Engine/Transmission (1994 - 1998) Deisel engine braking power?

[DSutton]

I am considering installing a mystery switch in order to keep the TC locked at certain times. Like when I tap the brake to kill the cruise, and to keep the TC lockup engauged for a little help on downhill runs. my question is, is ther much help braking help from the engine alone to make this a worthwhile consideration? Seems as though I read somewhere on here that our CTD engines don't provide much assistance through engine braking.



I understand all of the other pros and cons on the mystery switch. I am not looking to start another war, or debate the details. I am simply looking for opinions on the switch in these limited circumstances.



Thanks folks

 

[redram]

Lots of braking - it's called 17. 5:1 compression.



Now - whether you can get teh TC to not slip, that's your problem - I have a manual! Hee hee.



Do a search, this has been talked about many times in the past.

 

[Bob Wagner]

a very wise auto transmission guru once told me" brake shoes are alot cheaper than rebuilding a transmission"



the mystery switch will shorten the stock auto transmission lifespan



do it right or be ready to pay

 

[Howard Durand]

There is fair deceleration with just the TC locked up but it is much better with the exhaust brake engaged too.

I never used the "Mystery Switch" until after I had the modified torque converter and valve body installed and the only thing I use it for is braking.

I have read the pros and cons of the "Switch" and try to use it sensibly.

I also made mine so I could keep the TC unlocked.

Under certain conditions this is very helpful.

 

[DSutton]

Howard,



It sounds like you are doing exactly what I would like to do. That is, use the switch for help in braking, not to lcokup at low RPM's and drag. The idea of setting up the switch to not allow lockup seems like it would help also. I have a 3 way switch that would allow 1 Stock operation 2 Locked 3 unlocked.



Eventually an exhaust brrake will be installed, after the ATS transmission and TC.

 

[Howard Durand]

I use the "unlock" position frequently when I am pulling the trailer.

When pulling a big hill in OD and the EGT gets to the point I need to do something, if it looks like I can get on over without dropping into third, I'll unlock the TC. That allows the engine to speed up enough to get the EGT down without having to back off.

There are other times when it is nice to be able to leave it unlocked. The only problem with that is I forget to put the switch back to "normal"

I mounted my switch in the ash tray and included a couple of lights so I can easily tell which position it is in. But I still forget and leave it the wrong position sometimes.

 

[Snow man]

There is very little braking form a diesel,unless there is an exhaust brake. They may have 17. 5 to 1 compression,but as soon as the piston goes past TDC,the energy it took to squeeze the the air,is given back,and it pushes the piston back down. In addition there is no throttle plate on a diesel,so air flow thru the engine is unrestricted. I dont like the freewheeling feeling you get from a stock auto truck when you let off,I have a smart controller on both mine and my Dad's truck. If you run the mystery switch,you need to constantly have a hand on it as you slow down,its easy to forget its on,and it is not good for anything if you come to a stop with it on. Like Bob said,it will cause increased wear,although i fee that without an exhaust brake you wont do any damage to a strong transmission just by using it for braking. The damage is done when you start using it for acceleration,shift locked,come to a stop with it on,or have an exhaust brake.

 

[Doubleclutch]

Snow- Sounds like you are used to driving automatic diesels. NO SLAM! Diesels do get compression braking for the reason you mentioned. When the piston compresses the air charge, heat is developed, some of which is removed by the engine's cooling system. There are also mechanical losses to friction that tend to add braking, both in the engine and transmission. I was surprised at how much compression braking is available because I believed the same as you. Fortunately, I remembered an old proverb- when physical conditions differ with projected, change the formulae.

Greg

PS an exhaust brake works wonders!