Hi, guys

I know I've been away for a long time and I hate to pop in only when I need help but I am really scratching my head on this one.

I have a 700R4, pre Aux VB from my brothers plow/salt truck. It was previously built (4 yrs ago)by a reputable shop, and lasted 100kms after install. When I got it on Xmas it was wiped from lack of lube.

I went thru it and fixed all the buggered parts, put it back in. We got almost 400kms before trouble appeared: occasionally it begins to start in 2nd, and then give a limp upshift to 3rd. Putting it in reverse yields a bad slip. When I road-tested it the problem would persist until I let the trans cool 10 mins or so, then everything is great again.

When it works, it works well. Once it starts to slip, it slips in all gear positions until cool down. I reflushed the coolers again, and pulled the pressure regulator valve, replaced the rev/int boost valve w/the largest one I had and the TV boost valve with a .500". The regulator valve seems buttery smooth in the bore (not sticky), and the larger boost valves seemed to help but not cure the problem. It also seems sometimes that putting it in Rev and giving some gas that it slips then kind of thumps in(boost valve forcing a stuck regulator???) There is no debris in the pan (yet) and I feel if I can solve the root cause that the trans will survive so long as we stop driving whenever the slipping starts.

I don't have a pressure guage on it yet; tomorrow morning I am buying a new guage first thing. My brother told me that when it is slipping that the cooler lines feel ice-cold. My instincts say I have a pressure problem, and the pump is not moving much oil when its slipping, which is why the lines feel cold.

This truck is his only way to spread salt, and he is contractually obligated to spread it; he is nearing a nervous breakdown over this, and I am frustrated also because usually 700's are fairly cooperative for me, but not this one.

Anyone have any ideas? I still suspect the regulator. I'll post pressures when I get them. What about the slide in the pump, could that be the cause if it jams in the low-volume position? Any other ideas?

I am thinking either swap to another trans (have to finish building it first) or swap the pump (same as above, plus the only pump I have loose has been welded and remachined, and never tested...), or ordering an oversize regulator from Sonnax on Mon (I have the jig/reamer) which should guarantee a worn/leaky/burred bore isn't my issue. I'd really like to use this trans if I can fix it but the bottom line is this truck needs to go back to work yesterday!

THANK YOU THANK YOU THANK YOU THANK YOU...

if the cooler lines are cold... you have a flow problem and no lube to the tranny. The trans will sure get hot with out lube flow

was the radiator / transmission cooler checked , flushed ? Compressed air blown through the lines?

You could have a problem in the pump stator support not allowing fluid out of the converter into the cooler line that flows out of the trans. You need to check all those ports in the pump , stator , case , cooler lines for clogs and debris

Hi...The problem was very intermittent, not at all reliably reproduced. Ie, it wasn't a misbuild, clogged oriface, etc. I paid a lot of attention to all the lube feeds because the first failure was lack of lube. The cooler has been flushed once on a flushing tool, and SEVERAL times with compressed air since. It is clean and clear.

I wasn't there when it acted up the first time and they wiped it out, but I believe it would have lost clutches at the same time it lost lube. No clutch engagement is the most obvious symptom to the driver, and if you don't stop revving the motor lack of lube kills everything else. (If you can believe it, they actually thought the truck was stuck, on level ground, in 4wd, in 2" of snow...so of course rev the crap out of it until smoke comes out).

In other words, I believe the pump was intermittently not flowing any oil at all, not just a covertly clogged lube circuit.

Here's an update:

I still suspected an intermittently sticking pressure regulator as both the cause of my problem and the cause of the previous failure (or the pump slide, but since I couldn't reach the slide w/o an R&R...)

I found an oversize regulator in my goodie box, plus an o-ringed int boost and TV boost valves. Reamed it out and installed it in the vehicle along with a guage in the cab. That should cure any burrs or leaks in the regulator circut, right? Result? Terrrible! 20psi. No gears (obviously). Really really NFG.

Said the heck with it, pulled the trans this morning, found the oversize pressure regulator stuck open. Re-reamed with the jig...still stuck. Re-reamed, re-reamed, re-reamed, still sticks open, only on the last land of the regulator. It's almost like the last hole doesn't quite line up with all the rest.

Built another pump up, (checking slide clearance first) put the oversize regulator and o-ringed parts in that one plus the priming spring shim for the slide, installed the whole thing back in the truck. It's working great so far.

Its midnight here, and freezing rain, I just dropped the truck off, and my brother immediately loaded it up with nearly a tonne of salt and took off to make his rounds. I guess time will tell if this cured it or not.