Re: [A/S] Chevy Transmissions for Towing -Continuing the Discussion

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Jack,
 You're absolutely right. The 2 biggest transmission killers (besides
out and out misuse such as overloading and towing in OD when not
recommended) are lack of maintenance and heat.

As you no doubt know, you can't change ALL of the oil in an automatic
transmission, not even close. In my Dodge, for instance, I can drain
about 6 quarts out of the pan. If I loosen the valve body, I can get
another 3 or 4 quarts, for a total of less than 10; it holds 15+ at
overhaul time with an empty torque converter. As few people will bother
loosening the VB, the best they can do is change less than half the oil
at a time, so it's important to change it frequently when towing. I've
seen recommendations of 12,000 miles.

To help eliminate the mess, I soldered a fitting with drain plug onto my
transmission pan. It's a bugger otherwise, as you probably know.

Transmission oil breaks down rapidly when it's overheated. One guy
published a chart claiming that if the oil will last XX hours at temps
of less than 180, it'll last XX/2 at 240 degrees and XX/10 at 300 or
somesuch. As bad as oil breakdown, excessive heat causes seals to harden
and no longer do their job. This in turn can cause clutches to slip,
which will destroy the transmission in very short order. Even if the
clutches don't slip, other problems will ensue; I've overhauled 2
transmissions, a 700R4 and my Dodge 47RH, both because of a bad seal.
The 700R4's symptom was "long delay when going into Drive", the 47RH's
problem was "no 2-3 shift when cold". Fortunately, both were caught
before the transmission was smoked.

A good transmission cooler costs about $100.00 at the local NAPA store
and takes an hour or less to install. It's very cheap insurance. A trans
temp guage will tell you if/when your transmission is heating up and
under what conditions. Although I installed my own, I'd imagine that you
could have it done for less than $150.00, less than 1/10 the cost of a
remanned tranny.

                                         <<Jim>>