4106 transmission swap and mpg

4106-123 · November 04, 2007, 04:53:11 AM

il looking at the v730 transmission to replace my spicer 4 speed. can you guys enlighten me as what to expect i would like to know how much of the bulkhead ect i will have to modify? any overheating problems? what will be my mpg vs the spicer? is the v730 a good choice fo auto?. i believe it heavier any future strucural problems because of the weight? thanks george

gomer · November 04, 2007, 05:02:16 AM

the v-730 is a good tranny swap andI don't think there is any modifacation needed to install. to determine speed you will need to get the rear end ratio,tire size and sometimes the tranny output ratio. I would highly recomennd a good tranny cooler or another radiator just for it. I don't beleive it has to be large tho. you will lose a little fuel milage but for the difference I believe you will be happier not having to shift gears all the time LOL
that my thoughts
Gomer

Jerry Liebler · November 04, 2007, 05:33:40 AM

To install a V730 you'll have to cut out part of a bulkhead and reinforce what's left. The swap will add about 500 pounds which it seems GM's design margin allows as many have done it with no reported problems. The swap will reduce your top speed from about 77 mph to about 71 mph (assuming 12r22.5 tires and 2100 RPM) The swap will reduce your fuel economy by about 2 mpg. Cooling problems sometimes follow this swap. Mine will stay a 4 speed stick.
Regards
Jerry 4107 1120

Utahclaimjumper · November 04, 2007, 07:05:32 AM

I installed a VS2-8 (3speed with overdrive) then installed a 5:55 rear gear set to LOWER the overall ratio to just over 1:1. My 06 will top out at 85 MPH at 2300 and still get decent mileage.>>>Dan

edroelle · November 04, 2007, 08:30:26 AM

I would hate to see this happen but, with the high prices for scrap, there is a previous bus owner in Michigan that is almost ready to scrap a couple V730/V731. His name is Bill Foley 810-869-0155 CELL.

Ed Roelle
Flint, MI

Sam 4106 · November 04, 2007, 08:51:39 AM

Hi Dan,
There is something fuzzy about your math. Would you please give us more information about your set-up? What is the final ratio of your VS2-8 transmission and what size tires are you using? At 1:1, your wheels would be turning at the same speed as your engine. I'm having a hard time figuring out how you get 85 MPH at 2300 RPM, when our 4106 would only go about 80 MPH at 2100 RPM with the stock drivetrain and the original 1100:20 tires.
Thanks for clearing this up, Sam 4106

Utahclaimjumper · November 04, 2007, 08:53:05 AM

There is also several takeouts on the E place for about $750.00 .>>>Dan

Barn Owl · November 16, 2007, 10:53:06 PM

I am a little late to chime in on this post but FWIW I have driven a stick 4106 and I own a 4106/V730 conversion. I love the auto, and it is worth the loss of mpg in my opinion. The places I go would be all but impossible with a stick (especially the backing up part). I have found that I tend to go toad free whenever possible, and that puts us in a lot of stop and go traffic at times in crowded downtown areas. That makes for anther place the auto shines. Nothing against the traditionalist, I like to stir a stick once-in-a-while, but not all that often.

Laryn

kingfa39 · November 17, 2007, 09:30:50 AM

I have done this change, i have a 06 which had the spicer, i got 10+mmpg before the change and i could run 80+ mph, i have 12:22.5 tires and a 4:10 rear end. the bulk head has to be cut out a bit and reinforced, expect to run hotter especally in a climb, the heat exchanger heats up the engine quickly, top speed on mine now 76 mph, mpg 7, thats the facts on my bus. the automatic is nice in traffic, but i would not do this conversion again, thats just a personal opinion , with fuel costs the way they are i need all i can get, also i dont like the heat , the transmission is very heavy and the flywheel is heavy. now you decide what to do. most love this transmission.
Frank Allen
4106

BC Bus · November 20, 2007, 12:33:40 PM

I have a very good V730 that I took from a strong driving bus that had a worn out engine. $400.00 in Portland Oregon. I will crate it up for shipping. Weighs 900lbs.

RJ · November 20, 2007, 09:46:53 PM

George -

As others have mentioned, you'll lose some top speed with the V-730, and the fuel mileage will suffer some, too.

However, there is a way to gain a little of that back - change wheels/tires.

But first, some background info:

GM designed the powertrain around tires that turn 495 revs/mile. The rear axle ratio is 4.125:1, 4th is 1.00:1, and the bevel gear for the stick shift is 0.808:1. This gives an overall final drive ratio of 3.333:1. However, the V-730's bevel gear ratio is 0.87:1, which yields an overall final drive ratio of 3.588:1, which is about 7% lower.

So, since there isn't a taller rear axle available, your only other option is to go to a taller tire. By changing to 24.5 rims, you can find 11R24.5 drive tires that turn 470 revs/mile, which is about 5% less than stock 495 rev/mile. Between the transmission and the new tires, you end up with a net loss of about 2%, which isn't much. I haven't found any 22.5 tires that turn 470, most are in the 490 - 505 range.

Clear as mud?

Any way you look at it, converting to a V-730 is a lot of work, but the vast majority of folk think it's well worth it.

FWIW & HTH. . .

4106-123 · November 21, 2007, 06:10:32 AM

i found a engine that just been rebuilt and the v730 just rebuilt by allison it comes with jakes and king cruise control as a package i was going to put the whole unit in at one time. my bus alreadly has the 24 inch tires on it will that help my fuel mileage and top speed?

TomC · November 21, 2007, 08:01:13 AM

The biggest help to your fuel mileage is the lead in your shoes. A light pedal on acceleration rather than flooring it all the time makes a big difference. Good Luck, TomC

RJ · November 21, 2007, 09:08:20 AM

Quote from: 4106-123 on November 21, 2007, 06:10:32 AM

i found a engine that just been rebuilt and the v730 just rebuilt by allison it comes with jakes and king cruise control as a package i was going to put the whole unit in at one time. my bus alreadly has the 24 inch tires on it will that help my fuel mileage and top speed?

George -

Ah, that's the way to find a powertrain package!! All rebuilt with a Jake & Cruise. . . cool!

Time to get out the forklift - makes the swap a whole lot easier. . .

Be sure to reinforce the bulkhead when you cut it out for the larger V-730.

As for the tires, since you already have 24.5 rims, just wait until it's replacement time, then go shopping for those tall 470 rev/mile tires. Bridgestone makes them, IIRC.

FWIW & HTH. . .

4106-123 · November 21, 2007, 09:18:20 AM

ill get my tire size and post it does anybody know how much this package weighs? ive got to get a trailer to pick it up. my jcb backhoe has forks on it i hope it will pick it up.