1980 Chevrolet Caprice: transmission slips in reverse

The transmission seems to slip when going in reverse in my 1980 Chevrolet Caprice (OK going forward). Transmission fluid is OK.
Is there anything one can adjust--or does the transmission
have to be torn apart or replaced to fix? (I assume replacement from the junk yard would be cheaper?)
--
Jonathan Grobe Books
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On Fri, 17 Dec 2004 00:24:02 +0000 (UTC), Jonathan Grobe

afraid it qualify as a "beater car". your's sounds like one too. unless you can backup on a little hill, let it go. stop backing up. ...thehick
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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?
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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 supply.
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 slipping.
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
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Meh. My Celebrity had about 70k on it, and it stopped shifting into overdrive at 45 mph, it would do it at some random later speed. Dropping the pan and changing the filter cured it.
-Sam
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Sam Tosi!!!!@#!! wrote:

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.
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Rebuild is a possibility, no adjustments for that. Problem is the reverse clutch.

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Jonathan Grobe wrote:

Maybe it needs a fluid and filter change. How many miles?
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Paul
'91 XL1200
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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.
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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 can't hurt.

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My trans in my 85 Caprice has been slipping (sometimes) in reverse for about 5 years or so. Never got any worse. It started slipping about 100,000 miles ago. It does leak some trans fluid.
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Rog wrote:

Could be a clogged filter, low line pressure seems to affect reverse clutches more than forward ones. I'd go with new fluid and filter before adding any " tonics "

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