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Turbo 400 not kicking up to 3rd gear when hot...

Hey there, I have a HZ van with a 308 with a Turbo 400 tranny. I have been having problems with the tranny after a longer (or hotter day) drive (say over an hour to 2 hours+). After driving for that period of time in third gear, after you have come to a stop and then drive off again, it gets stuck in 2nd gear and you have to ease off the accelerator, then put your foot down then it eventually kicks back up to 3rd. But not all of the time.

Sometimes after that it will be in 3rd (3000rpm) then the speed stays the same but the revs go up to 3000-3500rpm and it is revving hard. Other times it gets stuck in 2nd at like 2750-3000rpm and just wont shift into third at all. A bit of a problem if you have to do 100km as you dont wanna blow up the tranny or motor.

Sometimes on occassions I see a waft of smoke come from the back. i just thought it might be an oil leak from the rear main hitting the exhaust or something and prob due to the fact that the engine and tranny is running hotter as it is stuck in 2nd gear.

I thought that these trannys were pretty much bulletproof. 1st to 2nd gear is no probs, only 2nd to 3rd gear when it has been a longer trip and/or a hotter day (Like when its 40 degrees). So a trip to Sydney is out of the question.

Was wondering if anyone knows what the problem is, and if it can be fixed. and if so, if there is a good, honest, reliable and comprehensive reapairer who is not gonna rip me off and be full of lies. Maybe it is a switch or something that needs replacing?

Would a reco or a rebuild off the current tranny be better?


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Hi not being a smart ass but

Hi not being a smart ass but have you checked the oil in the tranny also it will do this if it is over full. the other thing is the vacum lines make sure they are in properly and the rubber tube on each end has no splits or to long some times it will do what your problem is. other than that it is probably the bans in the box need ajusting or replaced.

Yeah the tranny oil is at

Yeah the tranny oil is at correct level. It was serviced not too long ago.

troublesome T400

I've seen pretty much the same thing happen commonly with Trimatics.
The problem is usually a vacuum leak or a blockage on the modulator line.
A T400 has a similar set up and would probably have the same problem. The T400 modulator line runs from the vacuum tree on the rear of the intake manifold down to the modulator on the passenger side of the transmission.

Firstly check and make sure there are no leaks, the small rubber joiners on each end commonly perish and leak. If all checks out, with the engine running, remove the hose from the tree on the engine and make sure you have a good vacuum signal there as it is common for the small orifice to carbon up.

If these things are O.K. you may need to see a trans guy but I'd check these things first.


My Shed

T400 fault

David is on the money here !

Vac leaks from the Manifold to Vac Modulator is most likely the problem! Been there & seen it before :(

A Blocked filter could cause a "Similar" Problem?

Do what David advises first & If that doesn't work drop the Auto's Sump & replace the Filter.

Try all that prior to paying an Tranny Service centre!

Failed Modulator

"Sometimes on occassions I see a waft of smoke come from the back."

The Modulator diaphragm has a pin hole in it allowing ATF Oil to be drawn into the Inlet Manifold. Gives pharmaceutical smell in the cabin.

This is causing vacuum to be lost as Hq308belmont is saying.

You'll find the fluid level is down too.

You need a new Modulator as least (easy to screw off and on). Fluid will run out so measure this and top up the box with new fluid to the same quantity.


Holdenpaedia, they're the brakes Mate.

Modulator Image

The image (item 2) shows the Modulator on a Trimatic. The T400 part will look similar.



Holdenpaedia, they're the brakes Mate.

Modulator Image

I have added a TH400 pic showing the modulator clearly. See link below.


My EH Holden Shed

 Email Me

Postcode NSW 2560


Many Thanks


Holdenpaedia, they're the brakes Mate.


Well spotted T , I missed the line about the smoke coming from the back.

The T400 modulator attaches a little different to the Trimatic one, instead of screwing in it pushes in and has a little bolt on tab to hold it in place, similar to a Trimac speedo cable.

BTW, I screwed up on the location of the modulator it's actually on the drivers side of the box.


My Shed


Hi Dave,

If you could snapshot a photo and post it up I'll add it to the TH400 H Page and credit your name to it.


Holdenpaedia, they're the brakes Mate.


I'll try and get a couple of pics over the weekend.


My Shed

So a new modulator? Where

So a new modulator? Where would a good place to pick one up? Thanks

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