I talked to my mechanic and he said that slipping in
reverse in Chevrolets is an early warning signal that
the transmission is going bad (higher pressures in
reverse or something...) Anyone agree or disagree?
Is it going to start slipping in forward?
Jonathan Grobe Books
Browse our inventory of thousands of used books at:
On Sat, 18 Dec 2004 14:59:10 +0000 (UTC), Jonathan Grobe
Depends on why it's slipping in reverse but yes, most likely it's not
going to last a whole lot longer. The deal with the higher pressure
is that due to design issues, the reverse band had to have VERY high
pressure applied to keep it from slipping, something like 150 psi.
Normal pressure for the bands and clutches is usually significantly
lower. As the tranny wears and the pump clearances increase the pump
can't generate as high a pressure, plus all the internal seals are
getting worn and leaking more and more which requires the pump to pump
a higher volume to maintain whatever pressure is needed. So even if
nothing is actually broken but it's all just getting worn out, the
high pressure for reverse may become impossible for the pump to
If it were my car and I wanted to avoid spending more then $15 on
repairs, here's what I would do....
1 - buy a can of "STP" or other brand of oil viscosity improver, the
stuff that's like pouring honey into your engine and that makes the
oil "thicker". Except instead of putting it into the engine, put it
in the tranny. Make sure the tranny if fully warmed up before you
start adding it and it will take a while to pour it down the dipstick
tube because it's so thick.
This will raise the viscosity of the AT Fluid when it's hot and the
higher viscosity will allow the pump to generate more pressure and
will also reduce the leakage at the various internal seals.
2 - buy a can of Trans-X or some other "transmission seal conditioner
and rejuvenator". To avoid overfilling the tranny look for one that's
pint sized rather then quart sized. Pour that down the dipstick tube.
This stuff will soften and swell the internal rubber seals which will
also reduce leakage internally which will give the pump a better
chance of building up the high pressure it needs to keep reverse from
It will take several days to perhaps a couple weeks for this to do
it's magic, if it works at all. Since we don't really know why it's
slipping, this may or may not help. It will not hurt anything in the
transmission. I have done this routine in several transmissions and
sometimes it helps. It has never caused a problem. You can even dump
in two cans of the "STP" type stuff if you want or feel it might help.
The only thing "bad" about the higher viscosity is that it takes a
little more power to pump it around which means theoretically your gas
mileage could go down one or two percent. You have bigger issues to
worry about then that.
If this does stop the slipping in reverse, then you may get quite a
few more miles out of the transmission. The other thing you can do,
but it's more work, is drop the tranny pan (before doing any of the
above) and change the filter just in case the filter is dirty enough
to be reducing oil flow to the pump which would lower the pressure.
My guess is that won't help, I've never seen a AT filter that had much
stuff on it nor have I ever had a filter change affect how the tranny
shifts felt or how it otherwise performed. Unless the tranny is
actually starting to come apart, there just isn't much to filter in
them. That's why new cars now go 100K on the original fluid and
filter (if nothing goes wrong).
Elbridge Gerry, of Massachusetts:
"What, sir, is the use of militia? It is to prevent the
establishment of a standing army, the bane of liberty. . .
Whenever Government means to invade the rights and liberties of
the people, they always attempt to destroy the militia, in order
to raise a standing army upon its ruins." -- Debate, U.S. House
of Representatives, August 17, 1789
full line pressure insures clutches grip tight. Some cars slip
after a fluid change because grit was " shimming " clutches tight,
now that grit is gone, clutches no longer fully engage.
My advice, add a drain plug, and change fluid frequently,
it takes more than one change out to expel old fluid. My TH350
lasted 180 K miles.
I wouldn't worry aboiut it. My 85 Chevy Caprice has been doing that
(sometimes) for the last 7 years and last 100K. It hasn't gotten any worse
since it started.
OTOH, I had a 77 Ford Granada which started slipping in reverse, and it did get
worse, so I could not back up a hill. But forward gears were always OK.
It's probably a worn out clutch. Unless it blew up into pieces, sometimes
pouring a transmission additive helps. Lucas Transmission fix was mentioned
by several people as being effective. At this point, it's broken anyway, it
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.