94 Ranger XLT 4x4
4 l. auto (A4LD)
67,000 km
40,000 mi

1st issue (last week):
The tranny was shifting hard up and down ( a firm clunk) @ about 20 mph. My
mechanic had the dealer check the tranny codes and they said it was the
modulator valve.  I had my mechanic change the valve last week as well as the
fluid as per Trans Surgeons recommendations.  That being drop the pan and filter
rather than flush so not to disturb anything in the converter. A cooler line had
recently started leaking so I had those replaced as well.

My mechanic said that he also added some tranny fluid conditioner. Since then
I've noticed a slippage on acceleration at the same 20 mph area where it used to
clunk. Plus now on occasion there has been a grinding noise in reverse. It also
seems to start out with a harder grab from stop now. If I gently accelerate,
keeping the RPMs under 1250 I don't notice any slips and the shifts are quiet.
Since most of my driving has been in town since the changes, I took it out for a
highway run today hoping that might do something  or show other symptoms before
going back to the mechanic Monday. It didn't seem to help and I have barely used
a 1/2 tank of gas since the work was done.

Any suggestions on what this might be? What to check for or what to do?

2nd issue (today):
After reaching our 1st. destination of the short 40 minute highway drive, we
stopped for about 15 minutes. I pulled back onto the highway and as I was
accelerating up to 50 MPH there was a rattling and lots of white smoke started
coming out of the exhaust. I let up on the gas and the smoke petered out soon
stopping. Our next stop (and a phone) was just down the road so I continued on
watching for more smoke, which never happened and kept a close eye on the gauges
which all stayed in the normal range.

When we got to our next stop, I checked under the hood with the engine running.
The coolant looked normal with no visible leaks. Tranny fluid looked normal.
Then looked at the oil dipstick thinking I might see signs of water, it was
clear. then I pulled off the oil filler cap, and gobs of white smoke started
coming out the exhaust again. There was no sludge under the oil cap. I shut off
the engine and called for a tow truck.

BTW I had the Oil and filter changed last week as well as passing the E-test
with flying colours.

I'm thinking this is a head gasket, but wondering if someone might have other
thoughts or suggestions on things to check for.

Thanks.