V730 to V731

[Cary and Don]

Hi all,

Has anyone made this trade.  Our V730 seems a little over the hill and we have a complete rebuilt V731 we could replace it with.  This in in a GM4107.  And we have an air throttle.

Option 1..  Make a complete swap.  It would be nice to get rid of that shifter on the floor. What all is required to do this? We have the shifter pad and an electronic brain.

Option 2... Turn the V731 into a V730.  Can this be done?  We have heard that they are the same except for the electronics and the housing.

We have come to the conclusion that the engine was probably a rebuilt when we bought the bus.  It seems a shame to have this older sluggish tranny on it.

Don and Cary
GMC4107
Neoplan AN340

[NJT 5573]

Don,

The 731 is an electronic key pad transmission. It will work if you install all the electronics that go with it. ECM, 30 pin connectors, push button key pad, test light and switch on dash, etc. It needs an electronic throttle position sensor in addition.

The 730 is a mechanical unit that would be my personal preference if I could choose.

The ATEC ECM is also somewhat bulky as well as expensive and time consuming to wire but since you have it all, its doable.

When you say your 730 is sluggish do you mean it slips?

If it makes the shifts and locks up, the 731 will probably not give you a noticable change. My HTB748R is basically the same tranny as the 731. It is very tempermental. If I put it in D and leave it alone it does its thing and is happy. If I select the gears I want it to be in, it codes out,(stop and clear codes before proceding), shifts hard, refuses to shift, refuses to lock up and comes out of gear on compression, and free rolls out of gear. I think it grabs gears to soon and should whind out and hold each gear longer, but it has a mind of its own and has let me know that it is going to do things its way, so I just push D and let it do its thing and it doesn't make me look stupid anymore.

[buswarrior]

Have some older GM Classic Transits and older New Flyer D40 somethings here at big transit.

6V71 coupled to V731. Throttle position sensor mounted above the engine door, has a cable attached to the throttle linkage. Air throttle to the front.

As noted, they like to upshift early, but since the 2-3 shift is the only one that you'd be paying attention to in a 731, they seem willing to accept manual commands via the keypad. None of these transmissions readily accept manual shifting 1-2, best to leave them to do that on their own!

There are many variables in parts, settings and condition in used transmissions, then there are the variables in all of our experiences, which make the behavior or expected behavior of any one example in an application impossible to predict. I might shrug my shoulders and drive it, another might freak and take it to the tranny shop for a rebuild. Or vise versa?

I'd be curious to delve deeper into the current 730's condition and what might be wrong with it. Sometimes it's normal, sometimes an easy fix, sometimes it's doomed.

I'm into energy conservation...why tear into it if you don't have to?

happy coaching!
buswarrior

[pvcces]

Don, as far as I know, the transmission should only become sluggish with cold oil. Have you had this symptom when the transmission is all the way up to temperature?

If sluggishness develops as the transmission heats up, that could be due to worn parts.

Torque converters are at their most efficient when oil viscosity is very low. The coupling effect comes from the intertia of the oil passing from pump to turbine, not from any stiffness. If the oil is not very fluid, then the stiffness causes your engine power to turn into heat in the transmission.

Any heat generated in the transmission is power that is deducted from the output.

For what it's worth.

Tom Caffrey

[gm4106]

You can get rid of the floor shifter and still use the V730. You can use a Stone Bennett air shifter. That part attaches to the transmission. I got mine from Nimco. Made my own shifter for inside the bus. I used a rocker switch (like for electric car windows) and 5 little lights ( placing R- N- D- 2- 1 next to the lights)to tell what gear I'm in. Very easy If you go the route and need help I can offer help if needed.

[Cary and Don]

We are comparing it's operation to the HT700 series that our Neoplan has.  We you push "d" in it, you can feel an instant drop into gear.  The V730 kind of lags a second and feels like it slides into gear.  Doesn't have that crisp gear change.  It does shift up and down manually just fine.  It hasn't ever not wanted to move the bus, even up hill from a stop.  We did put an air to oil cooler with a fan, in addition to the existing oil cooler,  on it to help with the cooling.  That dropped the engine temp by almost ten degrees in hot weather.  She will cruise at 65 to 70 all day long and drops  to 45 - 50 on 6% grades. Sounds like maybe, it is normal after all.

Don and Cary
GMC4107
Neoplan AN340

[Sammy]

It will be an expensive conversion, unless you have a donor bus.
Transmission will bolt up,that's the easy part.
You'll need an ATEC ECU,shift pad,wiring harnesses for trans and ECU and a Throttle Position Sensor,schematic diagrams and possibly a ProLink scan tool (if there's big issues).
I would have the 730 checked out - hydraulic pressure tests. The valve body has test ports - 1/8 pipe thread plugs in it that can be removed.High pressure hoses and guages can be connected to valve body test ports and then bus is driven.I recommend that you look for an Allison V730 Service Manual. All this info is in it. Might help you with your decisions.

[TomC]

I had my V730 rebuilt for $6,500 (part of the turbo project that Don Fairchild did).  At the same time, they upped the pressure to accomodate the higher horsepower.  It shifts very well under full throttle.  The V730 is a dirt reliable transmission (along with the HT740 and HT754CR).  I wouldn't install a V731 just to get rid of the mechanical shifter.  You could install an electric shifter (name eludes me) that will shift the mechanical V730 electrically.  Do yourself a BIG favor and stay away from the ATEC transmission-you'll be spending alot more then you anticipate to get all the bugs out of it.  Good Luck, TomC