Can’t figure out a Gearbox problem

[MWField]

Can anyone help me please? My SV6 has an intermittent problem that’s driving me nuts.

Checked with a mechanic - no fault codes.

Started with the cruise control disconnecting and wouldn’t reengage. Wait a while and then it’s fine.

Now it’s developed to dropping down a gear or even 2 while driving steady on the motorway. Can be quite startling at 100k/h when it drops to 3rd and revs go to about 3,500. Feels like hitting the brakes. When it dropped down yesterday I went to manual and selected 5th which it showed on the dash but it didn’t change gear. I was shifting between 4th and 5th on the dash but no rpm change so I don’t think it was changing gear.

Also sometimes get the stability control off warning then the gear changes but not always.

Sometimes it happens once or twice other times up to 10 times. Can drive for an hour just fine other times starts happening pretty quickly. Can go for a few days no problems other times can happen all the time. But definitely the trend is getting worse.

Just a heads up, if it kicks back like that round a bend on the hyway (wet road), it's extremely likely to cause your life to flash before your eyes, even on a straight (wet road), your going to s**t yourself.

I wouldn't drive it but at the end of the day it's your call.

 

[carcollector]

If it's a 5L40 and it feels like it's kicking in and out of overdrive (which might also cancel the cruise control), it's a sign of terminal gearbox failure. If you catch it early enough, you might get away with a gearbox service and a new/recon torque converter. The torque converters crap themselves, filling the filters with metal filings and that drops the trans fluid pressure, so the trans fails.

 

[Crunchy Granola]

If it's a 5L40 and it feels like it's kicking in and out of overdrive (which might also cancel the cruise control), it's a sign of terminal gearbox failure. If you catch it early enough, you might get away with a gearbox service and a new/recon torque converter. The torque converters crap themselves, filling the filters with metal filings and that drops the trans fluid pressure, so the trans fails.

Ouch ! 5 grand for a rebuild?, I wonder if it would be cheaper to convert to a manual box?.

 

[Fu Manchu]

It’s more than $5k now.

 

[Fu Manchu]

Ouch ! 5 grand for a rebuild?, I wonder if it would be cheaper to convert to a manual box?.

I wish I did that in hind sight.

 

[J_D 2.0]

I wish I did that in hind sight.

That’s what I would have done had I decided to keep my old SV6. Instead I bought my manual SSV.

 

[lout]

i dont believe an internal transmission fault would disengage cruise without setting a code
so leaves me a with 2 faults
pedal position sensor for dropping down gears .
and possibly brake sensor or globes ,intermittent to disenage cruise
or most likely wiring under dash to accelerator pedal sensor and brake pedal sensor to cause both conditions