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 1993 Thomas, 5.9 Cummins, AT545
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professorwrench
Active Member

United States
16 Posts

Posted - 07/11/2008 :  2:40:16 PM  Show Profile  Reply with Quote
I was wondering if anyone has had experience with an older Thomas Safe T Liner with a Cummins 5.9 and an Allison AT545 transmission just being gutless. I started working for a private school just under two years ago as their mechanic and when I arrived this Thomas was not running. The bus was purchased from a public school district by the decision of my predecessor and everyone has basically accepted the bus as being slow and gutless. I was wondering if I should accept that also as I don't know how the bus would perform when new. The latest work I have done is changed the transmission fluid to a para-synthetic fluid which dropped the temp 100 degrees and improved lock up and I changed the trans modulator which greatly improved kick down when climbing a hill. With the Engine and transmission configuration my thought has been the bus is under powered for the size of carcass that it has to push. Is that right?

ModMech
Top Member

USA
948 Posts

Posted - 07/11/2008 :  7:23:11 PM  Show Profile  Visit ModMech's Homepage  Reply with Quote
The 6BT5.9LT was no slouch. They were available to 230HP+, but given this unit has the AT545 I doubt it makes more than 210 HP and 650 lb-ft of Tq. That's not very much for that weight of bus, but our '94/5 AmTran REs had a similar rating with the T444E and did just fine.

Are you getting FULL throttle?

Is the aneroid signal tube sealing properly, I have found MANY that are loose and leaking preventing the engine from reaching full power.

If you want customer service, you NEED an International!
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busgeek++
Advanced Member

United States
253 Posts

Posted - 07/12/2008 :  05:33:22 AM  Show Profile  Reply with Quote
The AT545 has no lockup on the torque converter, which is part of why then run warm. Also, ModMech, the AmTran RE wasn't available until '96.

Buses are not a way of life, they are life
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ModMech
Top Member

USA
948 Posts

Posted - 07/12/2008 :  10:04:06 AM  Show Profile  Visit ModMech's Homepage  Reply with Quote
Well we got ours in January of 1995 as I recall, but that was well over 10 years ago, so my memory might not be 100% on that. I do know two things for sure, we got two of the first 20 built for delivery, and we got them in January.

Now that I think back, they were part of the "140" series of numbers, we bought two more blocks with the 150 and 160s, the 160 levels were delivered and in-serviced before I left that firm in June of 1997, so the REs HAD to have been delivered in Jan of 1995, the 150s were Aug 1995 and the 160s were Aug 1996. I had ordered the 170s in May of 1997, but delivery was not scheduled until August.

One other thing that I should add, I worked for the AmTran distributor, so it is possible that the owner got very early models. I don't have the VIN numbers, so I don't know for sure.

If you want customer service, you NEED an International!
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L.J.D
Senior Member

United States
173 Posts

Posted - 07/14/2008 :  04:27:35 AM  Show Profile  Reply with Quote
My former employer had a fleet of 50 Thomas Cummins powered. The most common problem with the 5.9's i had was the throttle lever on the side of the injection pump. The springs would wear out and you couldn't get full throtle, a valve adjustment would help too. I also found a few of them that had bad turbos. well good luck
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professorwrench
Active Member

United States
16 Posts

Posted - 07/16/2008 :  1:26:58 PM  Show Profile  Reply with Quote
When I first started at the school here the bus was not running and I found that the fuel shut off had broken cap screws. The left over studs were in the top of the fuel pump where the aneroid limiter is on the top of the pump. This led to some time spent around the pump and I did find that the throttle linkage was installed wrong. I ended up boring and retapping for the cap screws and reposition the throttle linkage. This helped gain some Horse Power back then. I rechecked the throttle and aneroid tubes as suggested and everything is in position and the throttle goes to the stop. Someone else mentioned 220HP. This engine is only rated at 180HP. Does anyone know if there is a hard parts change for injectors and turbo required if I was to turn the pump up to 220HP? I would not mind if the engine melted down. Also I have good spool up of the turbo and the engine runs up against the governor without hesitation. I have been wondering about a leak in the air to air but have not found any cracks. Thanks for your comments and suggestions.

Do it right the first time or do it over when you don't have time.
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professorwrench
Active Member

United States
16 Posts

Posted - 07/16/2008 :  1:30:31 PM  Show Profile  Reply with Quote
Oh I forgot to mention that when I found that the fuel shut off was just hanging there I also found that the fuel pump only had one nut holding it on at the flange. The second nut was gone and the rear support bolts were gone. The injection lines were basically holding the pump in place. So by the time I was done something had to cause improvement in the way the bus ran.

Do it right the first time or do it over when you don't have time.
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baptistbusman
Advanced Member

USA
301 Posts

Posted - 07/16/2008 :  2:14:01 PM  Show Profile  Reply with Quote
wow, been there with the loose pump. Had 4 or 5 do that. I had one break off the entire throttle arm from the top of the pump. Basically they get out of time when they are loose.

Also, probably on the drivers side of that engine, there is an adjustment on the throttle cable. Mess around with that, and you'll see a huge improvement.

Watch the new nuts you put on those pumps, they will back off overtime.


1 Timothy 1:15 This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief.
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origcharger
Top Member

United States
619 Posts

Posted - 07/17/2008 :  11:21:39 AM  Show Profile  Reply with Quote
quote:
Originally posted by ModMech

The 6BT5.9LT was no slouch. They were available to 230HP+, but given this unit has the AT545 I doubt it makes more than 210 HP and 650 lb-ft of Tq. That's not very much for that weight of bus, but our '94/5 AmTran REs had a similar rating with the T444E and did just fine.




AFAIK with an AT545 the engine torque should not be more than 485 lb ft.

Operating; Seven T444Es, One MaxxForce 7, One VT365, Four DT466s, One E-450 6.0 and one Mercedes in a C2.
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professorwrench
Active Member

United States
16 Posts

Posted - 10/29/2009 :  11:23:21 AM  Show Profile  Reply with Quote
So I have a drivable bus finally. Since last posted the bus has had the transmission out to install a new rear main seal and pan gasket (I am not found of Cummins Crank seals), and before the transmission came out I checked the torque converter stall speed and it was weak and would not climb over a curb so I rebuilt the tranmission(found a chewed up bushing from a poor electrical ground) and installed the transmission with a rebuilt torque converter. That helped a little but still no amazing change for lack of power. The bus started running even worse and I ended up having some algae issues and a plugged filter (found that with the pressure gauges). Finally I decided to open up the Bosch fuel pump and low and behold there was evidence that someone had been there before with buggered screw heads and a missalligned fuel plate. The torque arm was not contacting the fuel plate at the bottom also so I made an ajustment to the fuel plate and closed up the pump and I have a normal driving bus. The drivers all notice the difference and the change is not so extreme that I am overfueling or causing wip-lash. I have not even had to adjust the aneroid stop for smoking. I call this bus the shop girl because of how much time she spends in the shop. Now I feel its worth working on.

Do it right the first time or do it over when you don't have time.
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schmooot
New Member

1 Posts

Posted - 08/27/2013 :  4:38:09 PM  Show Profile  Visit schmooot's Homepage  Reply with Quote
sorry to revive a super old thread but I registered to say thank you for this one.

I'm currently experiencing the same lack of low end power in 1st gear with my 1994 freightliner fl70. Can't even climb a curb. I have the 6-speed allison pushbutton in it MD3650 I believe....with the cummins 5.9.

I have replaced the very expensive transmission computer, as the old one would not allow the truck to start when cold. I am just about to attempt to adjust the recently replaced TPS, the trans computer is throwing codes 21-12, sporadically. That seems a good place to start? Or will those two not affect my issue? Should I go after the fuel pump first?

Edited by - schmooot on 08/28/2013 08:20:15 AM
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