6HP26 Rebuild Advice
So, long story short I have bought a ZF6HP26 gearbox from a BMW Breaker for cheap, and I'm intending on rebuilding it. This gearbox is going into an E60 535D that is also mapped, which is quite possibly the worst case scenario for this gearbox as the torque causes major stress on these gearboxes.
I want to rebuild this gearbox, whilst keeping it cost effective, so that when I put this gearbox in I am essentially putting a 0 mileage gearbox into this car and from then on I can maintain it the way they are supposed to be maintained.
Currently the gearbox thats in my car has torque converter slip, and primarily slips in 4/5/6th gear which is on the E clutch, basically that clutch, bushing and torque converter is likely toast, my reverse gear also takes about 2 seconds to engage, things like engine braking has noticeable throttle blips from the torque converter, etc. So I'm not bothering with rebuilding that gearbox as I believe it's long gone + I do need the car to be driving so swapping a built one in is more logical.
This is where I want advice; to buy all the parts, genuine ZF, every last one for a full rebuild + better parts as I will be using a sonnax zip kit aswell, is about £1250, not including the price of the torque converter refurbishment. This includes: Refurbished Valve Body w/ Solenoids: £275, Bushing Kit w/ Pump Bushing: £160, Sonnax Zip Kit: £185, Clutch Packs: £175, Full Rebuild Kit (Rubber Seal Things): £180, 10L Oil & Pan: £270.
Now I'm not a gearbox expert, but from what I can see here's the condition of my own gearbox;
Clutch Pack E which is the main problematic part of these gearboxes, basically no wear, there is slight burning around the outside of the very first clutch, and 1 or 2 minor burn marks on the first steel plate. The rest of the pack is like brand new, nice orange colour, plenty of material, no burning on any steel plates. The actual drum for the E clutch is also burn mark free, which this drum can often have blue burn marks on it, so the E clutch & drum looks in good nick and hopefully no bushing failure.
Clutch Pack A, minor scorring on the steel plates, besides that the clutches are brand new. The thin metal plate at the end of the clutch pack is warped but I believe every pack has this characteristic, probably normal but if anyone knows better let me know.
Clutch Pack B, first steel plate had black residue from clutch on it, wiped off and no major burning. Slight blue tint in the cog of 1 steel plate, clutches look fine, plenty of material.
Clutch Pack C, very obvious burning on each steel plate, clutches look fine, plenty of material.
Clutch Pack D, basically brand new, nothing wrong with the steel plates or clutches.
In terms of drums and how they all fit together, they seem like they have no obvious play in the shafts. It looks like this gearbox was taken out of a 520d which had a very easy life and probably no more than 100-120k miles, but the breaker has no clue what car this came out of as it was a clearance offer when I picked it up.
I've attached photos, but I would like advice, if there's anything that I should just remove off the rebuild parts, then that can save me money. Personally I don't believe I need any clutch packs and might just replace that first E clutch for £8 instead of the full £175 if I don't need them.
I want to replace the bushings, because they do cause all the E clutch problems, but if I very obviously don't have them problems right now, should I even do it? I don't know the difficulty of replacing bushings but I do know theyre integral to oil pressure and not something you want to mess up.
Sonnax Zip Kit is basically a must, don't think theres any reason not to do it tbh.
I think putting a refurbed valve body is the smart decision, kinda like torque converter you just sort of do it.
The rebuild kit which is all them big rubber rings, is that necessary? Never really heard of them giving problem and truthfully I don't even know where any of them go.
Thank you for anyone reading this far, any advice would be greatly appreciated. Hopefully the photos I have provided serve useful, I'm unsure how to group them in order tho unfortunately, so just cross reference the images with my description to figure out which pack it is. C and E clutch are only ones somewhat notable anyways.
