4104 gearing

[chessie4905]

If you do it without using the spacer, it won't stick out. Someone posted a picture on here several months ago showing it fit fine. I then went out to the shop and measured mine, (4905) which doesn't  use a spacer, and added that to the rear of the bell housing of our 4104. It fits fine. If I knew this 10 years ago, I would have changed the 4104 over. Since it had a turbo, power wouldn't  have been an issue. Yes, you will need a donor rear from a 4106,07,08,4903,5. But you will also score larger rear brakes in the process, and a rear sway bar if rear comes from a 4905.

[Jay52999]

Thanks so much for all the info. I will be fabbing a proper hitch before I tow.
Don't mind losing top speed ill be looking for 4:56 gears! Sounds like the most inexpensive route.
Bus does 70 + no problem its was parked for almost 20 yrs took 3 weeks to get her fired up replaced all rubber hoses, fuel lines brake lines, only issue is gov on air comp builds past 130 dont think its plumbed right any knowledge would be great!!

[richard5933]

Likely the governor needs to be replaced. Make sure the signal air line that the governor uses to read the pressure is sending air back to the gov (not blocked or disconnected).

[chessie4905]

Easiest is to just replace Governor. Very inexpensive. Remember that the differential has to come from old look city bus with inline 6-71. The new look, commonly called fishbowl use a different angle differential. Also find an old look with the automatic, as better chance of correct ratio. City busses of that era may have come with a couple of different ratios. Maybe someone on here has an old parts manual forcone.Make sure ring and pinion looks good and have bearings checked for condition and new pinion seal. Find one that does differential work.

[RJ]

Thanks so much for all the info. I will be fabbing a proper hitch before I tow.

Jay -

Since you've said that you're towing a heavy trailer, perhaps you should seriously consider investing (yes, that's the correct term I want to use here) in a Trailer-Toad to completely take the tongue weight off the engine cradle. By doing so, the stress is more manageable when your bus hitch is tied into the lower radius rods. The cost of a TT is going to be far less than the repair costs if you end up with your engine on the ground because the cradle failed.

FWIW & HTH. . . 

http://trailertoad.com/

[luvrbus]

Tom -

A V-730 bolted to the 6-71 will hang out the passenger side of a 4104, plus the driveline angle will be all cattywampus, thus chewing up U-joints.

Those that have installed a V-730 have also repowered to either a 6V92 or an 8V71, and replaced the rear axle for one out of a 4106 or later V-8-powered GM coach.

Problem solved.

There are few 4104's out there with the series 50 and V731 from the RTS me I prefer the DDEC 6L-71 with the 4 speed @ 330 hp they seem best suited and look better too 

[TomC]

6-71 sounds a lot better than the Series 50

[uncle ned]

From a old MG owner  than 4 stroke 4 cylinder engine sounds awful good.

If that was available when i did Huggy that is what she would have.

#350 hp and no heat.

To late now.

uncle ned

[chessie4905]

I've heard them idling at Disney world. Sounds like rocks tumbling. They have a low frequency sound and coarseness when accelerating. I think 4104's are getting too old to repower anymore. Better to move to newer coach.

[Jay52999]

Tank you everybody for all of the awesome information this forum is great Yes I am very careful with where I take it I am very interested in what I can do for more power I don't have deep pockets by any means It sounds like I'm geared really high  I'm thanking 4 : 11 or 456 would be a great idea  Other question I have is what is my cruising rpm Is 2400 too much??

[dtcerrato]

2400 rpm is a little high for the bus IL671. 2250 is what da book calls for. Is 2400 rpm too much, probably not. There"s a few bus nuts that have their 671 wound tighter than that.

[dtcerrato]

I think 4104's are getting too old to repower anymore. Better to move to newer coach.

That's a sentiment not shared by all. There's lots of bus nuts going after & bringing back to life pre WW2 antique busses. Running our 04 for 40 years and love every bit of it. That's my story & I'm stikin' toit. 

[uncle ned]

Someone with a 4905 thinks a 04 is old.

Uncle ned

[chessie4905]

I've had a Brill, I've had a 4104, and now a 4905 which is getting old also. Our 4104 is, was  62 years.. geezer status, classic or not.😂

[TomC]

As far as rpm speed for the 6-71, Detroit's last turbocharged, intercooled marine engine was rated at 485hp @ 2,500rpm from Detroit's factory. But of course you have the entire ocean to cool it. Good Luck, TomC