UK Class 171/7 acceleration to 85mph - odd gear change

Southern Class 171/7
Manufacturer: Bombardier
Engine: MTU 6R 183TD13H (422 bhp)
Transmission - Voith T211rzze
Top speed - 100mph
Class 171s never get to hit top speed in service - the fastest section they travel along is from Oxted to East Croydon where the linespeed is 85mph from Woldingham to South Croydon. Leaving Oxted the stronger performing units will ease up once they’ve reached 60mph in the Oxted Tunnel. The gear change at 67mph almost always happens as the train is passing through the platforms at Woldingham.
171724 here, part of an 8 car formation, had an unusually drawn out gear change at the time of recording - it is initiated right on cue at 4:24 and takes about 16 seconds to settle into direct drive. Meanwhile the fans demonstrate a 3 second lag responding to the large changes in transmission speed!
1:19 - cooling fan on
3:30 - Oxted Tunnel - 60mph reached
3:46 - Linespeed to 85mph
3:57 - cooling fan off
4:24 - gear change initiated
4:30 - cooling fan on
4:40 - gear change complete
5:00 - cooling fan off
5:08 - 83mph reached
#TrainRideTuesdays
#TurbostarFamily

[@kevr1983]

Sounded like an epic transmission slip into direct drive.

[@MPDTransport]

Fabulous video

[@generalfilms9947]

These are the only Southern trains with comfortable seats there my favourite

[@InverhavonRailways]

Pretty sure what you can hear is the transmission switch from torque converter gearbox to direct drive and back. It happens at about 35-40 mph.

[@plasmauktransport1657]

Very good motor.. wonder how long these will stick around at Southern now

[@olskutsuikkeli]

Engine, because it’s a diesel train

[@PigletTube]

That acceleration is good.

[@RegiRaidillonVT]

I think I can just about hear the transmission whining too. Love that :) That gear change did not sound right

[@lgnatiusReilly]

Hear it on the outside

[@FM60260]

That at 4:23 I think could have been the driver starting reduce power after seeing a double yellow which almost immediately cleared to green so they applied full power again.

[@louis945]

No there is an engine transition/gear change when reaching 70mph causing the engine to power down slightly

[@FM60260]

@@louis945 The Sprinters & Pacers with T211r along with Desiros with T312bre that I have encountered have never done that so it doesn't make sense for a Turbostar to have to do it.

[@louis945]

@@FM60260 Well they do, search it up, Turbostars are made by bombardier, pacers and desiros aren’t

[@FM60260]

@@louis945 Bombardier don't make the transmissions

[@arianaashworth3091]

@@louis945 I have been on many Turbostars and they don't power down to shift. You only hear the rpm drop as it changes gear before slowly rising as it continues to accelerate, just the same as refurbished 14X Pacers, 15X Sprinters (with the exception of 151 & 154), Super Sprinters, 165, 166, 168, 170, 171, 175. It's typical Voith behaviour.

[@lawrencediangana]

Great Video :)

[@fenners1290]

Beleive these only have a three speed Voith Tr211 gearbox.

[@arianaashworth3091]

T211 is two speed, T312 is three speed