Advice on hard shifting tranny

[mamij]

Hi Guys

I'm trying to track down a possible transmission issue in my car, 735i 2000, 73k miles with the 5HP24 tranny.
I'm experiencing a hard upshift between 3.rd - 4.th gear.
This only occurs when engine is warm (has at least reached the first mark on the temperature gauge after blue portion), NO issues when cold.
Transmission shifts flawlessly between all gears when engine is cold, all gears feel the same, with of course a bit less smoothness due to being in cold program.
Transmission fluid and filter have already been serviced with OEM oil/filter, and the issue was present even before the tranny service, which means no difference after the service what so ever.
I've had this "issue" since I bought the car 6 months ago, but have merely been ignoring it, since a tranny service didn't help.

Scanned the car with INPA, got no transmission error codes.
I do however have an intermittent engine camshaft sensor error for bank 1 and a 0F-8C Map controlled thermostat circuit/control.

Thing I've tried so far:

- Spare OEM MAF (cleaned with CRC cleaner)
- Resetting adaptations with INPA for both engine and for the transmission under the EGS settings
- Unplugging the camshaft sensor (don't know if this is enough to test if the sensor could be responsible for this)

None of these things made any difference, not even resetting the EGS adaptations (I actually expected the tranny to shift like crap after this).

The hard shift feels worse when accelerating faster, this is where I really can feel the hard shift.
If I simply just use a light foot when the shift occurs, it feels almost as smooth as the rest of the gears.

I've been reading up on this a bit on the net, and many posts point to a valve body issue, but since this is a low mileage example, I find it hard to believe, that this could be the culprit.
Also since I don't have any tranny error codes, I don't suspect a solenoid in the tranny being the culprit.

I hope you guys can chime in with some advice

[Timm]

Usually this is an engine problem rather than a gearbox one - and in particular MAF or vacuum leaks - or, bizzarly, whether the A/C works. The problem is that the revs drop too low during a downshift and it cracks into the next gear to increase the engine speed. So, at idle, ensure that the engine revs are at 700 RPM (which will indicate that the A/C system is at least doing something) - and then use INPA to see if there are any vacuum leaks:

[mamij]

Usually this is an engine problem rather than a gearbox one - and in particular MAF or vacuum leaks - or, bizzarly, whether the A/C works. The problem is that the revs drop too low during a downshift and it cracks into the next gear to increase the engine speed. So, at idle, ensure that the engine revs are at 700 RPM (which will indicate that the A/C system is at least doing something) - and then use INPA to see if there are any vacuum leaks:

Thanks for the response Tim.
Now that you're mentioning it, I've actually tried shutting off the A/C system, this also made no difference at the particular shift.
Regarding vacuum leaks, I've tried spraying carburetor cleaner on the engine while it was running, didn't notice any change in RPM, but I'll see, if I can spot something in INPA.

[acspecialists]

Follow Timm's advice. I almost replaced my transmission and the problem was the MAF, buy oem no matter what it costs. You could also do smoke test but INPA is your best bet.

[X3456]

Good info/guidance above!
Better than I could have said and that been my experience.

Sent from my SM-J727T using Tapatalk

[mamij]

I finally had some time to diagnose this "issue" a bit further.
Tim, in relation to your advice, I followed your video "BMW Diagnostics - A better way to Find Manifold Leaks", BUT without removing the blanking plug on the PCV, hope this doesn't change much.

I ran INPA while engine was hot and uploaded the video to vimeo.
I had A/C on all the time, but at an ambient temperature of 22 celcius.



I hope this can prove something.
But again to clarify, I experience the hard ushift from 3.rd - 4.th gear as soon as the tranny is out of the cold program (stops shifting at higher rpm).

Please give me your thoughts when you can.

[kouks]

I’ll agree with Timm if you say you can go through all the gears while the trans is cold and not have a shift “thump”, especially during a hard acceleration. There are two mechanical issues that can cause a thump, one is a valve sticking in the valve body (usually rare) or a gear spring broken in one of the gear drums in the trans (not so rare).

A sticking valve will reproduce itself under specific loads and conditions. In other words, what’s making it stick is specific and it will only occur at certain recognizable times. In the 5HP24 the main control valve has a problem if the car has been driven on the highway at high steady speeds the majority of its life. Since you’re in Denmark and the car has low mileage, I doubt this is the problem, unless you drive to Munich every week at 160km/hr without slowing down.

A bad spring will thump all the time at every shift. It will be subtle during cold operations and really be noticeable in warm operation. It will always happen, every shift into that gear, and will be very noticeable during hard acceleration, cold or hot.

if you don’t have these issues, then continue to track down electrical problems. You can use INPA to activate the control modules in the valve body. With the engine OFF, but the key in the number 2 position, use INPA and activate each of the shift solenoids, you should here a nice clicking sound be each one. If one sounds very weak, that may be your problem.

[mamij]

I’ll agree with Timm if you say you can go through all the gears while the trans is cold and not have a shift “thump”, especially during a hard acceleration. There are two mechanical issues that can cause a thump, one is a valve sticking in the valve body (usually rare) or a gear spring broken in one of the gear drums in the trans (not so rare).

A sticking valve will reproduce itself under specific loads and conditions. In other words, what’s making it stick is specific and it will only occur at certain recognizable times. In the 5HP24 the main control valve has a problem if the car has been driven on the highway at high steady speeds the majority of its life. Since you’re in Denmark and the car has low mileage, I doubt this is the problem, unless you drive to Munich every week at 160km/hr without slowing down.

A bad spring will thump all the time at every shift. It will be subtle during cold operations and really be noticeable in warm operation. It will always happen, every shift into that gear, and will be very noticeable during hard acceleration, cold or hot.

if you don’t have these issues, then continue to track down electrical problems. You can use INPA to activate the control modules in the valve body. With the engine OFF, but the key in the number 2 position, use INPA and activate each of the shift solenoids, you should here a nice clicking sound be each one. If one sounds very weak, that may be your problem.

I've just done the solenoid test with INPA only in ignition.
To me all solenoids seem to click fine, though it seems nr 3 had a bit louder click compared to the others, other than that they practically sound the same.
Afterwards, I went to the section EDS pressure controller valve to test this the same way, and all these seem to sound the same as well.

BTW, I think I accidentally triggered the "Trans failsafe program" by tapping F8 in the EDS settings, an ignition off and on cleared this state though.
The car drove fine afterwards, no issues what so ever, I hope I haven't screwed up anything by simply activating this in the settings?

I seem to still be getting the camshaft error code once in a while, and clearing the code usually keeps the error away for a few weeks.
Can this sensor have any impact on tranny shifts, does unplugging the sensor prove anything?

[georgebest]

I’ll agree with Timm if you say you can go through all the gears while the trans is cold and not have a shift “thump”, especially during a hard acceleration. There are two mechanical issues that can cause a thump, one is a valve sticking in the valve body (usually rare) or a gear spring broken in one of the gear drums in the trans (not so rare).

A sticking valve will reproduce itself under specific loads and conditions. In other words, what’s making it stick is specific and it will only occur at certain recognizable times. In the 5HP24 the main control valve has a problem if the car has been driven on the highway at high steady speeds the majority of its life. Since you’re in Denmark and the car has low mileage, I doubt this is the problem, unless you drive to Munich every week at 160km/hr without slowing down.

A bad spring will thump all the time at every shift. It will be subtle during cold operations and really be noticeable in warm operation. It will always happen, every shift into that gear, and will be very noticeable during hard acceleration, cold or hot.

if you don’t have these issues, then continue to track down electrical problems. You can use INPA to activate the control modules in the valve body. With the engine OFF, but the key in the number 2 position, use INPA and activate each of the shift solenoids, you should here a nice clicking sound be each one. If one sounds very weak, that may be your problem.

Could it be low fluid level in transmission as well?

[Timm]

An intermittent camshaft sensor problem can certainly cause hard-shifts....

[mamij]

Could it be low fluid level in transmission as well?

Fluid and filter was changed with the correct procedure (final level checked when hot) at a local BMW mechanic, who is an enthusiast and also only drives BMW.

An intermittent camshaft sensor problem can certainly cause hard-shifts....

Can I rule it out, if I unplug it at the harness, would this be a bad way to test, if the sensor is responsible for this?

[kouks]

Can I rule it out, if I unplug it at the harness, would this be a bad way to test, if the sensor is responsible for this?

Once the CPS produces an error, it is disregarded by the DME, so unplugging it won't be any different of a test. Does the hard shift happen when you clear the code (bad information going to the DME), or when the code is present (no information going to the DME). In either case, if the shift changes character with the CPS code on or off, then you may well have a CPS failure.

[mamij]

Alright, just a quick update.
I've swapped another camshaft sensor into the engine along with an engine adaptation reset, and just as I expected, this made no difference with the shift unfortunately.
At least I got rid of the intermittent code, as a preventive maintenance.

Once the CPS produces an error, it is disregarded by the DME, so unplugging it won't be any different of a test. Does the hard shift happen when you clear the code (bad information going to the DME), or when the code is present (no information going to the DME). In either case, if the shift changes character with the CPS code on or off, then you may well have a CPS failure.

The hard shift is present all the time, no matter if the code is present or not.
Coming back to what you said earlier, about a sticking valve in the valve body.
I know this car has been parked for most of its life, and driven rarely, hence the low mileage (92 year old owner all its life).

Could this possibly have caused a sticking valve, and would accelerating the car a bit harder unstick the valve somehow (like speeding from 0-100 under WOT a few times) ?

Also read about software updates for the EGS/DME unit, something like this:

http://www.bimmerboard.com/forums/posts/1044830

Would this be worth a shot to eliminate the hard shift, as I already own the SSS Program v32?
Is the latest software available for the e38 in this program?

[mamij]

I’ll agree with Timm if you say you can go through all the gears while the trans is cold and not have a shift “thump”, especially during a hard acceleration. There are two mechanical issues that can cause a thump, one is a valve sticking in the valve body (usually rare) or a gear spring broken in one of the gear drums in the trans (not so rare).

A sticking valve will reproduce itself under specific loads and conditions. In other words, what’s making it stick is specific and it will only occur at certain recognizable times. In the 5HP24 the main control valve has a problem if the car has been driven on the highway at high steady speeds the majority of its life. Since you’re in Denmark and the car has low mileage, I doubt this is the problem, unless you drive to Munich every week at 160km/hr without slowing down.

A bad spring will thump all the time at every shift. It will be subtle during cold operations and really be noticeable in warm operation. It will always happen, every shift into that gear, and will be very noticeable during hard acceleration, cold or hot.

if you don’t have these issues, then continue to track down electrical problems. You can use INPA to activate the control modules in the valve body. With the engine OFF, but the key in the number 2 position, use INPA and activate each of the shift solenoids, you should here a nice clicking sound be each one. If one sounds very weak, that may be your problem.

I drive on the highway once a week, and our speed limits are 130 km/h, and at this point I usually set the cruise control at 135 - 140 km/h, as the speedo always is a bit inaccurate.
I suppose this pattern wouldn't be a problem for the 5HP24 regardless of the length of time at this speed, or are these just super weak trannys for normal highway speed?

[kouks]

I drive on the highway once a week, and our speed limits are 130 km/h, and at this point I usually set the cruise control at 135 - 140 km/h, as the speedo always is a bit inaccurate.
I suppose this pattern wouldn't be a problem for the 5HP24 regardless of the length of time at this speed, or are these just super weak trannys for normal highway speed?

No, the 5HP24 does very well at highway speeds, and at basically at the US 70 mph, it should be fine. Especially since You can't drive too far in Denmark without slowing down.

See if you can get a MAF from a junk car and try that if it helps. You may also try replacing the EGS with another one from a junker car of the same year.

If the thump is there all the time, no matter what the CPS code says, then the CPS should not be the problem.

Driving the car harder will not help if there is a sticking valve. However, you may try to push the car hard once and see if the thump changes character. If its a very hard thump, then you may have a broken gear spring, and the tranny needs rebuilding. Lots of $$$. However, I just can't see how a low mileage car from a older man can fail that early, unless it was abused by his son.

Try the MAF and EGS first and see if that helps.

[mamij]

No, the 5HP24 does very well at highway speeds, and at basically at the US 70 mph, it should be fine. Especially since You can't drive too far in Denmark without slowing down.

See if you can get a MAF from a junk car and try that if it helps. You may also try replacing the EGS with another one from a junker car of the same year.

If the thump is there all the time, no matter what the CPS code says, then the CPS should not be the problem.

Driving the car harder will not help if there is a sticking valve. However, you may try to push the car hard once and see if the thump changes character. If its a very hard thump, then you may have a broken gear spring, and the tranny needs rebuilding. Lots of $$$. However, I just can't see how a low mileage car from a older man can fail that early, unless it was abused by his son.

Try the MAF and EGS first and see if that helps.

I've already tried a spare MAF which is mentioned in my first post.
Also did a DME update, no change.
I haven't had the chance to try another EGS yet.

However, I did try pushing the car from 0 - 100 mph for the first time ever since I bought it, and all the shifts were nice and smooth in this case, shifted from 1st - 4th with no hesitation, no hard shifts what so ever. Driving the car normally afterwards, I've noticed the hard shift behaving just as usual 3 - 4th gear.

Does this prove anything, seems kinda odd to me, that the shifts are completely fine under hard acceleration?