coasting

[flair1111]

Just let it do what it was made to do and quit trying to "beat the system"

in an auto yes, in a stick...no.

 

[J-Thompson]

in an auto yes, in a stick...no.

how so?
I know that if I am doing 70 in the KJ and let my foot off the gas the RPM does not fall to idle but stays at about 2200 until it slows to about 40 the engine holds it back just like a stick
and the 3 speed TF999 in my TJ you can feel it slowing more than a stick if you let off the gas 3000 RPM at 70
in fact with the detroit in the rear and the cruise on if I tap the break it will pull due to the loss of applied power but the fact that the engine is holding the rig

neither a stick or an auto will burn any more fuel at idle or at 3000 rpm down hill if you are not touching the gas
I know that the KJ said we were getting 99.9 MPG going down hill in the Smokies coming down from New Found Gap in second gear doing 2500 or so RPM and it did this for about 8 or 10 miles

 

[JeepJeepster]

The engine breaking in my kj is no where near as good as the zj I use to drive. It seems like the 3.7 gives it some gas and lets the rpms go up. With the 4.0 the jeep stayed at a certain speed and the engine rpms never moved.

I shifted mine into N the other day just to see what it was like coasting down a hill. Odd thing I noticed was the rpms stayed around 2,200 even though I was rolling at 60mph with the ****** was in N. It never did go back down still I put it back into gear.

 

[ms5490renegade]

how so?
I know that if I am doing 70 in the KJ and let my foot off the gas the RPM does not fall to idle but stays at about 2200 until it slows to about 40 the engine holds it back just like a stick
and the 3 speed TF999 in my TJ you can feel it slowing more than a stick if you let off the gas 3000 RPM at 70
in fact with the detroit in the rear and the cruise on if I tap the break it will pull due to the loss of applied power but the fact that the engine is holding the rig

neither a stick or an auto will burn any more fuel at idle or at 3000 rpm down hill if you are not touching the gas
I know that the KJ said we were getting 99.9 MPG going down hill in the Smokies coming down from New Found Gap in second gear doing 2500 or so RPM and it did this for about 8 or 10 miles

mine drops to 650 rpms when i coast.

 

[Ry' N Jen]

Just leave the vehicle in gear, weather it be a manual or an automatic transmission. Less chance of something going bank and leaving you at the side of the road.
And for those who want better fuel economy? Buy something other than a 4X4. Or walk to the corner store instead of driving the 400 meters.

 

[flair1111]

how so?
I know that if I am doing 70 in the KJ and let my foot off the gas the RPM does not fall to idle but stays at about 2200 until it slows to about 40 the engine holds it back just like a stick
and the 3 speed TF999 in my TJ you can feel it slowing more than a stick if you let off the gas 3000 RPM at 70
in fact with the detroit in the rear and the cruise on if I tap the break it will pull due to the loss of applied power but the fact that the engine is holding the rig

neither a stick or an auto will burn any more fuel at idle or at 3000 rpm down hill if you are not touching the gas
I know that the KJ said we were getting 99.9 MPG going down hill in the Smokies coming down from New Found Gap in second gear doing 2500 or so RPM and it did this for about 8 or 10 miles

In the kj either way would probably be almost no differencr in overdrive vs neutral, i was talking about my truck mostly there. See, i was just wondering why an auto would be hurt by coasting then shifting back into gear while still going pretty fast is all, KJ or anything else for that matter. but in my truck i have no power anything to worry about so i can just throw it in N and cut the engine off and coast 1-2 miles at a time going to and from work. it really adds up...and plus its a 3 speed only so anything over 40mph in 3rd slows momentum alot so N is way better in the old truck and it has a 3.05 rear gear. i do however see your point for the KJ, but trust me in my old truck 3rd with no gas applied will slow me down alot. I can go 50 down some hills with idle only vs 65 or better with N and engine off. Again the original question was just an overall wondering as to why autos take a beating when shifting back to D after coasting while still moving ...not so much as i was going to do it in the KJ. I knew that in the KJ it was pretty much pointless to do it anyway as the rpms in 4th didnt hold the rig back unless you were going faster than say 70. i just hope the starter on the old truck holds up to being turned over 7 times each way vs once. surely it will, even then a new starter is only about $16 for it anyhow. either way ive went from 6 trips to work and home on 10 gallons vs 17 trips on the same 10 gallons coasting in N. hope that makes sense..

 

[flair1111]

The engine breaking in my kj is no where near as good as the zj I use to drive. It seems like the 3.7 gives it some gas and lets the rpms go up. With the 4.0 the jeep stayed at a certain speed and the engine rpms never moved.

I shifted mine into N the other day just to see what it was like coasting down a hill. Odd thing I noticed was the rpms stayed around 2,200 even though I was rolling at 60mph with the ****** was in N. It never did go back down still I put it back into gear.

Really? Thats seems very odd and not right. I wonder whats going on there.

 

[tjkj2002]

flair1111Quote:
Originally Posted by JeepJeepster
The engine breaking in my kj is no where near as good as the zj I use to drive. It seems like the 3.7 gives it some gas and lets the rpms go up. With the 4.0 the jeep stayed at a certain speed and the engine rpms never moved.

I shifted mine into N the other day just to see what it was like coasting down a hill. Odd thing I noticed was the rpms stayed around 2,200 even though I was rolling at 60mph with the ****** was in N. It never did go back down still I put it back into gear.

Really? Thats seems very odd and not right. I wonder whats going on there.

That would be the 42RLE ****** at fault,the the TC is unlocking.My KJ has great engine braking,but I have the better ****** with the better programming,which plays a big role in engine braking.If I put it in 3rd gear on a down hill(highway speeds)it will keep my speed and actually slow me down,plus I get a real nice grumble from from my Thrush muffler.

Now in 4low it still has good engine braking as long as the rpm's stay under 1000rpm's,my weight is to much on those really steep downgrades to keep the engine rpm's under 1000,plus my brakes suck with being so overweight but that all will change with the 4.3:1 low in my new t-case and 5.13 gears in my new diffs.