Transmission slippage problem.
I have a 1992 Georgie Boy motor home on a Ford F Super Duty chassis which just passed 100,000 miles. Loaded weight is approximately 18000 lbs, engine is Ford 460 fuel injected, transmission is E40D, and we typically tow a 01 Hundai Accent (1900 lbs).
At about 60 mph, 2200rpm, the tranny slips and the tach will jump to 2400 rpm, then back to 2200. This occurs both in and out of overdrive, and doesn’t seem to occur until the transmission is quite hot and outside temperatures are warm.
The problem surfaced on a final summer trip last Sept, and after 200 mi in hot weather, the tranny dumped some fluid. My local transmission shop was neither able to duplicate the problem, nor find any trouble codes stored in the computer, however it was already colder when they checked.
On a recent February trip to Arizona (cold temperatures), the problem seemed to be gone, however reoccurred on a side trip to Mexico (much warmer weather). The problem ceases if I apply enough throttle (down to 2-3 inches of manifold vacuum) and hold it there going uphill, but reoccurs when I back off the throttle.
I spoke to two transmission shops in Phoenix, both of which suggested the torque converter was loosing its lock, but both suggested it was not a transmission problem, but something that was sending a “hot” signal to the trans and thereby causing it to unlock.
The trans has a slight leak somewhere, but the fluid has been kept up, although it has not been changed in the last 60,000 miles It is still pink, and I have been advised that changing the filter, or flushing the system would likely not solve the problem.
Any suggestions?

 

stand-by Mark will respond with thoughts soon. He is a Trans Eng (used to be) with Ford.

 

Did you have Mercon V put in it when you did have the fluid changed? Mercon V is the required fluid. It will help with the slip you describe unless it is already too late.

 

The fluid was never changed, only added to. I used whatever the Ford manual called for. Bill

 

I would change the fluid and if it's only happening when it gets hot I would invest in a good trans cooler and gauge. Even if it turn's out to have some work done on the transmission these two items should be standard equipment on a rig like that.

 

No it won't. MERCON V was developed to help shudder problems, not slipping.

You most likely have a cracked piston in the torque converter clutch. It was common on E4OD torque converters before they were improved in '95. I had one of those, too. The only fix is to replace the torque converter.

 

So could he continue to run it, just carefully for a few more months or do you think it is on it's last legs?

 

The coach already has a transmission cooler. Would a cracked TC clutch piston be consistant with the hot temperature issue and with low vacuum locking up properly? And what about my high temperature fluid spill?
Thanks,
Bill

 

The cracked piston can cause all of these problems.

At low vacuum you have high engine torque. The cracked piston is leaking pressure that should be holding the torque converter clutch applied, so it slips. It gets worse hot because the fluid is thinner hot and leaks through the crack easier. The slipping torque converter creates A LOT of heat, and that can create a leak.

I think you need a new torque converter.