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Stall speed of torque converter in Allison bus transmission?

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Chris, sorry you don't like the one liners but Jim ask what the stall speed was for his 740 and the 8v71 and I answered him according to info from Eagle when they equipped the 05 with his setup.All of us here do things different most of the guys have 10 speed Eaton Auto shifts behind their 60 series.My 8v92 is not a standard setup I get great fuel mileage about the same as the 60 series have good torque. Right now I am working on having gears cut for my dropbox to have a 3.05 rear gear range, the reason being I want taller gears and keep my boggie's for the Eagle look. I had a new in crate C-15 625 hp Cat engine with the Cx-35 8 speed auto i was going to install in my Eagle but decided not too and upgraded my 92 with the help of a dear friend who is VP of Stewart and Stevenson of South America and so far so good have a good day
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luvrbus: It sounds liek you are having the fun I wish I could afford to be doing! Maybe once I get a job again, if this recession / restructuring / depression ever ends, I'll be able to do some mods. For now, the analysis via computer and via asking questions is keeping me suitably stimulated in the short term!

Our actual "road mileage" is probably goiung to be only a maximum of 5000 miles per year, so it's hard to justify spending any big bucks even if I HAD the big bucks, but it is nice to make the best use of what you have by knowing its strengths, weaknesses, and capabilities.

I think I'm probably going to have time to play with that computer model tonight, as I will be overnighting at Camping World so that I can get the Splendide XC washer / dryer unit tomorrow. :D Although the unit is not exactly inexpensive, it IS on sale right now, and we have been selling household furniture to enable fitting into the bus, so we have the cash, and neither of us likes using public laundromats!

Any guesses on 0 to 60 mph time for a 34,400 lb (including driver, full full, and 50 gallons fresh water!) bus with a slightly hopped up 8V71 N and Allison HT740 with 1200 rpm stall converter?

I'm thinking we need to be anticipating TENS of seconds, not seconds as the measurement scale! :D
Jim Gnitecki
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1979 Eagle Model 05 reborn around 1997
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Jim, we are going to fire up a 8v92 today we just installed in a model 07 Eagle with new rear gears also, Van will have some videos with sound for you guys nothing sounds better that a 2 stroke on the first startup.


Clifford
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luvrbus
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Yes, the theory is very helpful in planning and designing, but nothing beats the rush of actual hearing it, smelling it, and feeling it RUN!

I'll look forward to that posting.
Jim Gnitecki
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JimGnitecki@gmail.com
1979 Eagle Model 05 reborn around 1997
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This one was tough it is the only Eagle I have seen with the radiator on the passengers side lot of 3 inch copper.
good luck
Clifford
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Hey, don’t get me wrong. I love the smell of Diesel in the morning. I also enjoy the distinct sound of a Detroit two-cycle. These great engines and their corresponding Allison automatics are still used in the ARMY’s M977 Heavy Expanded Mobility Tactical Truck (HEMTT) -- the primary carrier of the PATRIOT missile system. I have had the great pleasure of having driven them. It feels like they are capable of going straight up a wall carrying a 50,000 lbs radar shelter.

http://www.inetres.com/gp/military/cv/eng/M977.html

Be that as it may, I don’t like the present road performance of my coach (DDC 6V92/Allison HT 740, 3.36 rear axle gear ratio). Simply stated, irate truckers tailgating me, trying to pass and throwing the finger while I crawl up the hill is nerve wrecking for me -- so is the weird sensation of having a virtual parking brake applied all the time…

That's why I decided to go ahead with an engine/transmission swap while focusing on the best combination of power and fuel economy. And luckily enough, I was able to acquire a low mileage “pre-EGR” DDC S-60 and Allison HD 4560(P) six-speed (two overdrives). Couldn't find a surplus HEMTT :lol:

It was actually a long and trying journey, but I finally succeeded to work out most of the technical problems (and there were many) and now I have the entire assembly sitting on the garage floor on a specially designed and fabricated dolly ready to be installed.

Indeed, we all do things differently. That’s exactly what makes joining Eagles International and this board so interesting and enjoyable.

I still don’t like one-liners, though ;)

Chris
Last edited by chrisber on Thu Jun 04, 2009 9:14 pm, edited 2 times in total.
Christian Berlit
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He who has a why to live can bear almost any how. -- Friedrich Nietzsche
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I would add one more dimension to the discussion: heat.
A higher stall speed torque converter generates more heat than a lower stall speed torque converter, because there is by definition more slip.


Jim, that’s exactly why I became rather appreciative of the technology applied to Allison transmissions.

At first, I didn’t know much and the problem with tainted info from so-called “experts” soon reared its ugly head. So, I began to talk to the hands-on guys of the drag racing world thinking that anyone who can build engines in the thousand-plus horsepower range while successfully putting enormous torque onto the pavement without smoking tires ought to have a good understanding of torque converters.

We have a great shop in this area, namely “Lew's Vinton Automotive” (I hope Lew doesn’t mind my using his name in vein). They are heavily into racing and I couldn’t believe my eyes when I first saw all that advanced “Yankee Ingenuity” stuff! They are, without question, the best machine shop around and an absolute 'wiz-bang' human knowledge base. I learned a lot from Lew, simply because he doesn’t have this annoying case of overstressed self-importance that is so widespread.

Anyway, I am sure you already know that the HT 740 in your Eagle features an automatic lockup clutch that is effective in all forward ranges (or effective in 2nd through 4th range – depending on model). With “appropriate oil cooling” and the use of the Allison TranSynd® Automatic Transmission Fluid [or equivalent meeting engineering specification 295 (TES 295) for automatic transmission fluids], the HT 740 is virtually bullet proof.

This leads me to another post on this board; i.e., Bill Klein’s engine overheating problem after swapping engines from a DDC 8V71 to a Cummins L-10 in the parking lot at an RV park in a few days…

I don’t want to meddle. But, I only hope that his coach features a standard transmission, since the performance parameters (overlapping performance curves) between the two engines (horse power, torque and RPM) are significantly different.

If he has an automatic transmission in his coach and did not change the torque converter configuration, then the higher stall toque ratio that is typically used on a DDC 8V71 will build up increased heat when it is bolted to a four-cycle engine that develops maximum torque at a much lower RPM range (so I thought...) And since there is probably a liquid-to-liquid heat exchanger that dissipates transmission heat into the engine's cooling loop, it can therefore contribute to the overheating problem.

Chris
Last edited by chrisber on Thu Jun 04, 2009 5:55 pm, edited 1 time in total.
Christian Berlit
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Right now I am working on having gears cut for my dropbox to have a 3.05 rear gear range, the reason being I want taller gears and keep my boggie's for the Eagle look.


Now, that has got me thinking :idea: Thanks, luvrbus, for mentioning that there are people in your area who can cut gears for different drop-box ratios. That’s one task no one wants to tackle here.

When you followed the threads, you probably noticed that my coach currently has a 3.36 rear axle gear ratio. I have been able to buy a new ring and pinion set that will yield a 4.11 ratio. I will have to install it soon, because my new transmission features two overdrives:

First……….4.70:1
Second…..2.21:1
Third.......1.53:1
Fourth.....1.00:1
Fifth........0.76:1
Sixth.......0.67:1
Reverse….5.55:1

As y’all painfully know, dropping the “drop-box” and disassembling an Eagle’s drive axle and differential gears is not for the faint at heart. And removing and replacing the ring and pinion gears requires vast experience and unsurprisingly involves risks of personal injury.

So I thought: “Wouldn’t it be easier to change the current 1:1 gear ratio of my drop-box to an 1:0.75 “under-drive” that would yield an equivalent 4.11:1 rear-end ratio?” Swapping the drop box gears with a higher quality set may also reduce the probability of stress-related failure when a higher output engine is used.

What’s your opinion?

Thanks, Chris
Christian Berlit
El Paso, TX

He who has a why to live can bear almost any how. -- Friedrich Nietzsche
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Last edited by van on Fri Jun 05, 2009 3:42 pm, edited 1 time in total.
van
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What a Great Sound! Don't ya just love it!

Nothing like the sound of a Detroit.......Period!

Good Job Clifford! 8-)

~Paul~
Becky & Paul Lawry
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Dreamscape Eagle Travel Blog: https://dreamscapetravels.wordpress.com/

Dreamscape Build Blog: https://dreamscapesilvereagle.wordpress.com/
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