Shifting from third to fourth under slight acceleration it shudders

FREEBUSINESSES

MEMBER
2003 BMW X5
4.4L
V8
4WD
AUTOMATIC
180,000 MILES

I have an issue which is more annoying than a problem. While just trying to maintain speed at range of forty to sixty mph, the rpm is constantly going up and down 200 rpm's as if pulsating consistently, not erratically. It appears only to happen in fifth gear which makes me suspect the lock up converter is issue. In sport mode I put in fourth at same speeds and no issue, only in fifth. No codes of any kind, just changed transmission filter and fluid and no signs of burned fluid or any evident sludge in pan. Was brown, but it was changed about 90,000 miles ago, so I suspect this would be normal. Now here is another strange issue, when shifting from third to fourth under no only slight acceleration it shudders for a second, as if slipping, but never in sport mode or under regular acceleration. Do not know if problem is connected, but thought I would mention it. Runs perfect otherwise, so any suggestions?

Monday, November 13th, 2017 AT 7:58 AM

3 Replies

JACOBANDNICKOLAS

MECHANIC
110,114 POSTS

This sounds like the transmission input shaft sensor is not working correctly, when this happens it will not set a code here is how you can change it out in the diagrams below.

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

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Monday, November 13th, 2017 AT 5:51 PM

FREEBUSINESSES

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2 POSTS

Thanks, the sensor fixed it all good!

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Monday, November 13th, 2017 AT 6:12 PM

KASEKENNY

MECHANIC
18,907 POSTS

Clearly if someone checked this out and found that these three things are faulty then that would be fine to fix the issue but it sounds like they are just guessing at the different components that you would need to fix this issue.

I doubt this is the idle control as that only regulates incoming air to make sure the engine does not stall. It is unlikely to cause a harsh engagement.

The MAF again is unlikely to cause this as well. Granted if they are not reading accurately then they can cause the engine to run poorly and that may cause the transmission to shift when it should not but if you only have a harsh shift then that again is unlikely.

If you would like to clean it and see if it makes a difference then here is a guide that will help with this:

https://www.2carpros.com/articles/mass-air-flow-service

You have a hot film sensor so they can be cleaned but if monitored then we would know if they are reading correctly. Basically you just watch the Hz or voltage on the signal wire and it should move smoothly up and down as you accelerate.

https://www.2carpros.com/articles/how-to-check-wiring

Where I would start is with the fluid. If this is dirty or low it will cause this issue. So I attached the info on checking the fluid and then we should change it if it is suspect at all.

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Please run through this info and let's go from there. Thanks

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