Just wondering if ayybody has much experience or knowledge about these modifications that are done by Ashcroft as quoted below, who does these mods in Aus (Pref Sydney) and what type of $ it is all worth to have done. The Disco get's serviced etc by Davis Performance Landy's though I have not chatted to them about it yet.
http://www.ashcroft-transmissions.co.uk/part_18.html
Heavy Duty ZF autoboxes
We are able to supply the ZF4HP22 with optional strength upgrades depending what you are doing with the vehicle, what gearing, what engine Etc.
Stage 1 upgrade
We can build the 4HP22 but fit the centre section of the box with the bigger 4HP24 internals which upgrades one of the weak links being the C1/C2 one way clutch, the 24 one is much stronger, Photo here. Just the centre internals are changed so the box stays the same externally. This upgrade is an additional £ 250 on top of the normal rebuilt exchange price of £ 595 or £ 645, depending if the box is hydraulic or electronic.
Stage 2 upgrade
The box can be built with both the 4HP24 internals as above but also the 24 front end as well giving you the added strength of having the larger 24 "A" clutch, also a weak point with larger engines.Photo hereThere are 2 fitting implications of doing this, the unit is 15mm longer and the oil cooler nipples are M18 x 1.5 thread, on the early 22"s these threads are M16 X 1.5, the later 22"s like the TD5"s are already M18. This upgrade is an additional £ 500 on top of the normal rebuilt exchange price of £ 595 or £ 645, depending if the box is hydraulic or electronic.
Torque Converter Upgrades
The ZF auto as used in the LandRover vehicles uses three different diameters of torque converter. Small. Medium and Large.Photo here
"Small" is used on the 300 Tdi, P38 diesel and the TD5 "Medium" is used on the 3.9, 4.0 and the later 4.6 P38 "Large" is used on the early 4.6 P38"s
The converter has a lock up clutch inside and the smaller one struggles to cope with a stock engine, never mind a tuned one.
When the "stage 2" ZF is being used with a V8 or 2.8 TGV you have the option of using the larger diameter 4.6 torque converter at no additional cost but on a V8 you will also need the 4.6 boss and flexplate assy to match the bigger converter. When using on the 2.8 be sure to order the conversion kit to fit the bigger 4.6 converter. This bigger converter is recommended on the big V8"s and the 2.8 as it keeps the revs and heat down.
If you have a tuned TD5 engine, in addition to the stage 1 or 2 options mentioned above we are now able to replace the "Small" diameter torque converter for the "Medium" diameter one. This gives you the benefit of the larger lock up clutch and the lower stall speed V8 torque converter which will take up drive earlier. This option is an additional £ 250.
TD5 ZF upgrades
If you are converting your TD5 Defender to auto you have a few options, I though it may be useful to give some guidance based on our experience.
Stock 90/110, fine with a stock 4HP22 Medium Tuned 90, stock ZF, uprated converter Medium Tuned 110, stage 1 ZF, uprated converter Fully Tuned 90, stage 1 ZF, uprated converter Fully Tuned 110, stage 2 ZF, uprated converter Tuned Challenge 90, stage 2 ZF, uprated converter
