4104 engine/tranny combo

[RnMAdventures]

I am in the process of looking for another bus. I have a local one in mind, but I am also looking around at other options. I considered a Prevost or Eagle, but I like the old GM coach's better, specifically the 4104/06.

In another post I saw a 4104 with an interesting engine/tranny combination. It has a Cummins Diesel LTA 10-Bus (270)with a Voith automatic transmission with three stage tranny brake. I know nothing about that engine/transmission combo. The frame was modified to accomodate the engine/tranny. Does anyone have any experience with this setup? Pros/Con's? It is supposed to get 10 mpg.

Any info would be greatly appeciated.

[gus]

Mike,

That is not an easy modification since the 4104 does not have a frame. There has to be a lot of body cutting or the engine has to stick out at the rear quite a bit to make all that stuff fit.

You need to look at this mod very carefully. If you can get someone very familiar with 4104s so much the better.  I have a 4104 for sale since I just bought a 4107 with AT & PS but if I were buying new right now I would look for a 4106 with an AT and Sheppard PS conversion because the 8V71 DD is much better with an AT. The 671 DD is great if you like to shift but I don't think it can be reasonably converted to an AT.

Also, I agree with you about the older buses. My favorite is actually the 3751 Silverside, that is one cool machine, especially the shift on the steering column and the art deco rear doors.  Prevosts are big and expensive, so are Eagles, but it is pretty much a personal preference thing. The old GMs are my favorites and the more original looking the better.

[luvrbus]

I don't think much modifications would be needed except for the transmission the L10 and 6L71 are about the same in size,I have helped a few friends install the DDEC 6L71 set at 330 hp makes a hot rod out of the 4104 and they average 10 to 12 mpg,now the Voith when in good shape are a good transmission but expect to pay around 10 grand for rebuild if it goes,lots of v drive transit buses used that setup without problems


good luck

[RnMAdventures]

Gus,

When I referred to the "modified frame" I was using the owner's words. I assumed he was referring to the engine cradle, but he could have meant the fuselage. I owned a 4104 a few years back and was never an expert on it, but I was learning. I didn't think he was referring to the unibody, but I know nothing about the combo, so he very well could have. 

I love the old 3751 SS's... the old Flxible VisaCoach is cool as well.

Thanks for the reply 

[RnMAdventures]

Luvrbus,

Thanks  for the info. An automatic transmission is convenient, but the spicer is a workhorse. Is the Alison V730 a better choice for an automatic? My wife wants a bus she can drive as well... she could handle the standard, but I think she would enjoy the automatic much more.

Thanks for the reply.

[TomC]

If you want a hot rod 4104, then quite simply find a transit with a 6V-92TA and V730 in it (there were thousands made), and swap out the whole drive train.  The 6V-92TA is a very compact engine, weighs less then the 6-71 and produces way more power (238hp and 600lb/ft torque, compared to 335hp and 1000lb/ft torque).  Lots of work, but it will be a sweet ride.  Good Luck, TomC

[JohnEd]

There is a Knut on here that put a Cum L10 in a 4106 and he converted the coach to a "T" drive.  I remember his words when questioned about not posting:  He said something to the effect" I just got really tired of people telling me this engine conversion would not work and would kill lots of innocent folk.  I understand about "MONOCOCH" and what all that means.  Fact remains that my bus has been going strong for 100K(?) and hasn't broken a single thing.  The bus is 3 feet longer but if you aren't a 4106 savvy guy you won't know that.  Bus gets 14MPG."  That was a sad post to read.  Why wasn't everybody and his wife lined up to learn HOW YOU DO THAT?  Clearly the MPG was worth reaching for and that was at 70 or some such.  He is still here somewhere.  Clifford must certainly know...he knows what was on the menu at the last supper.  That is a comment on knowledge...not age.

Pulling that off with a 4905 seems interesting but at what cost?

John

[HB of CJ]

I know that physically it is a much bigger engine, but how much sooss?  Didn't they at one time offer that mill in a pleasure boat TA version that was rated at 400hp?  Dunno.  HB of CJ (old coot)

[gus]

Mike,

I just assumed the Cummins had to go in fore and aft, but it appears from other posts that that is not the case, so my comments are not correct.

In the past I've had a few suggestions to install a 6V71 with AT from a transit but never got around to doing it. It sounds like a good fit and since the 6V71 is a lot shorter and approx the same power as a 671 it should work great.

That is really all the power a 4104 needs unless you are in a big hurry. I agree with TomC but my concern is all the extra heat from the 6V92 and more fuel consumption. A 6V92 certainly would make it move out but I'm more into casual touring than dragging!!

Instead of doing all that converting I just went ahead and bought the Hicks' 4107 but the 4104 was a lot of fun and I kind of miss it. Even with the 8V71 I find the 4107 is no quicker than the 4104 because of the extra weight but it sure is nice not worrying about having to stop on an incline with the 4-SP. The too-high first and reverse gears on the Spicer are a real pain, otherwise it is cool shifting it.

[TedsBUSted]

It's just that a T-drive opens up so many good repower options.


I sort of remember seeing a very detailed T-drive conversion thread several years ago, but I don't recall the details or site. I don't believe it was here.

I measured a 4104 to size it up for T-drive conversion, but it looked too complicated to be worth pursuing and I forgot about it.

Ted

[gus]

Ted,

I think it has been done by either hanging the engine pretty far past the original setup by using a greatly modified rear cover.

I'm a great Cummins fan for trucks but prefer the DD in a bus because it is so much smoother. The great low rpm torque of a Cummins is nice, but otherwise it is really rough compared to a DD. Nothing else sounds as good as a wound DD either!!

[TedsBUSted]

The big problem was driveshaft angle. I considered reversing the axle housing to front-mount and then going past the differential and sending powering back via drop box, or possibly a remote-mount transmission. But then you're back the the inefficiency and losses of  V-drive's extra gears. Maybe Crown style "belly-drive" would be the way to go? But... now with so many cheap powerful bus options available, it'd hardly be worth the fight.

Of course even the NA 6-71 would be much more tolerable with a few more cogs.

I have a solid CA '04 shell, but I keep thinking that I won't be happy with the 6-71's "steam" and will end up burying myself in a complex repower that I don't need in my life right now, or then, so I'm dragging my feet on the conversion and continue to bus shop.

Ted

[RnMAdventures]

TomC,
I am not looking for a hotrod, but this bus is out there and the engine/tranny is unique to the bus. When it comes to the turtle and the hare, I definitely prefer the turtle... slow, steady, and reliable. (heavy on the reliable)

JohnEd,
I remember the guy you are talking about with the 4106. Did he ever post pic's? I wonder how he is doing now? It would be interesting to see how his setup is working today.

Gus,
The only issue I have with the 4104 is the mountains. I never drove it in the mountains, but I know a lot of folks have. Sent you a PM.

[Geoff]

They are getting harder to find, but there were transit buses built with 6-71TA's and V730's.  You need the rear end out of a 4106 to get the right diveline angle but if you want more power without a lot of fab work that is the ticket. 

[Hard Headed Ken]

If you use an Allison V730 you will have to use a differential from 4106 up. I think that would go for any V drive transmission made after about 1960. If I remember correctly the Allison is 65 degrees and the original 4104 and back is 57 Degrees. If you use a 6V92 / v730 from a transit bus the 15 degree bell housing is the only one that will work without modifying the bulkhead or tailgate. Deans  coach did several 4104 repowers where they completely removed the first bulkhead and hung everything on the second. I think it was a little cleaner setup allowing plenty of room for an over sized radiator (which you will need) and the muffler. My old 04 is in Tuscon and Uncle Ned is in NC, both have the 6V92 / V730 setup. It's not much more trouble to install a Series 50 / VR731 setup from a transit bus. The only disadvantage I can think of with the Series 50 setup is that it wasn't designed to run at 2100 RPM and gearing selection is limited with a V drive unless you want to go the trouble to custom build a 4 speed 730.

I just was not satisfied with the power of the 671 and the manual transmission in my 04. It had a Hydra-Shift transmission, a 4 speed with a splitter giving 8 forwards and 2 reverses. The hydra-Shift was supposed to be the hot setup. No one could shift it but me and sometimes I would grind. The 6V92 / V730 was so much better. Great power and no grinding.
I don't see that much would be gained with a 6V71 swap.


Any engine swap is a big job.

Ken