Exhaust brakes not needed with auto transmissions?

[klenger]

See post on rv.net.

Hey gang. . the reason no exhaust is approved for the automatics is due to heat via torque convertor slippage. . But here is the skinny... An EB is not needed on the auto... They hold the load back when decending long grades... The manuals, however don't...

Can someone explain how an automatic transmission can provide better engine braking performance than a manual transmission?



I keep reading similar post from the Chevy D/A owners who claim that the Allison does not need an exhaust brake becuase it has "grade braking".

 

[jwduke]

klenger, Id like an answer to that question too... . We towed our 5ver over Arbuckle Hill (Long hill on I35 N of Ardmore,OK) and on the down hill side, I had to keep applying brake pressure to keep the speed down.

 

[dresslered]

Not to worry Klenger, that is just an urban legend.

 

[HBarlow]

Not to worry Klenger, that is just an urban legend.

In the same category as "Ford owns Cummings(spelling error intended)".



Harvey

 

[NIsaacs]

My guess is, the guy bad mouthing the manual transmission's hold back power, bailed off the mountain in 6th gear and waited for the tow/haul or automatic down shift to take place. When it didn't, he figured the maunual was no good!! That was a funny post over there, "gosh" Klenger, don'tcha know better that to stir up some people's kids, and you a senior member and all, thats too funny!!





"NICK"

 

[CPG]

Have a friend with a 04. 5 with the six speed. He has a exhaust brake on it.

Way more control going down hill with his big fiver than I do with the 48RE. and our lighter trailer.

The Tow/Haul feature on mine only takes it out of OD. The loc/up converter only locs up when its ready or in 2nd gear. Sure wish that D/C would get on the band wagon for the RV folks. This 48RE IS a huge difference between the old 518 with the OD in my old "93" CTD though.

Living in this area, and the constant traffic & shifting has kept us with the auto. The manual shift has more control. Clutch versas T/C. In my opinion the Clutch wins out.

 

[Smarshall]

Didn't Work For Me

:--) I've had a manual with an exhaust brake and I now have an auto which I just put an exhaust brake on for our trip to Alaska. Without the lock-up for the torqure converter, it's a waste of money. With the torque converter lock-up, it's worth every penny. I went as far as to put a 2nd gear lock-up valve body in my auto to improve engine braking. To keep the torque converter locked on a stock auto you have to keep your accelerator almost to the speed you're going to keep it from unlocking.

 

[OTRPU]

Some reason I didn't have to do this. But I've taken my TransCommander off since the PAC Brake took out my Input shaft. Lost it on the downhill tween Cheyenne & Laramie, WY. Don't know bout others but now I'm for brakes are cheaper than trannies, and I do it everyday.



Cheers,

Steve J

 

[Joe G.]

To keep the torque converter locked on a stock auto you have to keep your accelerator almost to the speed you're going to keep it from unlocking.

You can make some mods to the TPS circuit and keep it locked above a certain speed even with a stock TC.

 

[Bill Stockard]

I went as far as to put a 2nd gear lock-up valve body in my auto to improve engine braking.

The torque converter in my '03 HO/48RE locks up in 2nd gear if I manually shift it to 2nd gear. The torque converter stays locked in 2nd, 3rd, and 4th at engine speeds above about 1800 RPM. I downshift to keep the RPM above 1800 to utilize engine braking.



I returned from a trip to Colorado "high country" last month and the truck did great coming down steep grades using only engine braking. However, I don't tow, only haul at slightly above the GVWR.



Bill

 

[Steve St.Laurent]

When I test drove a D/A for comparison purposes I was VERY impressed with the grade braking of the Allison auto. It provided about the same level of braking as a PAC brake on a manual Dodge. It wasn't as strong as the BD brake I have on my truck however. So what they are saying is in part true.

 

[klenger]

I am still at a loss to understand how an automatic transmission can do anything to improved engine braking other than to automatically downshift and lock up the TC. How can that be anymore effective than manually downshifting and letting the clutch out?



From your comments Steve, and my understanding of diesel engine braking, I would have to assume that the DuraMax engine has more inherent braking ability than the CTD, and would also assume that a manual transmission equipped DuraMax would perform the same as an Allison.



Someone please educate me.

 

[Steve St.Laurent]

According to this http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11#82 it just downshifts automatically (and I would assume remains in lockup). It can downshift all the way to 1st which you couldn't do by manually selecting gears in the dodge. It sure felt like more than that to me.

 

[Bob4x4]

My 05 48re does downshift and hold lock-up going down grades,but I dont think it will be enough with a trailer in tow. I haven't had a chance to hook up the trailer yet.



Bob

 

[Sarge]

WHOA! HOLD THE PHONE!! DID YOU SAY "MY" 05' 48RE?? Bob, what did you do!?!?

 

[klenger]

According to this http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11#82 it just downshifts automatically (and I would assume remains in lockup). It can downshift all the way to 1st which you couldn't do by manually selecting gears in the dodge. It sure felt like more than that to me.

I can. Oo.

 

[Bob4x4]

That's right Sarge... ... ..... I broke down and modernized The ol 94 is going to stick around too.



Bob

 

[Sarge]

So give up some details... ... . color, equipment ect... ... ...

 

[Bob4x4]

So give up some details... ... . color, equipment ect... ... ...

Atlantic blue,long bed, 4. 10's sunroof,KORE race suspension,everything but GPS,u connect,seat heaters and electric transfer case. Had to have the cubby for the gauges. Lets see if it can tug that silver bullit.



Bob

 

[J&LRam]

klenger

when Trailer Life mag did a article on the dmax/A and PSD/Torque shift they commented on the the trans braking, and noted that folks pullin' over 10000 lb would need a EB as the truck/trailer combo they tested warmed the brakes up real quick going down.

I lurk around on the Ford/GM diesel webs and notice that some that pull heavy have gone to EBs and some without EB have only went down a couple of mountains. I would bet they will be doing brake jobs in 20-25000 miles.

JIM