Transmission shifts abruptly from 3rd to 4th

[laguner]

My transmission shifts fine in all gears up and down except upshifting from 3rd to 4th gear. If I am accelerating hard there is much less of an abrupt shift but if lightly applying the throttle the shifting from 3rd to 4th is abrupt. Any ideas? I have a brand new driveshaft and transmission mounts. The problem does not change with temperature. My car was produced in December of 89 and is a 535i with the 4HP22EH transmission.

[632 Regal]

have you started changing the fluid gradually and changing the filter?

[laguner]

I have the stuff. I will change the filter and fluid this week but I highly doubt that is the issue since all the other gears work fine.

[Alexlind123]

I had a bit of the same problem, it went away with a fluid/filter/gasket change for awhile, then it sort of came back. Its only abrupt for me if i am accelerating hard up a hill when it shifts to 4th. I would check your fluid level, i have a small leak that i have yet to track down so its sort of hard for me to keep the level right. I think the level may be the main cause of mine, even if it is within the lines, it should be at the top line when warm, i think. If my level is right at the line instead of partway through the problem goes away completely.

[laguner]

My fluid is at the top but I'll recheck it.

[Alexlind123]

be sure to check it with the engine running and the transmission warmed and in park.

[632 Regal]

ahh... warmed, can still hold the hand on the pan, not burning hot not too comfortable.

[pundit]

Mine does exactly the same thing.
I have changed the fluid three times in about six months.
After the change it shifts beautifully for a couple of days and then over about a week it winds up back with the good old hard shift into top gear again.

So the fluid change definately makes a difference... but only a temporary one!

[willobmw]

Ever consider using a Synthetic? I'm using Mobil 1 in the tranny and for power steering fluid. Tranny is shifting smooth. Either that or I'm driving too fast for it to complain. Don't you guys create a pandemic on 535i slush boxes now.
Willobmw

[Alexlind123]

On some days mine shifts better than others, i attribute this to the fact that my transmission leaks and the level fluctuates slightly (but always between the lines). I will try synthetic on the next change. Some days i can discern each shift, other days i have to be looking at the tachometer to tell when it shifts. The 3rd to 4th is always the first to be harsh though perhaps its the first to notice a slight variation in fluid level. Maybe i should try over-filling slightly too see what happens... Also, its not really a pandemic, its just a particular quality of 535iAs, albeit not a very desireable one.