[SyNtAxx]

Hey all,

I'm wanting to tune my bone stock 08 335xi with 57k miles on it. I have the 6AT in it. I've not been able to find hard numbers on what the 'safe' limits of the XI/6AT setup is.

I was looking at MHD with the OTS maps. I'm assuming the car/trans/xfer case can handle all the way up to FBO/Stage 2+ ?

I'm not looking for a tuning war or vendor war. Just an an answer and preferably some numbers to go by HP/TQ *shrug* as I said Im new to the car...only have 3k miles under my belt in her.

Thanks,

Nick

[ewicky]

Short answer: Keep adding power until the tranny begins to slip. From what I've heard, probably around 500-550 HP, but with age that could be lower. 57kmi is the perfect time to drain&fill the transmission, as well as replace the pan/filter (if it hasn't been already). xHP claims to be able to squeeze a little more out of these trannies before slipping by immediately applying max available pressure to the clutches.

The AWD system, as far as I've heard, isn't really an issue. The rear end and AT are the same as RWD, so that's solid. AWD adds front drive shaft, diff, two half axles, and the transfer case. I feel like the transfer case will just slip before a surge of power could make it thru strong enough to grenade the diff or snap shafts. I've heard people mention that the transfer case is under-spec for the application, but I've understood that's inherent to the car and not the power levels. Specifically, it's the massive torsional surges that occur when ABS/DSC kicks in. Failure rate compared to how many cars on the road, I'd say xDrive, ZF6, and the e9x rear end are all remarkably robust. Even more so when you service appropriately and ignore the "lifetime fluid" claim BMW made from the factory.

Also, drain and fill the transfer case. And diffs. These parts age like 50x faster when the friction modifiers in the oil get all worn down. So never let the oil get that old.

[cgbimmer]

Hey bud these cars can do mhd 2+ no problem. I am only running stage 2 xhp tranny flash but helps match the shifts better with mhd..
They are compatible together.. I think when you get over 550 hp could give issues if you launch a lot.. But I would change the tranny fluid and pan/filter with that mileage and transfer case too.

[buster84]

I'm running at least 600hp and I havnt noticed any slipping of the transmission (but its not stock, its flashed) or other issues. So far the only thing I had to replace was the front axel and that wasnt because of it being broken but the boot breaking causing the oil to go everywhere. The previous owner took alot of care of the car before I got it and he changed all the fluids often which helps keep it going strong. These x-drive models can handle alot of power, just dont expect to launch it at 5k+ rpms from a stop. Maybe the biggest reason my car is doing great is that I dont track it and I dont floor it hard from a stop.

[SyNtAxx]

Thank you all for the input....I will take a look at flashing then I appreciate the feedback.

-Nick

[l3rett]

Originally Posted by SyNtAxx

Thank you all for the input....I will take a look at flashing then I appreciate the feedback.

-Nick

Take a look at XHP for tuning the tranny. Very worth it to make the most of your engine tune. I also just got xDelete and opened the clutch in the transfer case to make my xDrive a RWD. It's simple to switch it back when the weather gets bad. It's fun to spin the rear wheels in second gear. And the car just drives a bit more lively, though not quite as sure footed. Feels more like a cheetah and less like a mountain goat.

I'm running MHD 1+ (no downpipes yet) 93 octane map, stage 3 XHP with slightly modified shift points and xDelete on a 2011 e92 with 265/35R18 on the rear and they'll spin through second gear. I've run the e50 and e30 maps and they are a beast, but I don't have a good source for e85.