2001 325xi transfer case/transmission question

**antonioseet** · 04-07-2016, 01:28 PM

Hey guys, I just bought an automatic 2001 325xi from someone who crashed the passenger side wheel and axle. He took it to a mechanic to have the whole passenger side (wheel and axles/control arms/tirods) rebuilt.

He ended up selling it because the mechanic told him that the transfer case needed to be replaced.

So when i went to go see it, the car was in great shape inside and out, the engine starts and sounds great, but when i put it in gear, it pulls very very slightly.
I rev it in drive and the car just acts as if it's going to pull away but it does not, it just moves a very small amount and never really catches. same in reverse. and when i put it in park, it still rolls when i push it.

My question is: do you guys think it's the transfer case, or is it the transmission? I'm okay with doing a replacement of either because i got it pretty cheap, but if anyone thinks its one or the other i would greatly appreciate the help.

If you need more info please just ask. Thanks for your time!

**dhurley34** · 04-07-2016, 02:56 PM

The way the transfer case works is both the front and rear axles must have resistance against each other for it work. Meaning you cant remove the front drive shaft and turn it in to a RWD car. The planetary gears inside the transfer case will just spin. I would jack up the front end and make sure you cant spin (1/8-1/4 turn is normal) the front driveshaft when it's in park. If you can, then the TC is blown. If it all doesnt move, then I would suspect the transmission. Make sure the front axles arent broken either.

**antonioseet** · 04-07-2016, 07:37 PM

Originally Posted by dhurley34

The way the transfer case works is both the front and rear axles must have resistance against each other for it work. Meaning you cant remove the front drive shaft and turn it in to a RWD car. The planetary gears inside the transfer case will just spin. I would jack up the front end and make sure you cant spin (1/8-1/4 turn is normal) the front driveshaft when it's in park. If you can, then the TC is blown. If it all doesnt move, then I would suspect the transmission. Make sure the front axles arent broken either.

I jacked the car up and the front wheels spin freely when i put it in park and the front axles look fine.

**dhurley34** · 04-07-2016, 08:10 PM

With the front wheels only in the air, try and spin the front friveshaft, not the wheels and report back.

**antonioseet** · 04-08-2016, 01:34 AM

Originally Posted by dhurley34

With the front wheels only in the air, try and spin the front friveshaft, not the wheels and report back.

The driveshaft seems to spin fine when the wheel spins.
I'll make a video tomorrow and link it.

**dhurley34** · 04-08-2016, 08:27 AM

In theory the front driveshaft should not spin. I may be wrong, I'll test on my own XI later this evening.

**daytonatrbo** · 04-08-2016, 09:29 AM

With the transmission in park and the rear wheels on the ground, you should not be able to spin the front driveshaft.

So unless the output shaft of the transmission is broken, the issue likely lies in the transfer case. You can get them on ebay around $250 plus freight.

**91e34M5** · 04-08-2016, 12:09 PM

Originally Posted by daytonatrbo

With the transmission in park and the rear wheels on the ground, you should not be able to spin the front driveshaft.

So unless the output shaft of the transmission is broken, the issue likely lies in the transfer case. You can get them on ebay around $250 plus freight.

I tend to agree with Daytona....either a broken shaft or possibly the chain within the transfer case.
Good info on the transfer case in this link. It's for an X3, but they're pretty much the same unit as an e46.
https://www.scribd.com/doc/249645581...r-Case-service

Edit: It's really important in iX's and and any X-drive BMW that all the tires match, be of the same size, and be routinely rotated. The transfer case in these vehicles are very sensitive to tires that don't size match front to rear and side to side and will fail if driven for long periods with tires that are not size matched. Generally the first thing to go will be the nylon composite gear within the actuator. However, the vehicle can still be driven if the actuator fails.

**daytonatrbo** · 04-08-2016, 12:13 PM

Originally Posted by 91e34M5

I tend to agree with Daytona....either a broken shaft or possibly the chain within the transfer case.
Good info on the transfer case in this link. It's for an X3, but they're pretty much the same unit as an e46.
https://www.scribd.com/doc/249645581...r-Case-service

^ that's not quite true. The e46 did not get xDrive. There is NO actuator in the transfer case. And its all gears NO chain.

The e46 got the NV124

**dhurley34** · 04-08-2016, 12:18 PM

The only problem I see is that the TC is 100% constant mesh gear driven. It either works or it doesnt. Without catastrophic failure, I'm not sure how it would just stop working. Severely worn gears are a possibility but I would think it would bang around under throttle regardless. How many miles are on it? I would try and drain the TC fluid and see what comes out.

**daytonatrbo** · 04-08-2016, 12:21 PM

Originally Posted by dhurley34

The only problem I see is that the TC is 100% constant mesh gear driven. It either works or it doesnt. Without catastrophic failure, I'm not sure how it would just stop working. Severely worn gears are a possibility but I would think it would bang around under throttle regardless. How many miles are on it? I would try and drain the TC fluid and see what comes out.

Hard to disagree with that. They are known for seizing up due to the paltry amount of fluid contained and its tendency to leak. I'm not sure I've heard of one breaking internally. But that's not to say it couldn't happen.

**dhurley34** · 04-08-2016, 12:29 PM

If it is something broken or severely worn inside, I would put my money on the planetary gears. The OP says it acts like it wants to move, but barely does. This would lead me to believe there is mechanical failure somewhere between both output shafts and the rotational force is at least attempting to get the rear wheels moving.

Or its the trans lol.

**91e34M5** · 04-08-2016, 01:29 PM

Originally Posted by daytonatrbo

^ that's not quite true. The e46 did not get xDrive. There is NO actuator in the transfer case. And its all gears NO chain.

The e46 got the NV124

Pardon me for the mis-information. My BMW education continues.

**91e34M5** · 04-08-2016, 01:36 PM

Correct me if I'm wrong, (it's already happened), but if the vehicle rolls while in park, and the input shaft from the trans to the transfer case is stationary when rolling, then it would just about have to be the transfer case. If the input shaft from the trans turns when rolled in park, it would be the transmission.

**daytonatrbo** · 04-08-2016, 02:29 PM

Originally Posted by 91e34M5

Correct me if I'm wrong, (it's already happened), but if the vehicle rolls while in park, and the input shaft from the trans to the transfer case is stationary when rolling, then it would just about have to be the transfer case. If the input shaft from the trans turns when rolled in park, it would be the transmission.

If I followed that, yes you are correct. But where the tcase is married to the trans, it's hard to tell what exactly is and is not moving.

**daytonatrbo** · 04-08-2016, 02:29 PM

Originally Posted by 91e34M5

Pardon me for the mis-information. My BMW education continues.

No problem. Hope I didn't come across wrong.

**daytonatrbo** · 04-08-2016, 02:30 PM

Originally Posted by dhurley34

If it is something broken or severely worn inside, I would put my money on the planetary gears. The OP says it acts like it wants to move, but barely does. This would lead me to believe there is mechanical failure somewhere between both output shafts and the rotational force is at least attempting to get the rear wheels moving.

Or its the trans lol.

Could be sheared splines, anywhere in the equation.

**antonioseet** · 04-09-2016, 12:51 AM

Sorry I didn't come back with any information today, i was crazy busy at work. but tomorrow i should have more time to highlight and make a video of what you guys are proposing.

1. Place the car in park and roll it
2. go through the gears and see what happens.
3. Jack up the front and check the driveshafts
4. while jacked, go through the gears to see if the wheels move at all.
5. drain the TC fluid.

If i were to take out the transfer case, would i be able to see if it's the cause?

anything else you guys would like me to report on?

**dhurley34** · 04-09-2016, 10:40 AM

Check the front drive shaft, not shafts. The one that goes from the TC to the front diff.

**antonioseet** · 04-09-2016, 12:01 PM

Originally Posted by dhurley34

Check the front drive shaft, not shafts. The one that goes from the TC to the front diff.

Can you find me a picture of the drive shaft you're talking about???

Edit: I think i found a picture of it online. Will i have to take stuff off or will it be exposed?

**dhurley34** · 04-09-2016, 01:00 PM

You'll have to remove the belly pan covers. The shaft is on the drivers side.

**antonioseet** · 04-09-2016, 04:17 PM

Okay so the drive shaft moves when going through gears! here is the video: https://www.youtube.com/watch?v=pvN_vQ7XuAI

When it goes into park it makes a weird grinding noise and it sounds like air is escaping from somewhere.

**Doge** · 04-09-2016, 04:21 PM

Video is set to private.

**antonioseet** · 04-09-2016, 04:24 PM

fixed, new link.

**dhurley34** · 04-09-2016, 04:30 PM

The front driveshaft is moving but the front wheels are not however i cant see the passenger side to see if its spinning. If neither wheel spins when the driveshaft spins then the front diff is bad if the axles shafts are ok. The TC is functioning as designed.