Volvo 2.5T AWD 2003 Automatic delay 3 to 4

[greffel]

If think I will stop chasing this problem.... next step would be a good used gearbox from the yard.
To get to the possible internal leak is not for a normal skilled home mechanic ?

[firstv70volvo]

If think I will stop chasing this problem.... next step would be a good used gearbox from the yard.
To get to the possible internal leak is not for a normal skilled home mechanic ?

If you're planning on doing all the work yourself and replacing your current transmission with a good used one I will say you have the skills to split open the case of the transmission and replace many of the parts that are likely causing your 3-4 flare. I suspect it's worn 4-5 clutch frictions or a pressure drop due to a leak in the 4-5 apply fluid circuit which includes 3 sealing rings. For the 4-5 clutch apply the fluid enters through the end of the transfer shaft with a sealing ring on the end of the shaft. The fluid then exits through the shaft into the 4-5 drum and there's two more sealing between the drum and the shaft. The sealing rings are hard nylon/teflon type rings and used in different places within transmission. If any of these seals were leaking then there will be a drop in the clutch apply pressure. They're easy to replace when the transmission is apart.
The friction plates are not difficult to replace either. Replacing the seals for the apply pistons is a little more involved because you have compress the springs to get the retaining rings off and pistons out. Replacing shafts bushings is a little tricky if required but doable. There's also possible case wear which would require machining and an insert.

The challenge with a used transmission is finding a known good one and one that's compatible, which depends on the final drive ratio and if it's a FWD or AWD, plus there are changes to the wiring harness connections from 2005 on I believe. If you can find a good used one it's definitely does save time and labor over rebuilding one but if the used the transmission isn't a good one or isn't compatible for some reason and you have do it all over again then I think it's more work than repairing your current transmission.

These two seals are for the 4-5 fluid apply pressure.

There's a sealing ring in the case for the end of the shaft (not shown) where the fluid enters the shaft for 4-5 apply

4-5 drum with clutch that's applied for the 3-4 shift, applied in 4th and 5th gear

[Bramvolvo]

hi my name is bram from holland, i have the exact same problem with my volvo xc70 2001. It shifts perfectly only a shift flare from 3 to 4. my automatic transmission was overhauled 3 years ago, with a rebuilt valvehouse. To try and get rid of the shift flare I replaced the valve house with an original new one, to no avail. I also reset the adaptation values, no result. Well after reading 12 pages I really hoped that you knew the solution, but alas. my gut says you were very close to the solution. Have you tried with a longer B4 valve to see if that helps? I have also flushed the box with mobil 3309, no results there either.

[greffel]

If you have the exact same kind of flare I guess you are out of luck. Does your's feel like a delayed engagement and not a slip?

I did not try the longer pin, but I would gladly invite you to try it