Reverse hard engage and shudder.

[jsrnsis]

Recently, my 1994 850 automatic has developed a hard shudder when in reverse.
It has 112k miles on it, and no history on if fluid has ever been changed.
It began as a shudder in reverse when the engine had warmed up, then started happening when the car was cold. If left in reverse, with the foot on the brake, you can see the engine lurching as the transmisison seems to be slipping. The car still crawls backwards, but as soon as I give it gas it starts shuddering, and even more recently shuddering when it stops at the end of my driveway.
Transmission mount, lower mount by the crank, and upper torque bushing have all recently been replaced.
I did three drain-and-fills using dex3, but the car was up on ramps so I just ran it through the gears with the car running a couple times, leaving it in reverse a little longer just to see how it was doing, between each drain.
After the three drain-and-fills, the car had a very slight clunk into reverse, but no lurching or slipping, and drove fine for a couple days, then the problem started again, with slightly less violent lurching.

The fluid was initially brown, not very viscous, but did not smell burnt. After three drain and fills and driving it to work for a couple days, the fluid is definitely not bright red, and is still a little brown. I'm wondering how much the old fluid could really be affecting the car.

I've searched the internet and found a lot on this topic, but not very conclusive results. Similar to my search to find out just how compatible the different ATFs were, as the only "dex3/mercon" I could find was FRAM fluid at $22/gallon. I'd like to keep doing drain and fills until I'm at 99% replaced, without the shock to the system of a flush, but I can't really afford that.

[MoVolvos]

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Please look at my post for transmission fluids in the linked thread. Double and triple check your fluid level. My 98 S70 T5 had coffee with silver tinge and around 230K miles when I purchased it. Did a full flush or 12 quarts and ran great for a year and got dark again. Did the same 12 quart flush and all was well but donated before next change due to rear main leak.

viewtopic.php?f=9&t=97040

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[MoVolvos]

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I've used the MaxLife years ago and it was not very smooth for a Toyota transmission that was around 250K miles.

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Again, same principle for a flush. IPD sells a kit for flushing, His S80 has the new green plastic clip while yours should be a metal clip that needs to be spread like my 98 I believe. Some cars have upper hose trans fluid out while others are lower hose. Haven't had the 98 S70 for around 8 years so double check yours before proceeding.



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[jsrnsis]

I could check the dipstick again, but we did check, and measured what came out and what went in. More came out the first drain than the other two, almost a full gallon compared to 3.5 quarts, but that might have been because the fluid had such a low viscosity.
I forgot to mention the plug also had no mental on it, just some built up sludge.

I've been wary about a flush since I've read a lot of people saying it's not good for a high mileage car, so I've been sticking to the dex3. Also since I know that's what it's supposed to be and the world of other options is too overwhelming.

[MoVolvos]

I could check the dipstick again, but we did check, and measured what came out and what went in. More came out the first drain than the other two, almost a full gallon compared to 3.5 quarts, but that might have been because the fluid had such a low viscosity.
I forgot to mention the plug also had no mental on it, just some built up sludge.

I've been wary about a flush since I've read a lot of people saying it's not good for a high mileage car, so I've been sticking to the dex3. Also since I know that's what it's supposed to be and the world of other options is too overwhelming.

Metal shaving is rare unless the parts are damaged. Sludge is normal however.

You have to be be sure it is not low! When I replaced the transmission filter and put in a TransGo Shift Kit on my 03 S80 T6 there was a shuddering problem in first and second and I check the dipstick 3 times till I discovered it was low on fluid. No shudder after that. Take it out for 20 minutes to bring it up to operating temperature then check on level ground. Must be sure you are looking at it clearly and correctly.

I have not read a person who wrote a flush damaged a friend's or their own transmission. It is always I heard. Yours could be the first one but it was probably going to fail sooner or later. Done too many flushes to consider it a problem. After 3 full drain and fills you got a lot of contaminated clean fluid or less dirty fluid. Analogous to diluting muddy water by pouring in new rather than pouring it all out and replacing with fresh water.

Again, check the fluid level to help with the reverse issue and if it does not work you've got a problem, which may or may not be solved with a full flush? At that point you have to take an educated calculated risk/guess for further damage by doing nothing or potential fix or damage with a full flush.

As for the DEX III? Only compatibles now as it has been discontinued. The newer synthetics are better fluids and backwards compatible.

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[jsrnsis]

Metal shaving is rare unless the parts are damaged. Sludge is normal however.

You have to be be sure it is not low! When I replaced the transmission filter and put in a TransGo Shift Kit on my 03 S80 T6 there was a shuddering problem in first and second and I check the dipstick 3 times till I discovered it was low on fluid. No shudder after that. Take it out for 20 minutes to bring it up to operating temperature then check on level ground. Must be sure you are looking at it clearly and correctly.

I have not read a person who wrote a flush damaged a friend's or their own transmission. It is always I heard. Yours could be the first one but it was probably going to fail sooner or later. Done too many flushes to consider it a problem. After 3 full drain and fills you got a lot of contaminated clean fluid or less dirty fluid. Analogous to diluting muddy water by pouring in new rather than pouring it all out and replacing with fresh water.

Again, check the fluid level to help with the reverse issue and if it does not work you've got a problem, which may or may not be solved with a full flush? At that point you have to take an educated calculated risk/guess for further damage by doing nothing or potential fix or damage with a full flush.

As for the DEX III? Only compatibles now as it has been discontinued. The newer synthetics are better fluids and backwards compatible.

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I'm going to try some more drain and fills, and run the car more between trys. I'll definitely be sure to pay even more attention to the fluid level, and if this doesn't work I'll try a flush with better, newer fluid. I have hope since it worked before, even though only briefly. I'll post an update when I'm done, I might drive it for a couple days(with a new washer each time) between fills, but I'll keep checking back here, maybe someone has fixed this reverse problem. The engine tried to twist out of it's mounts, it's pretty concerning.

[jsrnsis]

Update:
Fourth drain and fill after a couple of days, fluid had mixed and was a very brownish red, and had no stink.
Before doing the fourth drain and fill, the transmission was slipping and vibrating as bad as ever, my tachometer is a little broken so I couldn't get exact numbers, but in reverse RPMs dropped slightly, but not much. Sport/eco/winter switch made no difference. Vibration didn't matter if car was moving, brake was on, or brake engaged and revving.
Between the two drain and fills I did yesterday, I ran through the gears, and then using a new washer and tightened plug, drove it, including some highway driving. The fluid coming out on the second drain and fill (fifth total) was still very viscous and still very red.
Driving it back and forwards, I couldn't get the vibrations to start again, and reverse always crawled back. No noticable roughness when idle in reverse, no roughness when backing up.
The only problem is the transmission is noticably slipping when accelerating in reverse, engine just revs and then suddenly engages and I'm going 15mph backwards, but with no harsh clunking.