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Author Topic: Who here has had the experience of changing the powertrain in a 4104?  (Read 1260 times)
zubzub
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'53 4104. Roadworthy but rough around the edges.


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« on: March 13, 2009, 03:11:38 PM »

I don't need to do this but sometimes I worry about the whole old engine and rear dif....So if and when that day comes I would like to have a little info on hand as to what fits in there without too much trouble. 
Just the other day I saw a 671T (left hand) for sale so maybe that won't be necessary but I also know that the rear pumkin is sort of unique to the 4104 as the later transverse engined GMs used a different angle.
So one of my questions is,
1: When people put a 8v71 in there do they also transplant a rear axle from a later bus?
2: has any one put a 4 stroke in the back?
3: Do the later Spicers have a different v drive angle than the 4104's?
Any and all info appreciated, Patrick.
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Old4103
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« Reply #1 on: March 13, 2009, 04:08:55 PM »


So one of my questions is,

1: When people put a 8v71 in there do they also transplant a rear axle from a later bus?
Only if you want the driveshaft, transmission and Pinion to last

2: has any one put a 4 stroke in the back?
Lot's of different engines and transmissions have been put in different buses... After all, Some of the RTS's were repowered with Series 50's and VR731's and Cummins with ZF transmissions. Check out:  http://www.atlanticdevelopmentcorp.com/

3: Do the later Spicers have a different v drive angle than the 4104's?
Yes, the V-drive on the transmission is on the back of a 4104, and on the front of the newer coaches, (PD4106 to H8H4905A)

Any and all info appreciated, Patrick.
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Kirby-4104-FL
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« Reply #2 on: March 14, 2009, 08:23:52 AM »

Patrick, I repowered my 4104.  I used a differential from a 4106 which works well.  I'll send you some info via e-mail that may help.

Kirby
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TomC
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« Reply #3 on: March 14, 2009, 08:42:45 AM »

Some of the repowers I've seen on a 4104:
-Simplist- rebuilding the 6-71N into a 6-71T with air to air aftercooler.  With 80 injectors, you would have 300hp & 900lb/ft torque-essentially the same as a 8V-71.  The 4104 4 speed manual will take up to 1200lb/ft torque.
-8V-71 and V730 Allison from a 4106.
-ISM Cummins with VR730 (reverser gear)-also a Series 50 Detroit (Series 50 Detroits look real good on paper, but have problems of their own where I would not suggest this engine anymore, from what I have recently learned)
-6V-92 and HT740 mounted conventionally in line-but with a bump in the back of the bus because of the extra length.
You could also use the Cummins ISL at 425hp and 1200lb/ft torque with the Allison 3000 series. Basically using an Eagle rear axle that has the gear pumpkin offset so the axle faces forward with a reverser drop gear box to facilitate the longer engine/transmission, and then mount the engine fore and aft.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
luvrbus
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« Reply #4 on: March 14, 2009, 08:55:20 AM »

The easy way is a DDEC 671 in-line 330 hp I have 2 friends that have done this on their 4104's makes for nice setup plenty of power with great fuel mileage   Good luck
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uncle ned
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« Reply #5 on: March 14, 2009, 05:23:30 PM »



I used a 6v92 and v730.  also used a 4106 axel.  love the power and the auto.

 but watch for heat. Try not to go to 350 hp  it makes heat  but is nice on the road.

not to many s&s can keep up with a old bus.

Have another 4104 with a good running 6-71 but it lacks a low gear for camp ground use in the mountains.

uncle ned
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4104's forever
6v92 v730
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