Seems like it's my turn to have one problem after another...been one of those weeks.
Allison V730 has been working well and shifting as expected, at least until Wednesday. Slowed down on the freeway to negotiate a somewhat hairy interchange, and when I tried to accelerate again to freeway speeds something was wrong. Seemed like I was hitting the governor at about 45 mph and no more shifting in sight. Prior to this I was easily able to get to 70mph or a bit more.
I feel one smooth shift about 20 mph, another in the mid-to-upper 30s (a bit harsher than the first), and then that's it. My tach is still not working well so I really don't know the exact engine speed when all this happens. When I get to the mid 40s the tach shows 2500 (but I think it's reading a bit higher than actual). I'm guessing that either my torque converter is not locking OR I'm missing a shift somewhere.
Any thoughts on what's going on? If nothing else, perhaps someone could tell me what the 'proper' shifting pattern of the V730 should be.
Thanks.
Richard
The governor will prevent a up shift, have you checked the fluid level the V730 will not up shift if the fluid is low start there
Best I can tell the fluid is at the correct level. Engine idling on level ground fluid at at the mark. Although I was somewhat confused - there are three marks. There is a mark with the word 'cold' next to it, one with the word 'hot' next to it, and then a few inches further up another mark. The first two I figured were for the engine cold/hot. Can't figure out what the third mark further up the dipstick are.
Governor? Are we talking about the engine governor here? Or, is there another one in the transmission somewhere? If it's the engine governor, how is it connected to transmission shifting?
Thanks!
Plugged fuel filters ( or any power loss) can also cause shifting problems.>>>Dan
The transmission has a governor all older Allison's use the same governor,there is a cover with 4 bolts and the governor is inside there the plastic gets old a brittle then breaks they cost around $150.00 for a replacement ,a bad modulator or adjustment can cause shifting problems also.If you have a air throttle check the 1/4 inch line going to the modulator for breaks
I always tell people to add a gallon of ATF and take the bus for a ride and see if the third gear shift returns. If not, then do what Cliff suggests.
--Geoff
On a manual V730, 1st, 2nd, and 2nd lockup are controlled by the throttle modulator-and that sounds like it is still working well. You get 1st converter, shift to 2nd converter, then the bump is the torque converter locking up in 2nd. 3rd is strickly a speed shift-no matter what the throttle position is. This is contolled by the governor-so I agree with trying extra trans fluid, then if nothing, the governor is bad. Good Luck, TomC
Thanks guys for the advice. Glad to hear that the problem might not require a transmission rebuild.
I'll run through the list and see what happens.
Not much to go bad on governor,look for stripped teeth. If they look ok, hold governor with teeth up in air. Move weights together while watching if spool valve moves up and returns down when you release weights. The movement of the spool valve can be seen through the slots. If it does not move, clean it in solvent till it moves up and down without sticking.Basically it is a larger version of a GM car governor. When this symtom happened in the cars, it wouldn't shift out of second into third and you would find that nylon gear stripped.
I had the same problem and it was a tiny air leak in the air line that went to the trans.
You might want to check the governor filter(screen) while you're at it. It's behind a plug in the valve body almost directly below the flange that the driveshaft attaches to. It's an often overlooked item.
Bob
i would never add a gallon at a time...even if i knew it said it needed it...1 quart and check...at operating temp. i am never in a hurry :)
On big rig engines and transmissions, when indicated that it is at the low mark, that means to add a gallon, not a quart. Good Luck, TomC
Quart or gallon, my dipstick is actually showing the level to be spot on. Any way that a dipstick can be out of calibration? If so, how does one know how much to add?
Also, I don't seem to be able to get the dipstick out of the tube with a totally clean reading - always seems to be a bit of fluid up and down the length.
Richard
We always read the lower fluid reading, looking at both sides. Wipe it off and then insert and check. You can do this 2 or three times and reading should be consistent. Me, I'd remove and check gov first, so I wouldn't have to remove a gallon of fluid after the problem was governor. Does your trans. drip or leak any oil causing it to be too low?
Are you checking at Cold Idle or Hot Idle? My HT740 Mechanic's Tips manual says to normally check only at Hot Idle (I can't remember what temperature is defined as being hot enough), and that checking at Cold Idle should only be done when the transmission is being initially filled after service, or something like that.
John
Quote from: TomC on July 16, 2017, 06:02:39 PM
On big rig engines and transmissions, when indicated that it is at the low mark, that means to add a gallon, not a quart. Good Luck, TomC
depends on a lot of things..temp is one. but adding a little at a time is a lot easier than taking a cup full or 3 quarts out...over full is just as bad as not enough.
Good Luck, DonaldP
Eagle makes a good point.Unless you have a noticeable significant leak, and the problem is low fluid level, or it it from small leaks/ drips over time, adding a quart and then road testing it would be better than using a whole gallon and then end up removing it.Btw, removing governor is easy. Remove four bolts, remove cover, remove governor by rotating slightly as you pull it out. Put a catch pan underneath to catch any spillage of fluid.
I don't think anyone has mentioned that there is a 3rd gear low fluid shift inhibitor switch when the V730 is one gallon low. That is why you dump a gallon in to see if 3rd gear comes back.
--Geoff
For those with an air throttle, do you use an air regulator between the throttle slave servo? Or do you just use the same air pressure as at the servo? If you use a regulator, what is your pressure at the modulator. I had a Wanderlodge and put air throttle on it and had to regulate it down or it would not shift until the engine was almost on the governor. I have the V-730 in my 4106 and put an air throttle on it. The PO had the tranny rebuilt shortly before i bought it last March and the shop that did the rebuild could not get the old cable between the engine and tranny adjusted properly so they removed the cable assy. I live in the flatlands so if I need to downshift, just move the selector. I have the air modulator, just have not installed it.
It has been emphasized here to make sure that the line to the modulator and to the throttle be same length and diameter.
No one here ever does it but you are supposed to have Bendix DC-4 valve at the slave to prevent a back flow 20 to 25 bucks and it makes a difference in the down shifts
Do you need the check valve on a 740 ? Mine sometimes down shifts rough . Back to the 730 mine when low also misses 3rd add a quart and she shifts great! I can usually tell when it's starting to get a little low .
I always use the DC-4 on the 740 ,all military trucks with air throttles and Allison's use the DC-4 valve
Update on where this all sits for now...
The bus is back at Interstate this week. They had a few loose ends to tie up from their work earlier in the month. I had them look at the transmission while it is there. They found two things.
1 - The tach is pretty far off and is reading a much higher than actual engine speed. Transmission does shift all the way through the gears if pushed to proper speed. I was afraid to push due to the false reading on the tach.
2 - The tech tweaked the settings on the transmission governor. It sounds like they were close but he felt that they could use a bit of adjusting.
Apparently they now report that the transmission is shifting properly. Guess I'll have to find a new tach to work on the bus. Luckily the pulse generator and wire from engine bay to tach are all intact. Just need to order the tach.
Now if only he could get the Jake brakes to work properly (if it's not one thing it's another...)