[BmwBk35i]

So Recently i got back my 235i from bmw for a trans replacement and this was shortly after i had installed my jb4... Would you say the jb4 was the issue ?
AKA Drivetrain malfunction

[Benandluna]

How many miles? I know the jb4 is reliable but not sure how it stands the test of time

[BmwBk35i]

i would say i had my jb4 in for about 1k miles pretty sure less than that
and my tranny went via drivetrain malfunction

[Benandluna]

Originally Posted by BmwBk35i

i would say i had my jb4 in for about 1k miles pretty sure less than that
and my tranny went via drivetrain malfunction

That said im curious about others. I know some people have had misfortunes with JB4( not many ), though not sure if any have had a tranny destroyed.

No issues getting it fixed under warranty eh?

[amw896]

wow....manual or auto?

[BmwBk35i]

It's auto

[Benandluna]

Originally Posted by BmwBk35i

It's auto

Wow thats surprising. There are a lot of JB4 users here. not sure why no one is responding with their issues and miles. I would assume your car maybe had a lemon of a tranny.

[allthatisntnow]

Ive got over 4k on the 8AT with the JB4 and haven't had any problems. Darkie, Luminous etc are running Pure stage 2 for well over 10k miles combined without any issues. Probably just unlucky. If the transmission is going to fail due to power handling it'll be the clutch packs that go first. Thats what the torque handling rating is based on and is the weakest link. So you'd be encountering slippage long before it would stop working. You'd more than likely lose your driveshaft before you got any shearing of components in the box. Only thing that would change that would be excessive heat build up (never heard that being an issue, temps are stable @ 83C max for spirited road usage for me) or an oiling issue.

Driveline stress even at 600nm+ isn't going to be much higher than stock as its entirely dependant on the tyres ability to put it on the road. Wheel spin = no additional loading on the drivetrain. So provided you don't run wide racing slicks and torque brake from a stop, the risks are pretty low. You may only get 100000 miles out of the engine and transmission running tuned vs 150000 stock before problems start, but thats a pretty good tradeoff in my book.

Did they say specifically what had gone wrong with it? Could just be an electrical issue that wrote it off and required a swap.

[leeadam]

as someone else mentioned the clutch would go first. On my previous car a 330d e92, i had a remap to 300bhp. after 3k the clutch started to slip, then a whining noise, i had to have new clutch and gearbox bearing had gone. This was on a manual, and never heard anyone with probs on the autos of same car.

[Anthony235]

I can't imagine this is a JB4 issue. Jb4 does not interact with tranny in any way.

If it's a matter of power then that's not jb4's fault (directly).

[Jeff@TopGearSolutions]

Not trying to protect jb4 because we sell them but I doubt it was the jb4. 10's of thousands of jb4s on the road without a hitch.

Likely just bad luck.

[Luminous]

Guys this guy blew his tranny because he was/is running the jb4 with the dinan piggyback, a huge no no.

[Luminous]

Here's the pic he posted showing both piggybacks.

[BmwBk35i]

Uhhh no i blew my tranny riding first gear for bubbles for a year...

[BmwBk35i]

oh and downshifting dont forget the downshifting

[Luminous]

Originally Posted by BmwBk35i

oh and downshifting dont forget the downshifting

I have 48k miles on the car, been tuned since 3k miles. Currently pushing 550whp with countless hard launches for drag events, zero tranny issues. I hope you remove one of the piggybacks, good luck bro.