Well I know when IM in Moab and I come to a steep as shit decline, I slam it in first gear, my RPMS go sky hihg, and then I slam on my NICE SEXY hydraboost brakes for COMFORT!
D90 Downhill Woes
- Thread starter Cambo
- Start date
I haven't talked in depth with my buddy yet, but found out he has 4.10's and 35's. Also, he mentioned before the RPM's were all the way up, I imagine at about 4-5K. I definitely need to jump in his truck and get a feel for what he is talking about. The Rave list looks like a good place to start though.
Cambo said:
sounds like he is doing steep enough terain that the engine alone wont slow him down to the safe speed he wants. He just needs to use the brakes and control the speed . sounds like his truck is working correctly and he is just in the same spot the rest of us are because we have auto rovers.
I agree with the additional information it is a fair assumption that the truck is behaving properly and driving style will need to be adjusted for the terrain.
Post the write up, I would like to read it as well.
It is always a bit scary going down really steep inclines with rover brakes being the only thing keeping you from flying off into space.
Post the write up, I would like to read it as well.
It is always a bit scary going down really steep inclines with rover brakes being the only thing keeping you from flying off into space.
Ok, back to the problem at hand. I got an email from my buddy, here is his response:
Now the question is: Is the truck performing correctly or should the engine at least be holding me back. Went down a steep grade. OK steep by anybody?s standards, (east or west coast) but not a ski slope. Maybe 20-25 degrees. 4WL, auto set to 1, no throttle. 15+ mph, enough to get airborne on some bumps. There is no coming up to speed. I don?t feel any ?engine braking?. It?s more like a free fall and constant acceleration. Tried again in 2nd and went much faster, 3rd faster yet, Drive ?ludicrous speed?. So, the transmission appears to be working. Not shifting up to D without me knowing. The thought is, when the PO swapped out the manual to an auto, did he miss something.
Now the question is: Is the truck performing correctly or should the engine at least be holding me back. Went down a steep grade. OK steep by anybody?s standards, (east or west coast) but not a ski slope. Maybe 20-25 degrees. 4WL, auto set to 1, no throttle. 15+ mph, enough to get airborne on some bumps. There is no coming up to speed. I don?t feel any ?engine braking?. It?s more like a free fall and constant acceleration. Tried again in 2nd and went much faster, 3rd faster yet, Drive ?ludicrous speed?. So, the transmission appears to be working. Not shifting up to D without me knowing. The thought is, when the PO swapped out the manual to an auto, did he miss something.
15+ sounds too fast for that grade to me if he is in low gear in the transmission and transfer case, Musky what's your opinion?
well it sounds like the engine is doing some braking because it goes faster in higher gears. but like I said from the start these auto's really dont provide much engine braking.
this is really a tough thing to diagnose further over the internet. If I had the truck to drive I could tell in a instant if its acting strange.
there are a number of things that play into engine braking. Idle speed is one but another that people dont think much about is how fresh the engine is. If his engine has a ton of miles on it and the compression has dropped alot the truck can also really loose alot of engine braking as well.
this is really a tough thing to diagnose further over the internet. If I had the truck to drive I could tell in a instant if its acting strange.
there are a number of things that play into engine braking. Idle speed is one but another that people dont think much about is how fresh the engine is. If his engine has a ton of miles on it and the compression has dropped alot the truck can also really loose alot of engine braking as well.
You have to hand it to the guy for testing all of the options. I don't think I would have tried any higher gears if I was getting air in first low!
MUSKYMAN said:
X2 I had said the same thing in a earlier post only not as well a Thom put it...[shitty engine]
I think a compression test might help take the issue further.
I have to say it sounds a little fast.
SYMPTOM 21 - ?1? Selected 1st gear no engine
braking
FAULT - Clutch brake 3
SYMPTOM 22 - ?2? Selected 2nd gear no engine
braking
FAULT - Clutch brake 1
doesn't really sound like the issue fits these... as he is getting some...
According to the calculator if the D90 is in fact doing 15+ mph in first low then the engine rpms on 33" tires would be 4856 rpms.
I think something is wrong somewhere, my truck(s) would blow up if it turned 5k rpms.
Could it be a bad torque convertor?
I think something is wrong somewhere, my truck(s) would blow up if it turned 5k rpms.
Could it be a bad torque convertor?
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MUSKYMAN said:oh hey and just to make sure there isnt misinformation in this thread.
your lower gears make your truck go slower not faster
a truck with stock gears does not have as low a crawl ratio and low is slow
just to be clear
Scott's running 35's so the geareng is offset by the tire diameter-still taller than stock. His truck is beadlocked,threelinked,and difflocked-seen him do plenty of 45%+ downangle stuff
Doug C said:
well sounds likie my internet assumtion is right then...It sounds like to me he is just wheeling stuff that is past the engine braking of these autos.
he's not alone.
why would a 4.2 or a 3.9 'blow up' at 4500 rpms??? do explain, not that it sounds good or anything, but I can rev my rig in 1st at 4500 rpms with out fear of thermonuclear explosions
Cause the 4.2 has 206,000 miles on it and I am a chicken when it comes to revving an old engine that high.
The 3.9 could take it but as I indicated, I am a whimp, I don't like to go much over 3k rpms in normal driving.
See Musky's pictures in the general section!
The 3.9 could take it but as I indicated, I am a whimp, I don't like to go much over 3k rpms in normal driving.
See Musky's pictures in the general section!
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