.11 (I will check tomorrow in the daylight). That may be what is contributing to my present good engine braking. My question, then, is would a stock 2003-2004 TJ with six-cylinder engine and automatic transmission have a sufficiently good axle gear ratio for good engine braking. I am guessing that they usually come with the 3.73, but according to the chart there seems to be some variance in the axle gear ratio. Some may have the 3.07, which you say would not be as good for engine braking.
You bring up the axle gear ratio. From the post by Chris on Wrangler TJ Stock Specifications, my 1998 four-cylinder with manual transmission apparently has the 4.10/4.11 (I will check tomorrow in the daylight). That may be what is contributing to my present good engine braking. My question, then, is would a stock 2003-2004 TJ with six-cylinder engine and automatic transmission have a sufficiently good axle gear ratio for good engine braking. I am guessing that they usually come with the 3.73, but according to the chart there seems to be some variance in the axle gear ratio. Some may have the 3.07, which you say would not be as good for engine braking.
I find it a little disconcerting changing into 4L when actually on a steep decent. Having to put the transmission into neutral so that you can shift from 4H to 4L can be a bit of a pucker factor when you are looking down a steep incline. I always try to be in 4L before I get to the drop off but sometimes you get caught out and just have to hold it on the brakes until you get the shift completed. Anybody got a better procedure for this occasion
Don't start a steep descent or steep ascent if you're not already in 4lo. With a little more experience you'll quickly get the hang of it. My TJ is very rarely in 4Hi, it's usually in either 2wd or 4Low.
I run 4lo the entire time I’m off pavement, honestly thought that was standard practice with the autos
I'm in 4Lo pretty close to 100% of the time I'm off road with the automatic. I always have been, it all started out in my CJ with the 3 speed manual.
Ok I will make 4L my default. Some trails I run can be 100km (60miles) will being in 4L have a significant adverse impact on fuel economy?
Trails are very different for different people in this thread. It really depends on the type of terrain of those trails that dictate what you want to be in. Some, I'm in 4hi all day long. Others are alternating between 4hi and 4lo. Others are 4lo all day.
My 4.0 auto has 3.73 gears and 31" tires. I've found the engine breaking experience using 4L in 1st gear in my jeep similar to what you describe with yours... probably 1.5 -2 mph with no brake applied on fairly steep descents.
There is a video from many years ago of a Blazer coming down Lions Back??? Not sure how automatics work now but the old Turbohydromatics used to only hold low for so long, then sensing no "need" for low from the vacuum, they would up shift. I have never trusted an automatic since then. I sure would not trust any computer controlled transmission.
I an sure there are many angles to story given how old it is. But I've driven many "old" automatics and Ford, Chev, Dodge, they all would up shift independent of the gear you chose.
I an sure there are many angles to story given how old it is. But I've driven many "old" automatics and Ford, Chev, Dodge, they all would up shift independent of the gear you chose.
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If you were around when that happened and popped up on the boards, the story from the folks in the Blazer was it got bumped out of gear and the driver couldn't get it back into gear. Also makes a very good case why folks need brakes that work.
The AW-4 has 1-2 in the same detent position on the shifter. Even it won't shift from 1 to 2 unless it is supposed to. It is oft reported that it is a terrible trans due to that 1-2 thing but we've tested and tested them and they don't upshift and kill you.
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