Folks, does anyone know if the 6 speed box fitted on the later models is any stronger than the 5 speeder ? The 5 speed box seems to need replacing anytime between 60 and 120k. Does the 6 speeder last any better ?
In a past life I was transmission engineer @ Aston Martin
(not as great as it sounds) working
on DB7 and Vantage. We did many tests on the manual transmissions
used which were Getrag 280/290 Model on the original 3.2
(Later V12 used Tremec BWT T56 6 speed due to
power and torque output )
I believe the Getrag 280/290 is the same type of transmission as used on E34 M5
The 5 speed has small probelms like fragile idler shims and can whine a little
on the coast side of the gear teeth as wear increases and the the crest
of the intermeshing gear contacts
the root of of the corresponding gear. (trieing to keep it simple
& not sound like a boring nerd!)
The biggest killer of the transmission that I have seen from testing is abuse
from cold & insufficient oil maintenance.
Next down the line is thermal issues running for long periods
above 230kph where temps exceed 150 degrees Celsius thereby
causing premature breakdown of seals and hardening on gear contact faces.
My humble advice is that these transmissions can be long lived
to 300,000 kilometers plus with very little maintenance and regular
oil changes on trans & diff oil to remove metal particulate debris
In addition these regular changes maintain the
anti-shear additives within transmission and differential. 5 speed or 6 speed
should be similar.
The main difference I feel is the shift seems
notchier on the 6 speed than on the 5speed. but
purely a subjective view.
farrell, thanks for the great info - not drivel at all !
I'm intrigued though. Having looked at countless M5s at around 120-140000 miles, almost without fail they had there gearboxes changed sometime between 60 and 10000miles. All had impeccable service histories and presumably therefore had there fluids changed at the recommended intervals. M5s are probably going to have a hard life and the recommended fluid change intervals should take this into account. Are we saying then, based on experience, that the recommended intervals are too long ? If so, how often would you recommend the gearbox and diff fluids be changed ?
Hi Nick
In a nut shell I am saying that abuse / wear of engines and transmissions is at its worst within the first 5 to 10 minutes of start up
Back in the 1960s-70s when engine materials and surface treatment of load bearing surfaces was not as efficient a science as it is today, many high performance vehicle manufacturers like Jaguar and Ferrari recommended intitial run in periods around 12-1500 miles followed by a fluid change of engine, transmission and differential if applicable. These cars put greater thermal and torque loads on the drivetrain.
Manufacturers skip this today to save money.
If you drain the trans oil on most so called sealed for life transmissions these days after only 50,000 miles I believe most would be staggered at the amount of metal debris sloshing around between all those moving parts. This can only accelerate wear & decrease the oils efficiency in terms of lubrication & dissipation of heat.
Manufacturers like Ford conduct durability testing / highly acclerated life testing (HALT) to ensure a vehicle can survive on average 10 years /150,000 miles in the hands of the 95th percentile customer without major failure. This takes into account the broad spectrum of driving styles. The manufacturer knows that its transmissions have debris in them but try to make them as cheap to manufacture and as quick to service as possible.
As long as they do not suffer mass premature failure then they have achieved their their goal.
With the type of cars we own, most of us are not the original owners of these £50,000 cars. The profile owner was not an enthusiast (as most of us are) but a corporate executive who got in the company car and thrashed the nads off it for three years and probably was not to timely with the services either.
Years / miles down the road we pay the price for all the early abuse dished out by former owners. I believe that this may account for early failure of transmissions which usually have had a really hard time.
Your observation on the mileage failure is indicative of hard use but is approaching that magic 150k distance. I believe that there will be 180-200k cars out there that still have their original transmissions though I know of only one personally!!
Sorry to be so long winded but thought background test info
would give you an idea of why these parts should not fail
so early. I certainly do not doubt your valid observations but feel
some of the points raised may allow us to understand the reason
My car is @ 124,000 with original box and I am changing oil every 12k. Its quiet & does not whine (unlike my other half !) I may be tempting fate but I think it will exceed 150k easily.
Regards Farrell
(Being nagged mercilessly somewhere in Essex !)
farrell, there is no need to ever apologies for this sort of email, which is full of useful knowledge that I and many others will want to read. Thanks for taking the time to post
Gearbox strength
Linear Mode
