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Author Topic: Transmission Upgrade For GMC 4106  (Read 1844 times)
MysteryBus
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1965 GM 4106 8v71 4 speed Spincer




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« on: March 10, 2013, 01:25:34 PM »

I have a GMC 4106 with standard transmission. I want to put an automatic in her, I've found a VR731 for sale and I've got a 8v71 Detroit; will these two match up? Also not to sound like a complete idiot but if I freight the trans will I have to pick it up from the train station? My Step Dad said he would help put it in but, he didn't sound like he really wanted to. so if anybody knows of a place near Asheville, NC.

-MysteryBus
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luvrbus
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« Reply #1 on: March 10, 2013, 01:35:12 PM »

The VR 731 changes a right handed engine to the left handed gear train you need the V730 for the 4106,you will need a flywheel,drive shaft ,cooler , a sealed starter,some type shifter like a Bennett or shift tower and a huge hole in the bulk head that needs to be reinforced lots of work ahead of you
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RJ
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« Reply #2 on: March 10, 2013, 02:27:33 PM »

Name??? -

What's wrong with the 4-spd manual?  Or are you just tired of shifting?

Might be cheaper to buy a transit bus with a 6V92TA/V-730 powertrain in it and swap the entire assembly.

If you try to install the automatic you've found, you'll have one forward and three speeds in reverse.

It's also an ATEC unit, which means you'd also need all the electronics to get it to function properly.

Oh, and your fuel mileage will drop about 2 mpg w/ the automatic.

FWIW & HTH. . .

 Wink
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RJ Long
PD4106-2784 No More
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Utahclaimjumper
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« Reply #3 on: March 10, 2013, 03:40:48 PM »

 Is your bus equiped with the air assist or mechanical "moustrap" assist on the clutch?? These devises can be set up to make shifting  actually a pleasure.  By making certain adjustments you can reduce the workload ,,retain the good milage,, and save the money for more importand things that would return more bang for the buck..>>>Dan ( I changed to an auto to allow my wife to drive the 06 I owned,, only to find she didn't want to drive afterall)
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Utahclaimjumper 
 EX 4106 (presently SOB)
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« Reply #4 on: March 10, 2013, 04:01:05 PM »

...heavy duty, overdrive, ten speed, RTO-910 Fuller truck tranny?"  This was one of many questions I would ask prospective new girl friends when I had my Crown Supercoach ex school bus.  Had no "yes" answers...but SOME did say..."No, but I can most certainly try to learn!"

I know this may be difficult, but is there any way you can learn to shift and be happy with the manual tranny you have now?  My knees are going out...I understand sometimes an automatic is the only solution.  My read on your swap out is that it is a lot of work.  HB of CJ (old coot)
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wildbob24
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« Reply #5 on: March 10, 2013, 04:04:36 PM »

Clifford,

Correct me if I'm wrong.

I thought the VR731 designated a transmission with a retarder and the V731RH designated a transmission for the right handed engines.

Bob
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P8M4905A-1308, 8V71 w/V730
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« Reply #6 on: March 10, 2013, 04:32:23 PM »

Sorry Clifford but wildbob is right on this one you just got the R in wrong place, lol.
By the way Mystery, I have a VR731 for sale it is just 45 miles from Asheville and can also be installed where it is, or I will deliver it for free to Asheville for you.  1990 vintage transmission.  750.00.  Does not have a ECU, harness or shifter.
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Sam 4106
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« Reply #7 on: March 10, 2013, 05:25:34 PM »

Unless you are really,really in love with that GM 4106, your best bet would be to sell it to someone that wants a manual transmission and buy a bus that already has the drivetrain you want. In my opinion, there is no way that it is practical for you to switch transmissions. It just isn't feasible financially or to do all the work. But, If you love your GM 4106 enough to spend time and money that you will never see a return on, except for your enjoyment of that bus, forge ahead.

We were in the position of needing a bus with an automatic transmission because of my failing health. Just by pure luck, we found an MCI 8 with an automatic and 8V92 DDEC II and bought it. We later were lucky enough to find a buyer for our GM 4106 that wanted a manual transmission. Sure it cost us more money with the cost of the bus and catching up with the neglected maintenance but my wife could drive our MCI 8 and we could continue to enjoy busing.

Good luck with what ever you decide, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #8 on: March 10, 2013, 06:23:16 PM »

I always get that confused Mark lol I need to buy all left handed wrenches seems like all I work on is the left handed GM nowadays when I have time

 I was a happy camper when Doyle came today with a Eagle the engine setting up straight and not cross ways in the bus

Did you see the GM with the 903 Cummins and V Allison at Quartzsite it must have a rh Allison the 903 won't run backwards
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bs4104
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« Reply #9 on: March 10, 2013, 06:37:39 PM »

Clifford:
The 903 Cummins and V Allison came out of some Transits, several were swap out in Madera some 15/20 years or so ago, Don Mathews & Gary Nickerson had one for a time too. I think the were Left's to start with.  BGS
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« Reply #10 on: March 10, 2013, 06:43:23 PM »

Not nearly as bad as installing an automatic into an MCI. The hole in the bulkhead needs enlarged, but not "huge". I can supply measurements if you need. Unless a trans cooler comes with it, I'd go with an air to air unit. You will lose about 6 mph top end, and at least 2 to 3 mpg. You'll love it the first time you need to back up on a grade. I also would recommend that you seriously consider getting a 6V92 with the trans already attached, especially if your engine is tired. Just round up the necessary parts. You might desire to add the small air bag support at the outer edge of trans, although will work fine without it. I haven't looked lately, but you used to be able to swap the valve body to change to the electronic version; the case and guts were the same. Maybe able to change back to manual version. You will need to study the parts manual for the trans. They used to list a changeover kit to go to electronic version.
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« Reply #11 on: March 10, 2013, 06:45:39 PM »

No I didn't see that one Clifford, I was in and out of Quartzsite pretty fast this year.  Sorry I missed you.  Did you see the pictures of my engine and installation?  Everything is on the outboard side of the engine, virtually nothing on the back side, very easy to work on (unless you want to peek in the airbox covers, lol).  Sure don't sound like the normal 6-71.  Got the power steering in, just testing everything now.
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« Reply #12 on: March 10, 2013, 06:59:31 PM »

Bruce I never saw a 903 left turning engine but I have saw the V730 work on right handed engines Kim at Global in Tucson was a master at converting a V730 for a right hand turning engine to work on a V drive transit 
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bs4104
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« Reply #13 on: March 10, 2013, 07:13:03 PM »

Gary just said he has the factory manuals for it in Havasu, because he had two of them at one time and yes they are left turning. BGS
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luvrbus
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« Reply #14 on: March 10, 2013, 08:09:14 PM »

 I just never saw a lefty 903 Bruce I checked all the manuals no mention of one maybe Cummins made a few for the transit world  I bet the PT pump would be nightmare to locate if needed one
 
I know I don't want left or right turning 903 a 14.8L engine that is 270 hp with 700ft lbs of torque @2600 rpm is not much IMO, one round with a V555 was enough for me in a Wabco scraper we replaced it with  a 6v92
« Last Edit: March 10, 2013, 08:22:50 PM by luvrbus » Logged

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TomC
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« Reply #15 on: March 10, 2013, 09:41:11 PM »

Cummins still makes the VT903 for the Bradley tank. They have installed electronic common rail fuel injection and it now puts out 700hp and 1500lb/ft torque. Course, the military only has a 2,000hr life expectancy requirement on their engines too. Actually-2,000hours would be around 100,000 miles-so that would work for the vast majority of us. Still would not run a VT903. The new ISX12 at 500hp and 1650lb/ft torque (RV rating) is far superior.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #16 on: March 11, 2013, 04:57:34 AM »

Contact Bill Gerrie (I see him Posting alot on BNO), he can tell you all about how to take a V731 to a v730. Not that bad from what I have been told. I agree with many here, find the 6v92ta/v730 setup. Makes a great upgrade, and a hill climber like none other.
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« Reply #17 on: March 11, 2013, 07:26:10 AM »


If you are in Ashville. Just run down to Mills River and see Gene Russell. That will be the end of your troubles.

He works wonders with old gm buses.

ned sanders
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MysteryBus
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1965 GM 4106 8v71 4 speed Spincer




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« Reply #18 on: March 11, 2013, 01:44:14 PM »

Thanks everyone for your input. I wanted to change the trans. for my wife mostly, but with the no power steering she can a bit of a beast, another project i'm looking at (PWR Steering). The mousetrap clutch sounds interesting, would really like to get the 6v92 just don't know if i can afford that right now.  I guess I will mow over these ideas and figure out the best option.

-Jay MysteryBus
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Utahclaimjumper
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« Reply #19 on: March 12, 2013, 05:43:37 AM »

 A "moustrap" is not a clutch,, its a spring loaded overcenter device that assistes in releasing the clutch when the clutch pedal is depressed.. There are also air assist mechanisms to accomplish the same results.. The most popular power steering system for the 4106 is the Sheppard intracal system usually robbed from later model coaches,, it makes the 06 steer like a caddie.>>>Dan
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Utahclaimjumper 
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« Reply #20 on: March 12, 2013, 04:19:05 PM »

As Utah says, get a Sheppard. The factory original hyd assist systems do nothing while cruising on straight highways and will tire you out after a long day on the road.

No question though, that they are a great help in low speed maneuvering. I would never want a straight manual, life is too short!
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