I haven’t found a build other than the X5LM, and mine, with a manual, that has AWD.

Have you found any? I am very curious to know if there are any other builds.

I see. Nope, don't know of one.

I think though, I have reached the limit with the gearbox.

After that 3rd gear pull, I attempted to lazily shift into 4th since there was no need for further acceleration. And the synchros were an issue. I was gently putting into 4th, so no damage. But there was a very light grind, so I just went neutral.

I think that pull spun the box up a bit to hard. I’ve never had grind on any gears on my E53.

So I think it will now require conservative shifting, and being very careful with the redline pulls. I don’t see mildly aggressive shifting below 5000 rpm being an issue, but caution should be used above that.

Those headers really brought the power out. I am still kind of shocked. But at least I learned some limitations, and I know for me personally, there is no reason to be ripping that hard.

I doubt that you're putting out too much power for a ZF320. BMW shipped them behind some pretty torquey diesels with no issue.

The RMS kit puts 400 hp to the flywheel. That was on 91 pump gas.

Add the headers, E85, with meth injection, I wouldn’t be surprised if it over 450. There is a LOT of torque.

Also, remember the differences between diesel, and non diesel engines. The redline on the diesel is substantially lower, resulting in lower input shaft speeds vs non diesel.

It doesn’t take much to blow a gearbox that is out of synchronization, in a high rpm shifting situation. It’s not so much the applied torque that is the concern, unless it is just stupid high on a gearbox that weak to extreme torque.

I am pretty sure I spun the crap out of the synchros. I will NOT be doing that again!

People are running a hell of a lot more than 400 at the crank through the ZF320. Remember that the ZF 5 spd is the go to box for forced induction E36 and E46 M3s because it'll take a lot more abuse that the Getrag 420g.

True, but those applications aren’t over 2 ton, and are not AWD. It takes a bit more to move these tanks. And when you’re pushing them as hard as I did yesterday, I think a bit of caution would be prudent.

Thank you for the heads up on the durability info for the ZF. I’ve always wondered if they were reliable. It just the weight of these vehicles, it makes things work a bit harder, and hotter.

With a manual transmission, it doesn't care of the weight of the vehicle. Only the torque produced by the engine matters. The transmission encounters the same stresses when transmitting X lbft of torque, whether the car is 1,000lbs or 8,000lbs. (Except when it comes to overheating, but that is generally not how manual transmissions break.)

So if I am understanding you correctly, you are saying the applied stress on a drivetrain to move a vehicle, is the same at 8000lbs, as it is for 1000lbs?

The X5 may be heavier, but I suspect that 600-1,000 at the wheels more than offsets the weight.

As I understand it, the weak point is that you start breaking third gear.