Help me decide on engines and transmissions (Thomas FS-65)

[whitieiii]

I love the FS-65.... always have but never been on one or seen one up close....they are still the best looking bus to me! I am looking and won't buy until the right one comes along but want to know what I should buy? I am only looking for 2004-2007 Thomas models with the current style dash.... I'd love a crown model but the pre-2004 FS-65 dash really bugs me so much! what I want to know is what engine ant tranny would you want in it for use as a conversion? I always hear the 5.7 L engine and entry level Allison 2000 I believe it is, while a great pair, that combo is always talked about as being underpowered for that bus and with all the conversation mods it may make it worse! i also hear the 6.4L engine either drinks or leaks oil or both and that's not what I want! my original choice was going to be the 7.2L with the MD-3060 but is that really the best choice? Let me know i'm open to all feedback!

[whitieiii]

sorry! bump

[PNW_Steve]

Howdy!

I don't know much about the FS-65 but a little research tells me that, in that year range, they cam equipped with one of the following:

7.2L Caterpillar 3126/C7 I6
5.9L Cummins ISB I6
6.4L Detroit Diesel/Mercedes-Benz MBE900 I6

Of those three the 5.9 Cummins is the only one that I would get excited about. From a power standpoint, the Cat would come out ahead. Affordability & availability of repairs would favor the Cummis strongly.

I am afraid though, that the 5.9 may be a bit modest on the HP side for a rig that size as a highway rig. My preference would be an 8.3 Cummins (imagine that....) but it was not offered in that bus.

As far as transmission goes, in those years i would expect to see an Allison 2000/3000 series. Either one would be fin behind the 5.9. My preference (today) runs to the MD-3060. I think that you would be hard pressed to hurt the MD-3060 behind a 5.9. The 2000 or 2500 is a newer design and able to handle the 5.9 acceptably. I have heard some tales of maintenance challenges and rough shifting in the 2000's.

I am sure that the subject of increasing the power in the 5.9 will come up. Keep in mind that there is a reason why when you buy a 5.9 in a 11k lb GVRW vehicle you will find options well over 300hp (with a little work mine makes about 425). And when you buy a 26k lb GVRW rig your factory horsepower options are closer to 190hp-260hp. It is all about reliability and longevity.

One more thing regarding the 5.9 Cummins, it is not a "wet sleeve" motor like the Cat and cannot be rebuilt "in-frame". I would still stick with the 5.9 myself.

Good Luck!!

[whitieiii]

Originally Posted by PNW_Steve

Howdy!

I don't know much about the FS-65 but a little research tells me that, in that year range, they cam equipped with one of the following:

7.2L Caterpillar 3126/C7 I6
5.9L Cummins ISB I6
6.4L Detroit Diesel/Mercedes-Benz MBE900 I6

Of those three the 5.9 Cummins is the only one that I would get excited about. From a power standpoint, the Cat would come out ahead. Affordability & availability of repairs would favor the Cummis strongly.

I am afraid though, that the 5.9 may be a bit modest on the HP side for a rig that size as a highway rig. My preference would be an 8.3 Cummins (imagine that....) but it was not offered in that bus.

As far as transmission goes, in those years i would expect to see an Allison 2000/3000 series. Either one would be fin behind the 5.9. My preference (today) runs to the MD-3060. I think that you would be hard pressed to hurt the MD-3060 behind a 5.9. The 2000 or 2500 is a newer design and able to handle the 5.9 acceptably. I have heard some tales of maintenance challenges and rough shifting in the 2000's.

I am sure that the subject of increasing the power in the 5.9 will come up. Keep in mind that there is a reason why when you buy a 5.9 in a 11k lb GVRW vehicle you will find options well over 300hp (with a little work mine makes about 425). And when you buy a 26k lb GVRW rig your factory horsepower options are closer to 190hp-260hp. It is all about reliability and longevity.

One more thing regarding the 5.9 Cummins, it is not a "wet sleeve" motor like the Cat and cannot be rebuilt "in-frame". I would still stick with the 5.9 myself.

Good Luck!!

I wouldn't rebuild without taking engine out of the bus completely.. my choice originally as I may have said was the 7.2 with Allison MD-3060 but don't know if that was the best choice.... how much output will the 5.9 make maxed out with like over bore and engine additives such as bigger turbos? not gonna buy one with a 2000 only with the MD-3060 that's a must...