Mountain Driving with the 4EOD - Diesel Forum

City Cruzer · 12-23-2012, 08:13 PM

I have a question about driving my truck on winding mountain roads, more like twisty roads where the speed limit is ~45 mph.

I've tried leaving the TC locked, driving in second, etc., but just can't find the right combination. When the TC is locked, it does absolutely the exact wrong thing at the wrong time. When I approach a turn with it locked it feels just about perfect but once the speed drops below 35 or if I tap my brakes, it disengages and seems to put the truck in what feels like neutral with no useful BHP. This forces me to use the brakes even more which is dangerous on a wet or slick mountain road with a heavy truck.

I've tried driving in second and it seems to do the same. There is never enough BHP to hold the truck in a turn. However, when I'm in a straight or long straight decent, it's fine because there is no need to slow below 35 or tap the brakes. Also, it seems like second won't engage unless I step on the accelerator.. again dangerous in certain conditions.

Any suggestions how I can get reliable BHP that will hold the truck on decents in mountain roads and stay on? It's a bit annoying traveling Angeles Crest Highway for example where the speed limit is 35 to 50 MPH, heavily traveled, lots of tight twisting descents on slick, and sometimes snowey or icy roads.

RonKZ650 · 12-24-2012, 08:45 PM

Having the automatic is good as being in neutral on down grades. The facts of life and the wonders of the automatic.

**Mark Kovalsky** · 12-24-2012, 09:17 PM

Only if your automatic isn't working right. I've driven an F-550 at 30,000 pounds combined weight down some very steep grades and used the engine and transmission to maintain a safe speed.

I'm assuming the BHP means braking horsepower. BHP has always meant brake horsepower to me, or how much power the engine makes.

If you are below about 40 MPH and don't have the OD OFF light illuminated you will not have any engine braking. If you turn off the OD (light illuminated) you will have engine braking.

If the torque converter is unlocked you will have 10% less engine braking than if it is locked. If there is no engine braking then there is something wrong with the coast clutch. Usually it's the snap ring that holds it together, it can come out of the groove and then the clutch won't engage.

mojoman · 12-24-2012, 10:19 PM

I live in the interior of BC....lots of mountains here...I idle down the hills in 2nd....never a prob...maybe your tranny needs attention???

Stan96 · 12-24-2012, 10:47 PM

I used to allow the tranny and engine do as much deceleration as possible untill a light went off over my head and i figured out that brakes are much less expensive to replace than a tranny, so now when the tranny downshifts, then i apply the brakes more. I know what you mean tho, that 41 mph area is rough, either the motors goin over 2 grand in third or in OD it's down around 1300 and lugging. If ya got in in 4x4 all the brakes are acting the same so that might be safer, I keep about 600 lbs of firewood in the back of mine. (3:55 gears)

okie1 · 12-25-2012, 08:13 AM

There is nothing wrong with your transmission, when you hit the brakes it unlocks the torque converter which basically leaves you with zero engine braking.

**Mark Kovalsky** · 12-25-2012, 08:30 AM

That's completely wrong! The transmission HAS engine braking with or without the torque converter locked. There is 10% more engine braking with the converter locked, but there is engine braking either way.

City Cruzer · 12-25-2012, 01:56 PM

Thanks for all of the replies and Merry Christmas!

I think Mark has it right. I think the coast clutch might be the problem because I've let the truck coast on a downgrade and it will keep gaining speed as if it is in neutral. Then if i give it will a slight touch on the gas pedal, it will engage the tranny and there is plenty of braking horsepower with the OD light off. Doesn't seem right. It disengages again if the brake is applied.

This is about about a 3 year old transmission but i will have it looked at

chuckster57 · 12-25-2012, 02:20 PM

Quote:

Originally Posted by RonKZ650

Having the automatic is good as being in neutral on down grades. The facts of life and the wonders of the automatic.

I have come down some steep grades with 10,000+ lbs of trailer hooked on, and I can assure you that it has been NOTHING like being in neutral. Twain Harte grade is a good example, I was able to maintain 35 MPH and stop safely at the bottom without having to heat up my brakes. If I were to take it in neutral, I would have easily started the grade @25 MPH and been over 100 MPH at the bottom.

RonKZ650 · 12-25-2012, 05:15 PM

Well it's not like being in neutral, I was a little bit exaggerating there, however look at your tach. If you are going down a grade at 3000 RPM, tap the brakes. The revs drop to about 2500, so you lost a lot of engine braking. Good as being in neutral to me. Normal operation. Not horrible, just normal operation. If I had my way they would not even allow automatics to be sold. All vehicals should be manual, but I don't have my way. One really good thing came out of it as Ford no longer offers a manual, Chevy doesn't offer a manual, so those two lines are never on my buy list ever again for 100 years unless they change their mind. I save money big time by never buying a new truck again.

MichaelPatrick · 12-30-2012, 10:42 AM

I installed a switch on my torque converter to manually lock it up on downgrades, even when the brakes are applied. However, I have to be careful to unlock the TC when speeds get too low to prevent damage. I have a red light on the switch to show when the TC is manually locked, and use a protected switch to assure it is not activated accidently.

I also installed a protected switch and red light to manually activate the EBPV to allow exhaust restriction braking on downgrades, which also is very useful when towing a heavy load.