17 replies to this topic

[D-Train]

I'm almost ready to start my car. Know I'm worried the Trimatic won't shift correctly with the supercharger giving no vacuum to the modulator. I've been told there are adjustable ones, but I can't find it.
Should I just give it a go and see what happens, or go full manualised trimatic?
Help!!!!

[76lxhatch]

This one is stupid expensive to ship, but gives you a part number (also note TH180 and 3L30 which are alternate GM codes for the Trimatic, might help in your search):
https://www.ebay.com...M-/281926329044

I would have thought that most people would only sell the adjustable version these days, they may not state so would pay to ask.

[D-Train]

For that shipping price, I'd expect it to be at my door a minute after ordering.

[UCgazman]

Ask the seller if he can do a better price on shipping - the Yanks use ebays 'global shipping program' which is specifically designed to rape the bank accounts of all non-US buyers. If they are a high volume seller they know they can get a better price at the post office. Some will, some wont, but I always ask...

[Torana 202]

I'm almost ready to start my car. Know I'm worried the Trimatic won't shift correctly with the supercharger giving no vacuum to the modulator. I've been told there are adjustable ones, but I can't find it.
Should I just give it a go and see what happens, or go full manualised trimatic?
Help!!!!

 

What sort of blower, carb, injection set up do you have?  

 

What vacuum figures are you seeing on the gauge off boost?

[Oversteer]

Modulator won't work properly with boost, adjustable or not, you either need to go to a cable operated(works of throttle position) or full manual the auto.

 

Don't know about the trumatic but the TH350 and 400 have aftermarket cable operated modulators or if you can find it the TH400 was used in alison trucks with detroit diesel and a cable operated modulator.

 

I had a SBC TH400 with a turbo in a landcruiser.....nothing can be done to make vacuum modulator do its thing right, cable operated worked pretty well, imo full manual auto's suck balls for street driven cars so i didn't want full mnual....which was the response i got from any transmission and or performance shop etc.

[mick_in_oz]

Full manual Tri, AWSOME!

 

Full manual Tri on the street, still AWSOME!

 

TH350-400, they still have a vacuum modulator, but a cable operated Kickdown.

 

Early Tri has a cable (pushrod?) kickdown, but I've never seen one in the flesh.

 

Do you need to even bother with connecting a Vac line to the modulator, its only there to bleed off line pressure during situations of light throttle to soften gear changes, with no Vac connected it should only firm up the changes.

 

Full manual Tri on the street with no vacuum connected to the modulator, gets a lil chirpy with the tyres, but still AWSOME! 

[D-Train]

That sounds good Mick. I'm not very clued on auto gearboxes. I thought it was needed to decide when it needed to change up.
It does have a cable kickdown, but I had some help on another post and that is now sorted. I'd be happy to. Leave it off if it's just going to give me more bang for my buck(gear change). That doesn't bother me in the least.
I do want to fully manualise it, but I'm too close to finishing to start pulling it apart again. As any builder knows, one small job leads to another and another and a full resto by the end.
I might just see what happens when I take it for a test run and go from there. How does that sound?

[D-Train]

Torana 202'
I got a virgin black efi 202, then had the whole block redone. 30 thou bore, zero deck. 15cc dish pistons. 12 port yella terra alloy 56cc head. Running 8.1 static cr.
Running an m90 with a w2a I/c into the standard vk efi throttle body and runners. Wolf 3D ecu will be doing my nerdy bits and I have an lm2 to get it within a decent range before I can be bothered taking it to a dyno.
Not running yet. Everything but the wiring to go. Bloody rats nest these things are. I'll keep you all informed.

[Torana 202]

Sounds good, where do you intend on hooking up the modulator line (before or after the blower)?

 

Trimatic modulators don't like boost and will eventually leak, a bleed or 3 port solenoid can be used to ensure the modulator never sees boost.

 

Manual valve body conversions are usually done on series 2 or later boxes.

[76lxhatch]

The boost thing never even occurred to me, that could be an issue but sounds like Torana 202 has some ideas on getting around this. Possibly why GM changed to cable operation.

You can't just disconnect the modulator though (unless going full manual), the trans won't work properly. This is what controls the shift points both up and down - the trans will generally function without but shifting will be horrible and you run the risk of damage because its not load-referenced.

[Dr Terry]

I ran a turbocharged 186 with a TriMatic for years, no problems.

 

If you connect the modulator line to a point before the blower, it will never see boost & the trans will shift properly. You can't run without a modulator.

 

Dr Terry

[EunUCh]

The vac mod needs vac to operate , it "talks" to the governor to determine shift points , from memory when I had vac mod with no vac it would nor change out of 1st but did not push the issue to see if it would upshift , probably the only way you will get a vac signal with a blower is to shift the throttle plate to the suck side of the blower and fit a vac take off behind the plate and you should be still able to tune it no problems, although you will need some sort of boost reference to the ecu to pull a bit of timing out and trim the fuel curve ?

[D-Train]

Currently I'm using I micro switch and a solenoid for the kickdown as there's no room.
So if I connect the modulator to the intake side of the blower I should get vacuum during acceleration as it's dragging air ? There is a nipple I can use on the intake side of the blower.
Another idea I just had was run something lie a Venturi but this could cause too much vacuum, could that be a problem?

Cheers for all these ideas, there Greta. Keep me coming. I wish I did a build thread from the start, could of saved me countless hours and redos.

[Torana 202]

You don't want any sort of vacuum applied to the modulator while you're on boost, vacuum on the modulator while accelerating will lower line pressure and lead to possible slippage burning up frictions. 

 

The standard Trimatic is also designed to cut back on line pressure as road speed increases for fuel economy, this can also be a cause slippage with engines that make decent power.

 

With blow thru turbo motors I run the modulator line to the vacuum tree on the inlet manifold through a 3 port solenoid controlled by a vacuum switch, when zero vacuum is sensed the solenoid vents the vacuum modulator to the atmosphere. A one way valve and bleed is another way to do it.

[D-Train]

Thanks torana 202. Could you explain the three port solenoid to me as I'm not so,bright when it comes to trannies.

[Indy Orange]

I've never been able to work out tranny's.

[Torana 202]

Thanks torana 202. Could you explain the three port solenoid to me as I'm not so,bright when it comes to trannies.

 

Use an ADR27a  vacuum advance control solenoid off a late model Torana, HX-HZ Holden. Connect the rear port of the solenoid to the vacuum tree where the modulator steel line normally gets connected to (note the factory restrictor is less than 1mm) , connect the solenoid side port to the steel modulator line that goes to the modulator, leave the front solenoid port open.

 

You will need a vacuum switch to control the solenoid set to activate at zero vac. this will vent the modulator to the atmosphere whenever on boost, the modulator will never see boost and there will be no leakage. doing it this way.

 

The vacuum source can also be between the throttle body (using a restrictor like the one built into the vacuum tree) & blower but the vacuum switch must be connected after the blower on the inlet manifold to work correctly.