Advice on car please!

[J_D 2.0]

I like The Car Care Nut and enjoy his videos and his advice but I’m still sceptical about the notion that one shouldn’t flush an older auto as the floating clutch particles are providing grip that the clutches need to grab the gears (while not blocking the fine oil passages and solenoids within the box itself?).

If such was true, given all the businesses selling snake oil remedies within our parts stores, you’d expect to find a transmission fluid additive containing finely ground clutch material for added grip I’ve seen transmission additives that claim to reduce slip. I suspect such is achieved by softening the seals which helps those one way ball values and solenoids work better and this provide the designed pressure to the clutches (none claim any form of clutch material is contained within specifically to aid clutch grip)

In my view a full flush is the way forward and if an auto then slips with the correct fluid level within, because all the clutch material has worn out and was dumped with the old fluid, the trans is already stuffed and you should be considering a rebuild

Well the recommendation is mostly because the transmission may be relying on that extra friction to not slip if it’s old and you don’t really want to find out your up for an immediate rebuild 5 seconds after you take it in for a “harmless flush”.

Sure the transmission is almost certainly on the out anyway but the flush forces it to immediately show its hand and for you to immediately go all in on a transmission rebuild you probably weren’t planning on!

The far safer option is to replace a portion of the fluid through the pan drop and if/when you start getting transmission slip you might have a few months before it craps out entirely to get the money together and book in the trans rebuild, or replace the car entirely.

 

[blackvxss]

And with the full flush process, how do you know if the mechanic has done it properly?

its on the bill with the blinker fluid top up.

 

[figjam]

I will make an exemption to the CVT rule as Toyota's are pretty good with their CVT's, and much smoother than let's say a Jatco box...

Hired a Corolla in Uluru in 2014, drove it to Kings Canyon and back, didn't know it was CVT until I looked at the specs when we got home.
Not that there are many gear changes required on that peak hour, congested, stop / go stretch of road.

 

[Geoff6666]

And with the full flush process, how do you know if the mechanic has done it properly?

Because he said so . . . .

 

[Skylarking]

I’m just being my usual pedantic self, so I think it’s important to distinguish between a ‘pan drop’ (my term) fluid change and a ‘full transmission flush’ fluid change. GM (and Holden) use to recommend a full transmission flush which involved a special machine to change over the fluid through the whole system (I think there is a section in the VF service manual that shows the process?). Apparently this caused more issues than it solved (failed valve bodies???), so now they just recommend the ‘pan drop’ method, and not to do the full flush. I can only speculate that the full flush might have been loosening up some build that might have later gotten stuck in the smaller passages within the transmission?

This may simply be an unstated acknowledgement that the transmission service is too long between drinks and thus gummy’s up… It can also be an unstated acknowledgment that their flush machine ain’t a great design in that it may spread crap from one cars transmission to another because their gold standard service techs don’t clean the machine well enough between uses?

Guess the cynic in me, built up over years of experience, says GM/H won‘t have my back post warranty… Heck half the time they try and stab you in the back during warranty…

My view that it’s of benefit to perform a full flush and filter change at 1/2 GM’s service interval (or shorter) and that’s what may be what’s needed for longer life in GM’s almost sealed for life transmissions.

If GM were serious about transmission life, there would have been a quality full flow spin on filter between the box and the mandatory factory fitted cooler (while a simple screen filter within the sump would have done the job of catching the LS3 rocker’s needle bearings if they made their way into the sump)…

(if I kept a copy of a SAE technical journal article , id post it… that article discussed the development and proof of an algorithm that defines the fluid temperatures at the clutch faces with varying amounts of (comfort) slip. If you saw those temps, you’d want to change all your fluid more regularly…the temps are insane)

 

[Skylarking]

And with the full flush process, how do you know if the mechanic has done it properly?

How do you know a mechanic has done anything properly?

 

[Skylarking]

Well the recommendation is mostly because the transmission may be relying on that extra friction to not slip if it’s old and you don’t really want to find out your up for an immediate rebuild 5 seconds after you take it in for a “harmless flush”.

I‘d agree that if you have neglected your transmission you’d may have problems that can be amplified a little by doing a flush or even a pan change. However, in those instances, I’d expect you were already on borrowed time and the fluid flush was a Hail Mary attempt at avoiding a trans rebuild…

Best avoid such pain and not wait the full 150,000 kms before doing a trans service. Better to flush at 75,000kms (severe schedule) unless one tows in which case I’d even bring that forward to 50,000kms or less…

 

[J_D 2.0]

If GM were serious about transmission life, there would have been a quality full flow spin on filter between the box and the mandatory factory fitted cooler

Subaru did this on the early Tribecas. The spin on filter makes SFA difference to fluid filtration as the majority of the fluid bypasses the spin on filter anyway as you risk fluid starvation by forcing it all through the spin on filter. They deleted it on later models of the Tribeca.

 

[RevNev]

My view that it’s of benefit to perform a full flush and filter change at 1/2 GM’s service interval (or shorter) and that’s what may be what’s needed for longer life in GM’s almost sealed for life transmissions.

Yes, I agree! I've thought about doing my SV6 trans although the car has only 28600km's, March '16 build, the trans fluid has been in there for nearly 7.5 years and too long for my liking not being a fan of the "fill for life" ideologies. I've dropped the trans pan off many cars over the years with some seriously dirty looking oil in there!

 

[Skylarking]

Subaru did this on the early Tribecas. The spin on filter makes SFA difference to fluid filtration as the majority of the fluid bypasses the spin on filter anyway as you risk fluid starvation by forcing it all through the spin on filter. They deleted it on later models of the Tribeca.

It’s why I said full flow filter…. Bypass filtration sucks…

It’s not rocket science to design a full flow filter with a pressure sensor on each side of the filter reading the pressure differential. TCU can then read the pressure differential and in over a set level flag a “change transmission filter soon” message, if ignored and pressure differential increases, flag DTC, turn on Check engine lamp and go into limp mode.

Just cost another pressure sender and some wires, maybe a comparator… but manufacturers are cheap beasts and prefer designed obsolescence