AW55-50SN B4 Cover Replacement Fail?

Shoob · Post by **Shoob** » 14 May 2024, 09:40

Hello all,

Been scouring these forums and the wider Internet for the past couple months in a quest to get everyone's favorite AW55-50SN transmission to behave in my 2000 Volvo V70 (P80 platform). After three drain and fills didn't stop it from randomly clunking both during gear changes or while maintaining an arbitrary constant speed, I replaced the B4 servo cover.

This actually made things worse - during the first gear shift from 2nd to 3rd during a drive, the car now loses almost all drive for 1 or 2 seconds and the traction control light illuminates. It only does it the first time it has to perform that shift after a cold start, and never again during a given drive until shut off and left to sit for a little while.

I've resigned myself to likely needing a professional to fix the original clunking issue, but has anyone else experienced the loss of drive and the TCL lighting up on the first 2nd to 3rd shift of a drive after replacing their B4 cover?

Post by **scot850** » 14 May 2024, 11:11

First, sorry to possibly insult you, but did you use the correct transmission fluid? These trans use 3309 rated fluid not the older ATF.

Have you checked the fluid level is correct when the trans is warm?

Several years ago I spoke to the shop foreman on the B4 issue and he said my 00 V70R was not affected by this issue. It also has the 5 speed auto trans.

Neil.

Shoob · Post by **Shoob** » 14 May 2024, 11:26

I did indeed use JWS-3309 spec, Toyota T-IV to be specific. This neither improved nor worsened its behavior before I replaced the B4 cover.

SOURDOUGHJIM · Post by **SOURDOUGHJIM** » 15 May 2024, 05:05

I have the servo cover on the bench to install next time I'm so motivated. But I've noticed I don't really have an issue with the 2-3 upshift when cold. It's much more an issue when using the a/c. Now I'm thinking an auxiliary cooler would go farther in curing this issue than replacing the cover.

dikidera · Post by **dikidera** » 15 May 2024, 05:12

You know clunking can sometimes be caused by worn out mounts, the top one on the head starts having serious play. Then it takes out the one underneath the gearbox.

Another clunking source is a loose CV axle bolt, this creates play between the CV axle and the wheel bearing. Also on my car, I also had special rubber spacers/dampener on the CV axle, which was entirely missing on the other side.

From then on, I would start considering if my solenoids are also not sticking for harder shifts.

Addendumg: For you to be losing drive, I would imagine it's a loss of pressure?

Shoob · Post by **Shoob** » 15 May 2024, 09:22

dikidera wrote: ↑15 May 2024, 05:12 You know clunking can sometimes be caused by worn out mounts, the top one on the head starts having serious play. Then it takes out the one underneath the gearbox.

Another clunking source is a loose CV axle bolt, this creates play between the CV axle and the wheel bearing. Also on my car, I also had special rubber spacers/dampener on the CV axle, which was entirely missing on the other side.

From then on, I would start considering if my solenoids are also not sticking for harder shifts.

Addendumg: For you to be losing drive, I would imagine it's a loss of pressure?

I'll check the mounts and CV axles, I did read that bad or worn out engine mounts can cause transmission problems. I should've been more descriptive though, when I say clunking it's like the car is forgetting what gear it's supposed to be in for a second and the whole car jerks while it clunks/bangs back into the correct one. 99% of a drive is perfectly fine with no weird noises.

Post by **scot850** » 15 May 2024, 10:13

I had this issue very occasionally with my car, particularly when slowing to turn left or right on uphill gradients. I full flush at the dealer seems to have fixed that. I would suggest trying a full flush (requires about 12 liters/quarts of oil). Do not have the trans power flushed.

There is a process on MVS for doing this by removing the inlet pipe to the radiator trans cooler using a clear pipe and then running and topping up the trans several times after draining 2 liters or so. Continue doing this until the fluid runs clean.

I am not a trans expert by any means, but the trans has a certain amount of 'learning'. So maybe the adaptives can be reset and relearned after the B4 change. Hopefully others with more experience can chip in.

Neil.