Ive got into the habit of kicking the tranny out of OD when coming up to a stop sign to utilize the built in engine braking and save on the regular brakes. I got to wondering today if that might be harmful to the tranny. What do yall think?

 

I have done that for years especially in the BC mountains or on long hills. One must still monitor the RPMs so engine overspeed is not happening.

 

You gotta remember that the E4OD has a locking torque converter that when open can allow for up to 500 rpms of difference between the engine and the transmission speeds, it makes for very poor engine braking. Most factory PCMs will open the converter when you let off the throttle all the way, and you can't really do engine braking with your foot partially on the throttle... Just a heads up, that there won't be no jake-brake like effects from your truck, besides even if you lock the converter the engine will only hold the truck on up to 8%-9% grades in 3rd gear, and this is with 4.10 gears.

 

what we need is a low price way to add an engine brake.-Jake brake.

 

swap in a zf-5 downshift slows me down really fast.

 

Mat, remember my converter is on a switch, hence why my E4OD slows me down just as good as your ZF5 slows you down. I tried going down a 13% grade not too long ago, and I couldn't hold her in 3rd, 2nd did good tho, and oddly enough with the converter open she did better than with it locked.

 

MLSC if your converter is on a switch will it stall the engine if you dont switch it off when coming to a stop? Also will the gearbox still down shift normally when slowing down with the converter locked. If so could you feasably connect a momentary switch that both locked the converter and triggered an exhaust brake so that the coverter performed as designed most of the time but would lock at the same time as the exhaust brake activated when you hit the switch. If the engine stalls with the converter locked then that would sugest there is a solid link between flywheel and diff when locked. If this is the case an exhaust brake would give the extra engine braking required to slow the truck and a momentary switch would mean you could get off the button so the gearbox could downshift once the revs were low enough and get back on the button once you were in a lower gear. If this could work you could almost come to a stop with out using the wheel brakes much the same as we do in our semi's and bigger trucks.

 

ah ok i didnt know you could wire them up to do that. my neighbor blew up he 5.0 e4od downshifting but it was probably ready to go anyway.

I read on here you cant put an exhaust break or anything on these because something with the back pressure and the pre cups. I dont know it would be worth looking into for you guys up in the mountains.

 

All i know is it slows me down without touching the brakes. As long as it doesnt harm my tranny any im gonna keep on doing it.

 

I don't know if it will stall the engine, it should if your engine speed is a bit too low, but considering the possibilities for disaster I'd rather not test it I do know that I once came to a complete stop with the thing locked, but since it was a freeway pull-off I put it in gear before it can stall, and the only thing that made me realized what I did was how the tires were skipping as if I had a nasty wheel hop. And yeah, there is a solid link between the engine and the trans when the converter locks up, but you gotta remember the lockup is accomplished through a clutch setup inside the converter, and as you know the holding capabilities of any auto trans clutch assembly are directly proportional to the line pressure of the fluid fed to the clutch - at standstill idle there's very little line pressure, so the clutch won't hold good and will slip somewhat (not a good thing as it wears it out). Bottom line, you gotta remember to open the converter every time you're shifting into 1st (I personally keep her locked only in 3rd and 4th), and also when you're about to lay on the brakes hard to the point where the rear wheels may lock up - I actually have a relay tied into the BOO switch to open the converter for me every time I step on the brake pedal, that makes for one less thing to worry about. And yeah, you could wire up the converter with an exhaust brake, but it ain't as straight-forward as you may think, actually neither is the manual control switch - you have to feed the PCM a dummy signal when you're overriding its command to the TCC, else it will throw a code on you and may enter failure-management (limp-home) mode. But yeah, with proper downshifting I can come to a complete stop rather well without even using my wheel brakes. Requires knowledge of the TCC and CCS operation tho - I personally start off in 4 lock, then shift into 3 lock (it's an quick open-downshift-lock sequence, but both my switches are on the shifter so easy thing to do), then open the converter and manually shift into 2nd, and finally manually shift into 1st. You gotta downshift manually cause if you don't the coast-clutch won't engage and you won't get the full engine braking you're capable of.

 

I've been reading mixed opinions on that subject - some people claim they have the BD Diesel brake that's specifically designed for the IDIs (keeps backpressure lower so the valves don't float), others say exhaust brakes will kill an IDI faster than anything else... Personally, if I could get a hold of an exhaust brake fpr cheap, I'd be willing to give it a try, after making sure it runs proper exhaust backpressure of course.

 

This summer i had my vaccum pump go out on me on the interstate outside of omaha, on my way to minnesota (450 miles) and had no real choice but to downshift to slow down the whole way with a boat behind me and it didn't seem to hurt it at all. I'd be willing to try a BD Diesel Brake if they made it for my truck for sure.

 

Oh, but they do: BD Diesel Performance Exhaust Brake - Ford 1983-1994 6.9L/7.3L IDI w/3.0" Exh

 

The reason it worked better unlocked is that the torque converter acts as another gear reduction, about 1.7:1 or so.

 

Are you sure? Cause in 3rd and 4th if I open it I get squat for engine braking, and it makes sense cause the trans is allowed to freewheel at speed quite higher than the engine speed, whereas when I lock the converter it forces the engine to spin much much faster than it wants to and increases engine braking. In 2nd I'd think the same thing happens, but I guess not...