Hello guys!

It has been a while since I posted here. Some of you have read my thread on the 5HP18 autobox stuff as I overhauled one in 2016. That box is still doing fine, no issues at all.

I am in the process of completely stripping and doing full body restauration on the E34 fitted with that box. I am talking full restauration of the exterior and powder coating the front and rear subframe, overhauled diff etc.. etc...

Since someday I will want a bigger engine, 4.0 or "M60 4.4" custom engine, I will need a stronger gearbox. I will fit a 5HP30 somewhere in 2019 after full body restauration has been done. Naturally, this box will also be completely overhauled.

I will tell you guys globally how this setup will work. This is good info for anyone who has the intention to swap to a different autobox.

1 - Fitment
Generally, since the M60 3.0 and M60 4.0 have the same bolt pattern, the box + converter will fit right away. I will need the original gearbox support piece for the E34 5HP30 but that is easy to find on yards. Fitting the box behind the engine is a matter of wrenching. Now, the 4.0 uses the large case differential and the 5HP30 is longer in length compared to the 5HP18. In sum, I will need an original 540i diff (or at least the large housing) and a shorter driveshaft / original 540i driveshaft. I have that sourced and those items are coming in. Note that the large diff housing uses different shafts to connect to the wheel hubs. The diameter is bigger and they have more bolt holes.

2 - Electronics
The early EGS should fit without any theft system problem. The 5HP18 and 5HP30 chip casing and pin construction is the same which means it will slot right in. HOWEVER, the PIN LAYOUT and the CONNECTOR TO THE GEARBOX is different. I will need an ORIGINAL 540i or 740i cable piece from box to EGS electric box. I will also have to use the electrical documentation to rewire some wires. Not much of a challenge just need to make a clear guide for myself.

3 - Driveability
These electronic gearboxes work on a shift program based on which the EGS sends signals to the solenoids engaging / disengaging the right clutches at the right time. I always thought that the gearbox computer needed to know the exact engine torque / rpm curve to know exactly what it will handle in torque when shifting. On the most modern gearboxes, this is possibly true as these gearboxes have full modular solenoids. However, the 5HP18 and 5HP30 are some sort of a bridge between old school transmission hydraulics, pressure + governor and modern fully modular solenoid shifting gearboxes. Basically, the 5HP18 and 5HP30 need to know the engine load for its shift program. In the past, this was measured with a vacuum line to the engine block and a vacuum modulator on the gearbox housing. Depending on the pressure in the engine block, the gearbox shifts or does not shift based on valves actuated by that pressure. On the 5HP18 and 5HP30, this is no longer directly done with modulator pressure but with electronics. Using the intake manifold pressure sensor, the gearbox computer knows the pressure and engine load. Depending on:
- That engine load
- How far the throttle valve is open
- How much RPM the car is doing
- And some other variables (cornering, temperatures)
The 5HP18 / 5HP30 decides to upshift or downshift.

I was wrong in thinking the 5HP18 and 5HP30 need to know the exact torque / rpm curve thinking engine load was used to decide HOW to shift (sooner / later & more or less pressure). I found out this is not the case. They do not use engine load to decide WHEN and HOW to shift but only WHEN to shift.

So basically, between the old non-electronic boxes and the modern boxes with full modular solenoid action, is the 5HP18 and 5HP30.

This all being said, I think that after fitting all the 540i parts and the 5HP30.. also rewiring the stuff, I should have a perfectly fine shifting 5HP30 behind my M60B30 "little" engine.

The main advantage is that my car is "large V8 ready". Another advantage is that the M60B30 will put only 290Nm on a box made to handle 560Nm.

I will keep you guys updated.