2001 xc70 lost 1st and 2nd gear 3 ,4 ,5 works fine takes off in 3rd

[horizonmkt]

I have owned a 2001 XC70 for probably 12 years started with transmission issues @ 70000. Changed the fluid right away to the recommended mobile 3309 fluid drained and filled numerous times and now I have around 170,000 miles on it in a running in the transmission issues again seems like the seafoam additive Has helped on occasion but recently I lost first and second gear but I found a new way to get it back
I tried forcing compressed air through the top hose going through the radiator and in addition I put a small amount of sea foam in my clear adapter tube and forced it back into the transmission wondering whether the properties in it would help clear the transmission filter Which I found on the forum that somebody else had done.
I'm wondering whether this is the right way to do it the proper hose to put pressure to get to the internal filter on and whether there's some other way or liquid to use to attempt to clean the internal filter which I believe is the problem. Any Ideas? Is this from a solenoid if so which one?
I love the car and everything else works great and would like to fix my self

DON

[AKAMick]

The filter within the transmission is basically a fine screen, when it gets plugged up, the trans of course is starved of fluid and will no longer work, forcing compressed air will dislodge the muck, resurrecting the flow temporarily. I had a Nissan that uses this same AW55n slushbox that the torque converter impeller sprag disintegrated and the debris plugged the screen, I used a compressed air tank a few times to clear the screen just to get it home, The Nissans AW55n was much easier to remove than a Volvo, after removing the trans and confirming the sprag was toast, it spun roughly in both directions which it should only rotate one way, removed the pump housing on the trans and another section exposing the screen, which was plugged with aluminium from the TC impeller, removed it and cleaned it, and cleaned as much debris as possible without getting into an overhaul. The Nissan was not worth the trouble, replaced the TC with a rebuilt which was almost exceeding what i felt the Nissan was worth, reassembled and reinstalled the trans fitted a inline filter and Valvoline Maxlife to fill, dumped and and filled the trans with a inline filter change about 3 times, as opening the inline filter each time, finally showing it was not picking up any more debris. The Nissan was used for a few years until it moved on. The XC70 trans is bit more trouble too remove from the car but the same remedy can apply if the screen is plugged,

[Astro14]

If you have had “issues” for 100,000 miles, I don’t think back flushing the screen is going to do more than get it to move a few miles more. Even with fluid changes, 100,000 miles is a very long time in the life of a transmission.

The 2001 were known for valve bodies that lost their ability to hold line pressure, leading to premature parts failure.

You can’t fix that by pouring stuff into the transmission. Running 100,000 miles with “issues”, likely from low line pressure, and the resultant poor shifting, and it’s very likely this is worn out.

What, exactly, do you think is plugging up that filter? There is only one possible source of debris in the transmission - the transmission itself. So, whether chunks of hard parts, or the frictions from soft parts, if the filter is plugged, the trans is done, not because of the filter but because of the source of enough debris to plug it.

If you’ve lost two gears, then it’s likely not a solenoid, or even a valve body. It’s rebuild time.

[horizonmkt]

Thanks for the info Since you tried it would it be better to blow back thru the top hose or the bottom hose? It did kinda work for me?

[FirstVolvo]

On a different forum you mentioned the transmission throwing a P0762 code, is this still happening?

[horizonmkt]

Yes in a different program it said P0762 Shift Solenoid C - Stuck On Under a Perminate trouble code. no other codes?

[FirstVolvo]

Yes in a different program it said P0762 Shift Solenoid C - Stuck On Under a Perminate trouble code. no other codes?

With this error you will not be able to fix the issue by trying to clean the filter and the filter isn't clogged if gears 3,4 and 5 are working fine.

Your lowest cost fix would be to remove the valve body, disassemble and you find a clog the small screen that supplies fluid pressure to the S4 solenoid or a problem with S4 solenoid itself. This is the solenoid and path I think is causing the problem base on the Sonnax solenoid on/off status table for the different gears. The other option is to replace the valve body with a quality rebuilt one or a new valve body. This is a lower chance there's a TCM problem but I think this isn't a high probability.
The VB replacement can be a DIY job but not for everyone, what helps determine if you want to tackle this job or not is the great write-up link below. I do think the only way you're going to fix this problem is with the valve body and you have to decide on this route based on the condition of the rest of the transmission and the car itself.
If the transmission hasn't been banging into gear or slipping for any length of time the rest of the transmission may still be in decent shape and worth a repaired or new valve body. When you had problems at the 70K mile mark what was the transmission doing and did the fluid change fix it completely until this recent problem?

Excellent valve body replacement how-to by Astro14
https://www.volvoxc.com/0/resources/...ment-Notes.pdf


Edit: I looked at the manual again and I don't think the problem is with the little filter screen for the shift solenoid being plugged up, the filter is before the solenoid so if it were plugged there wouldn't be any fluid pressure to the solenoid.

This narrows the problem to the S4 shift solenoid itself of less likely the TCM always energizing the S4 solenoid, which closes the solenoid and builds pressure to move the shift valves in the valve body.

Below is a link to a messy video of the valve body with the cover off and the engine running. You can see the S4 shift solenoid on the right top (smaller group of shift solenoids) and the fluid coming out of the middle hole. This is what the S4 solenoid should look like when it's not energized, it's a Normally Open solenoid so when it's not energized it's open and the fluid is exhausted through the center hole. In the video you can see the fluid streaming out of this hole, especially at start up. If you were to do the same thing; remove your VB cover and start the car (and IF I'm right) you would see no fluid coming out of the center hole. The S4 solenoid is stuck on, meaning it's always energized and closed or just plugged up but either way it's not exhausting the fluid like it should. To determine if the solenoid is always being energized, which would indicate a problem with the TCM or shorted wiring (long shot) you could unplug the single wiring going to the solenoid and measure voltage on this wire with the other meter lead to ground. With the key on and in Park you should NOT see 12V on this S4 solenoid, it should be off. If you have a geartronic I think you can manually shift to 3rd and see the solenoid turns on/energizes, which would be the correct operation,
It's possible you may be able to fix this problem with just a S4 solenoid swap, if the electrical checks out okay and it's a problem with the solenoid itself.

I remember seeing this video year ago, messy but interesting to watch, at least to me.

https://www.youtube.com/watch?v=8Fvt8Emduek