Drag force is proportional to the square of the speed. Drag power is proportional to the cube of the speed. 100bhp for 100mph would require 800bhp for 200mph. Phil

Taking your average family runabout as an example, the Bugatti Veyron has a drag coefficient of 0.36 and a frontal area of 2.07m^2 (according to Wikipedia). At 250mph (i.e. 111.76m/s) the aerodynamic drag will therefore be 0.5*1.23*0.36*2.07*111.76^2 - assuming an air density of 1.23kg/m^3...

Worse than that, drag is a force so the power requirement has to be multiplied by the speed again, so the power requirement to shove a vehicle through the air is proportional to the cube of the speed. Phil

The NV225 transfer box ECU isn’t coded to the vehicle so, yes, it’s just plug-n-play. There were several software updates over the years so its part number changed from : IGG 000100 to IGG 500040 to NNW 500440 to IGG 500100 to IGG 500101, so one of the later ones would be better. A new IGG...

I admire your optimism but I’m afraid it’s much more likely to be your transmission playing up than the transfer box. Next time you lose drive put the gear selector into Park with the engine still running and the handbrake off and see if the park lock holds the vehicle. If the vehicle will roll...

John Mackie’s transmission workshop in Tollcross is a highly respected ZF specialist. Mackie Automatic Transmissions 95 Causewayside Street Glasgow G32 8LT Phil

The bushes aren’t expensive (a full set containing all 14 costs around £60) and the stator is the first thing to come out of the transmission, along with the oil pump, when it is disassembled. It therefore isn’t necessary to rebuild the whole transmission to replace the stator bush. The...

Could be that the rear stator bush has worn (common fault with the 6HP26) and it’s allowing the hydraulic pressure for the E-clutch to escape. The E-clutch is used in 4th, 5th & 6th gears so the mechatronic defaults to 3rd gear if it senses the clutch slipping. Phil

If you’re resetting the adaptions because new software is being flashed then just follow the appropriate adaption drive cycle afterwards until the new solenoid settings are learned. Don’t change the fluid at the same time, change it at a later date. The idea of the long-term adaptions is to...

"...I'm in the predictable situation of a totalled TDV8 6 speed gearbox" Nothing predictable about that – the ZF 6HP26 transmission has an enviable reputation for reliability. Having said that, these are the known issues that occasionally affect this transmission : 1. Transmission won’t shift...

When mine went I just replaced the 20cm or so of the two melted wires and the connector, plus a new thermostat assembly. Phil Edit : assuming that you meant the thermostat heater rather than the coolant sensor

Yep, the 3.6 TDV8 was introduced for 2007 model year Phil

Hi Andy, If you’d like to PM me your email address I can get back to you with a quote (assuming yours is the ZF 5HP24 transmission?). I should point out though that I only work on transmissions, and not vehicles, so you would have to make your own arrangements for having the transmission...

The fix may be as simple as lubricating the gearshift cable clamp bolt which sometimes becomes so corroded that it will no longer articulate in the hole in the selector lever (necessary because the cable moves linearly and the lever through an arc). This causes the gear lever position and the...

The transfer box bearings are certainly a possibility: http://www.fullfatrr.com/forum/topic12404.html Phil

Okay Pete, I look forward to hearing from you. With the friction plates, you can buy a complete aftermarket set, like these Exedy ones at £77 : https://www.ebay.co.uk/itm/Audi-BMW-5HP24-Automatic-Gearbox-Friction-Kit-Exedy-/192110410573?hash=item2cbaac3b4d By the way, the A & C plates are...

The D brake for the Range Rover variant of the 5HP24 has four friction plates. There are quite a large number of heat spots on the ones from Pete’s transmission and that isn’t uncommon. This brake is the most susceptible to overheating in the 5HP24 and on higher torque variants i.e. the BMW E53...

The B & C clutches next. Pete’s B clutch pack has a single heat spot on the inner half of the steel plate facings, which is very common. The friction plates show heat glazing in the area corresponding with this. The C clutch pack is in perfect condition. The C clutch is only...

Pete and I decided that it might be best if he left the six clutch assemblies with me for dismantling, as I have the special tools to compress the springs using a mandrel press. Pete will, of course, be rebuilding the transmission himself. I usually just work through each of the clutches in...

Pete, I’m pleased to say that none of the remaining screws put up much of a fight. Phil