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Author Topic: cost of a tranny swap?  (Read 1701 times)
coolbus
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« on: September 18, 2006, 07:50:43 PM »

.....................Seems that all the early GM bus' that I've found for sale have 'four speed' trannys. I Like manual shifting, but, really, a 4 speed in a bus?  Undecided

The bus I end up with may be a 4 speed, and I may find it to be OK for me. But If I need to have it changed out (taking for granted that it is a model  that can have an auto), how much should I figure on spending to have the swap done by a mechanic? (parts & labor - maybe a good take out tranny) Huh 

Thanks alot for the responses  Smiley

mark
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NJT5047
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« Reply #1 on: September 18, 2006, 08:17:03 PM »

Find a bus that has the trans you want.  Most GMs have 4 speed manuals. It'll get you there in fine style..and faster than you may think.   But, the possiblily of smoking a clutch is great unless you're a "truck driver" that understands how they have to be driven. 
Look for an automatic.  You'll thank me later....probably. 
Are you stuck on a GM coach?  MCI, Prevosts, Eagles, and later GM coachs will hve automatics that will get decend fuel milage.   What are you looking for?  Anything other than a GM?  Whatever you want, there's plenty around. Just gotta get out and cull them out.    Swapping a manual for an auto will set you back a right good chunck of change....I'd guess it be cheaper to buy an automatic.  Most MCIs, Prevosts, and Eagles have automatic from the factory.  If you can do it yourself, you could get out cheap...maybe 4K with a donor.   
May I ask what your fascination with GMs might be? 
cheers, JR 

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
coolbus
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« Reply #2 on: September 18, 2006, 10:08:37 PM »

Hello, JR

I like the older GM's  for several reasons. They are only 35 feet, which will be an advantage to me for several reasons. I like the two axel design, smaller size. As far as floorplans go, 40 feet would be great, but then there is the issue of GROUND clearance which has me a little concerned with the 40 footers. And then theres the turning radius. 35 feet usually means more maneuverable.  Smiley

I don't know what bus I am going to end up with...so many things to consider!

Thanks for the input  Cool

Mark
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Buffalo SpaceShip
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« Reply #3 on: September 18, 2006, 10:33:14 PM »

Mark, for a v-drive GMC w/ an 8v71, you only have two automatic tranny options... an Allison VS2-8 or a V-730. A 671 has no automatic upgrade without a pumpkin/ differential change. Either tranny will set you back about a $1000 - $1500 for a decent take-out, and I'd budget another $3k for labor and parts install (bulkhead mods, shifters, etc.). For that kind of coin, you're generally ahead of the game to look for a coach that already has a slushbox... even if you have to rip out conversion items that don't suit you.

The V-730 is a more modern three-speed torque converter model. It shifts nicer and would be preferable for hillclimbing and negotiating tight spots, driving through town, etc. It is, however, a fair bit lower-geared than the Spicer and you will lose top-end and fuel economy over the 4-speed.

OTOH, the VS2-8 is very high-geared (it comes in two flavors of OD, 0.6 and 0.8, IIRC), is a two-speed with OD and will probably get better highway MPG (and top end) than the Spicer. You will have a very tall-geared coach (in a parlor coach), since these were designed for transit-geared busses that needed to get up to highway speeds. They also tend to stay in hydraulic mode (and heat up) while climbling, you can't select gear ranges in them for descending (w/o modification, anyways), and generally shifts harder in my experience with the two trannies.

This said, there are already-converted auto-tranny GMCs out there. Mine was. And like JR said, many of the newer Eagles and MCIs already have Allisons and none of the v-drive limitations.   If you're stuck on the 35' footprint, MCI 5s are 35'ers, and Eagle made some 35', two-axle models before they closed-up shop. I do understand your fondness of GMCs, though!  Wink

HTH,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
belfert
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« Reply #4 on: September 19, 2006, 05:58:15 AM »

Hello, JR

I like the older GM's  for several reasons. They are only 35 feet, which will be an advantage to me for several reasons. I like the two axel design, smaller size. As far as floorplans go, 40 feet would be great, but then there is the issue of GROUND clearance which has me a little concerned with the 40 footers. And then theres the turning radius. 35 feet usually means more maneuverable.  Smiley

Why would a 35 foot bus have greater ground clearance than a 40 foot model.  Is there some sort of major difference between a GMC 35 and 40 footer? 

My Dina is 43 feet long, yet it has tons of ground clearance.  Dina uses a torsilastic suspension and sets them up to ride high for whatever reason.  I like it that way.

Brian Elfert
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NJT5047
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« Reply #5 on: September 19, 2006, 06:55:03 AM »

The wheels being closer together on a 35' bus will allow greater clearance over high spots. 
They may not be that much closer in actuality...don't forget the tag axle moves the drive axle forward on most coaches.  This could be factored with a couple of measurments...steering to drive axles centerlines vs ground clearance would help you decide which bus would works best for you application.  The shorter coaches would clearly be an advantage in old parks.
JR 
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
Dallas
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« Reply #6 on: September 19, 2006, 07:12:25 AM »

The wheels being closer together on a 35' bus will allow greater clearance over high spots. 
They may not be that much closer in actuality...don't forget the tag axle moves the drive axle forward on most coaches.  This could be factored with a couple of measurments...steering to drive axles centerlines vs ground clearance would help you decide which bus would works best for you application.  The shorter coaches would clearly be an advantage in old parks.
JR 


JR, not just old parks, but crossing some sets of railroad tracks or certain crossroads.
I high centered an RGN beam trailer on a set of railroad tracks one time while empty. It was a good thing the tracks were abandoned as it took a wrecker 4 hours to get me loose.
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chargePlus
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« Reply #7 on: September 19, 2006, 08:54:14 AM »

Speaking of tranny swaps, I'm considering trying to add some more gears to our GM PD4103 (6-71 and Spicer 4spd) and wondering what options I have. Manual doesn't bother me or my wife. I know that the V-Drive limits our selections.

Thanks,

- John
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Sports Car Lover and Bus Nut
1951 GMC PD4103-125 http://www.euliss-uftring.org/DaBus
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Dallas
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« Reply #8 on: September 19, 2006, 09:11:46 AM »

Speaking of tranny swaps, I'm considering trying to add some more gears to our GM PD4103 (6-71 and Spicer 4spd) and wondering what options I have. Manual doesn't bother me or my wife. I know that the V-Drive limits our selections.

Thanks,

- John

John,
In GMC V-drives, gears are hard to come by.
You are pretty much stuck with the spicer 4 speed manual or an automatic.

The other option is to find a Spicer hydrashift, (of which there are very, very few), which made the standard 4 speed into  a 4X2 speed.

I have the supplement on this transmission and it looks like it was built with the planetary gears out of a VS2 combined with the spicer 4 spd transmission.

Some 4104's had them but it wasn't an option that lasted very long.

Another option I thought of was to find a ZF transmission and do some creative engineering to make it fit my 4103.

IHTH.
Dallas
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chargePlus
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« Reply #9 on: September 19, 2006, 09:32:03 AM »

Speaking of tranny swaps, I'm considering trying to add some more gears to our GM PD4103 (6-71 and Spicer 4spd) and wondering what options I have. Manual doesn't bother me or my wife. I know that the V-Drive limits our selections.

Thanks,

- John

John,
In GMC V-drives, gears are hard to come by.
You are pretty much stuck with the spicer 4 speed manual or an automatic.

Dallas,

That's what I suspected. Thanks for the info.

- John
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Sports Car Lover and Bus Nut
1951 GMC PD4103-125 http://www.euliss-uftring.org/DaBus
Sports Car Club of America http://www.ncrscca.com/
Mazda Sports Car Club of NC http://www.msccnc.org/
TomC
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« Reply #10 on: September 19, 2006, 03:24:19 PM »

Easiest swap and probably the lowest cost is to find a transit with the 6V-92TA and V730 (preferrably the mechanically injected rather than the electronic-unless you want that kind of challenge) and swap the whole drive train.  You'll go from the 6-71N of 238hp and 600lb/ft or the 8V-71N of 320hp and 800lb/ft torque to 350hp and 1050lb/ft torque.  Sounds good to me!  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
NJT5047
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« Reply #11 on: September 19, 2006, 08:37:43 PM »

For those that don't have coaches already, the easiest way to get 35' and good auto trans is buy (as someone has suggested) an MC5 or Eagle, or a T drive transit.  The T drives have Allison HT series trans (for the most part).  They are good transmissions.   The V-drive transmissions are limited by torque and HP ratings.  Not that one couldn't use a larger engine than the unit was designed for, but...you gotta think about it.   Tom pretty much cover repowering a GM.
Was a 6V92T a standard item for a GM highway coach? 
Even if you want a manual, the T drive coaches will accomodate truck transmissions.   You can have 10 speeds if you wish. 
Installing a DDEC II in a GM would be just as easy as an MUI.  As long as wirng doesn't scare you. DDEC IIs have all the components mounted on the engine.  The wring looks much worse than it is. DDEC engines are much easier to maintain...no gov, no racks, clean engine...no gummy throttle linkage.   Wink Just pull the big harness up front (the hard part) and install a TPS throttle and viola...you got an easy to drive powerplant..with cruise control built in.   The trans doesn't have to be electronic...use an ECM for a truck, manual shift, and let the trans just do what it does.   I wouldn't try to install a DDEC 1...bad idea.  Tongue  
GM coaches are limited by the HP ratings of the drive axles and transmissions, and by the gear ratios of the transmissions and drive axle assemblies.   So are all other older coaches, but you can retrofit later auto and manual trans more easily into a T drive coach. 
I cannot advise about other makes, but one can remove the engine and transmission from an MC7,8,9 without going inside the coach.  This is a serious concept in a finished coach.  Course, you can pull a GM powerplant without going into the coach too!   Food for thought. Huh
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
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