Auto Gearbox Issue - ECU or Mechanical??

[zakmuh]

Hey Guys,

Hope you all are well. Today I'm here seeking some knwoledge to understand and clarify wheather the common auto gearbox problems that many cars suffer these days are caused by faulty ECU and not by worn/broken parts inside the gearbox.

The followings are some DIY jobs I did in the past to solve the gearbox issues, which were initally advised by garages and dealers that it was mechanical issue and need to replace the complete gearbox (costing £1200 to £2500). Some advised to refurbish the unit taking to greabox engineers:

. 2001 MB A170 with no gear shifting at all and went to 'F' mode - faulty ECU refurbished (£180) by ECUTesting in Derby.
. 2002 BMW 735i with juddering and went to 'P' mode - Replaced a cracked plastic adapter (£35) inside the gearbox
. 2004 Mini Cooper with stuck in 1st gear - Replaced the gearbox oil with Ultra-High viscosity oil (bought on Ebay from USA)

So, can I say that almost in all cases, mechanical parts are robust and they hardly go wrong in an auto gearbox (unless you run with no or little oil)?

Any thought and advice would be highly appricated.

Cheers
NB: There is a 2005 Volvo XC90 T6 for sale with gearbox issue - stuck in 1st gear. I was just wondering if I should buy this as a project car.

Edited by zakmuh on Wednesday 4th May 09:07

[PositronicRay]

zakmuh said:

. 2001 MB A170 with no gear shifting at all and went to 'F' mode - faulty ECU refurbished (£180) by ECUTesting in Derby.
. 2002 BMW 735i with juddering and went to 'P' mode - Replaced a cracked plastic adapter (£35) inside the gearbox
. 2004 Mini Cooper with stuck in 1st geear - Replaced the gearbox oil with Ultra-High viscosity oil (bought on Ebay from USA)

So, can I say that almost in all cases, mechanical parts are robust and they hardly go wrong in an auto gearbox (unless you run with no or little oil)?

Any thought and advice would be highly appricated.

Cheers
NB: There is a 2005 Volvo XC90 for sale with gearbox issue - stuck in 1st gear. I was just wonderinf if I should buy this as a project car.

Well done diagnosing and fixing the above. However I would suggest that putting extra thick gloop in the Mini wasn't a fix, more of a bodge for a worn box. The kind of thing done to prolong the life of a shed, or an unscrupulous seller might do.

[zakmuh]

PositronicRay said:

Well done diagnosing and fixing the above. However I would suggest that putting extra thick gloop in the Mini wasn't a fix, more of a bodge for a worn box. The kind of thing done to prolong the life of a shed, or an unscrupulous seller might do.

Thanks mate.

Well, Cooper didnt throw up any issues eversince though. I have the habbit of chaning gearbox oil every six months. I know it isnt necessary but I just do it, for a peace of mind

[PositronicRay]

zakmuh said:

PositronicRay said:

Well done diagnosing and fixing the above. However I would suggest that putting extra thick gloop in the Mini wasn't a fix, more of a bodge for a worn box. The kind of thing done to prolong the life of a shed, or an unscrupulous seller might do.

Thanks mate.

Well, Cooper didnt throw up any issues eversince though. I have the habbit of chaning gearbox oil every six months. I know it isnt necessary but I just do it, for a peace of mind

Just an opinion. If I was offered a car and knew that gearbox problems were fixed with some gloop imported from America, would I be likely to buy it? It wasn't Lucas was it?

[zakmuh]

PositronicRay said:

Just an opinion. If I was offered a car and knew that gearbox problems were fixed with some gloop imported from America, would I be likely to buy it? It wasn't Lucas was it?

Sorry I didn't get you Ray

[CraigJ]

I'm self employed and work on a specific type of auto box on a daily basis doing diagnostics and repair work. For me I would say around 75-80% of the time the issue is repairable. Mostly electrical or failed mechanical parts that can be replaced/repaired to keep the transmission on the road. These transmissions have covered at least 400,000km before they even come to me.

Today I got back on the road two more, one of which had covered 960,000km

I cant speak for all auto boxes but for me I find that the majority are repairable.

[zakmuh]

CraigJ said:

I cant speak for all auto boxes but for me I find that the majority are repairable.

Craig, thanks for your response.

I completely agree with you. I haven't heard anyone like you (sound knowledge of gearbox) telling me anything about replacing mechanical parts like gear wheels etc. It'd be like leaky capacitors, burnt resistors in the ECU or some plastic lever/cap. Most of the times it's do with mechatronics parts.

Cheers

Edited by zakmuh on Tuesday 10th May 09:10

[zakmuh]

Hey guys!

A quick update...I just found out from a Volvo XC90 T6 user that his greabcox used to get stuck on the 1st gear. He had to keep restarting the car each time to get him home. Then he sorted it out by updating the TCU software through the dealer. It's been a couple of months now and the problem never turned up again.

And also, he converted AWD to 2WD (only front wheels working) by removing the drive shaft connecting the rear transfer box and unplugging some fuse. This gives him a very good mileage, apparently?

Cheers

[PositronicRay]

zakmuh said:

Hey guys!



And also, he converted AWD to 2WD (only front wheels working) by removing the drive shaft connecting the rear transfer box and unplugging some fuse. This gives him a very good mileage, apparently?

Cheers

I would think it's a failed Haldex clutch.

[zakmuh]

PositronicRay said:

I would think it's a failed Haldex clutch.

He didnt mention anything that the car had any issues with the transfer box. He simply disconnected it as he didnt want all 4 wheels to work + to aviod any issues in the future.