[The Scifi Guy]

I just made an awesome discovery! Adjustable TH180 auto tranny vacuum modulators! I had heard rumors about such a thing existing, but in 40 years of automatic Opeling and modulator buying I have never seen one. And, on top of that, there seem to be several types with different color stripes on them. If you have an auto tranny Opel with a Combo cam, you'll notice that your tranny shifts horribly at the wrong times because Combo cams drop your vacuum in the manifold a LOT. You might want one of these. Here's why I want one:

I had a 45DCOE single side draft on my 2.4 engine and the engine and tranny performed and shifted perfectly. REALLY perfectly. The engine stared and ran like an FI car and the tranny shifted perfectly and almost imperceptably and at the right time. I then installed a 45mm twin throttle body with fuel injectors and FI and now it won't shift at all unless I take my foot off the gas. Same size carb/TB, but totally different tranny shifting. Now, the 45DCOE carb had 38mm venturis restricting the air flow, but the throttle body doesn't have venturis, so all 45mm worth of air can come in with no restriction.

I put vacuum gauges in all my cars. They let me monitor if I have a vacuum leak forming and I get big fun watching the needle swing when I step on the gas and they help you manage your fuel economy a bit. Under normal, casual, acceleration your auto tranny should upshift at about 2700 rpm. If you floor it, it will shift later in the 3000's. If you really floor it and keep the pedal to the floor, it will shift in the 4000's. Under very light acceleration my tranny isn't shifting well up into the 3000's and I discovered that I have to take my foot off the gas for a secondor two to get it to shift. Downshifting occurs normally. So I started watching my vacuum gauge, with my new FI and TB's, and under very light acceleration I have basically zero vacuum and as I get up into the 3000+ rpm range and it's still not shifting and I ease off on the pedal a bit, when the vacuum rises to about 5Hg the tranny finally shifts. When idling or cruising at a steady speed down the road, vacuum is usually at between 10Hg-15Hg's, maybe as high as 20Hg's, this is the perfect, normal, vacuum for ANY car when cruising at a steady speed on a flat road. I never monitored the vacuum during shifting when I had the carb, so I have no idea what it was.

So, what does this all tell me?

I have a very low vacuum situation during casual acceleration that is causing my tranny not to shift and if I raise the vacuum just a little bit by easing back on the gas pedal just a little bit and increasing the vacuum, it does shift.

So, what can I do about it?

I found adjustable TH180 modulators! You can find adjustable TH350 modulators, but adjustable TH180 ones are hard to find. Why else would they be adjustable if not for the purpose of adjusting them to be more or less sensitive to vacuum?

Now, I have found several types on Ebay with part numbers of 5182 and 5183 and others identified as having blue or purple stripes on the outside. Only one of the adjustable types actually listed the adjustment range as "66-75Kpa" part number "JVM-5182". I have no idea how many different types there are, there might just be the two blue and purple stripe ones or maybe others. The stripes may mean different vacuum ranges. I don't know which type is best for my needs, I'm waiting for a seller to tell me which is best for my very low vacuum situation. I will update this thread when I find out more.

Edit: I have now found SIX types of TH180 vacuum modulators, with 3 different color stripes and each of those in either one stripe or 2 stripe variants, and I have found contradicting ads saying whether they are adjustable or not. Holy Cow, what a can of worms!

If any of you excellent Internet sleuths can find the answer, many Opelers could benefit from this knowledge. Your help greatly appreciated!

Here is a pic of the "normal", non-adjustable, TH180 vacuum modulator I just took out of my car:

Here is a pic of a TH350 adjustable modulator. It is not compatible, it does not screw in:

This is a pic of a blue stripe, adjustable, TH180 one with a screw adjuster in the vacuum hose outlet:

This one appears to have a green stripe/lettering:

This one has a purple stripe

Oh boy, I just found other listings that contradict previous ones. It appears that some modulators have 2 stripes and others only have one. Some say that one stripe ones are adjustable and some say they aren't.:

One blue stripe listed as non-adjustable:

Two blue stripes, adjustable

Two green stripes, listed as non-adjustable

 

[hrcollinsjr]

I found a reference!

Harold

P.S. Actual BWD part number.

 

[Young Gt Lover]

If you get more info on this I might buy on for my 69 gt. The engine is basically stock with a weber and an exhaust but it might be helpful to have!

 

[jayhawkjesse33]

Great find Gordo! I basically shift manually with my automatic after my engine rebuild a few years ago and even before that, it would just feel a bit mis-timed to me.

 

[wilderbry]

Has anyone looked at "trick out" kits for this transmission. I used to trick out chevy 400 transmissions and it would act like a manual shift with my hurst shifter added. It would shift HARD into the gears with the modulator. The kits back then were like 25 bucks.

 

[The Scifi Guy]

I found a reference!

Harold

P.S. Actual BWD part number.

Okay, in the first link, if you read further I bought the type Wrench bought and it turned out not to be adjustable. Also, that thread was from 10 years ago.

The second link isn't giving me anything on Ebay and the guy never used it. I suppose with some searching I might be able to find that particular adjustable TH180 modulator, but where's the indicator that it is for an Opel. The adjustable modulators came out after our cars were made, so I would think that any part number linking an adjustable TH180 modulator to an Opel is questionable.

So the questions are:
Of the 6 that I found, and I've found some with no stripes at all, so there may be more varieties, how many are adjustable and how many are fixed?
If there are multiple fixed ones, do they come in different vacuum actuation variations?

And the BIG question:
Which one of the adjustable ones would be best for my needs?

I don't need stock non-adjustable modulators, I have 2 of them, neither of them has stripes.

 

[The Scifi Guy]

I just checked with Gil and he doesn't know anything about these adjustable modulators or that there are multiple different kinds.

I also checked Amazon for modulators to see if they were cheaper and found ones with no stripes, stripes in unusual places, one pic that said, printed on the modulator, "Made in the USA", but the ad write up says "Made in China", etc. So, probably stock photographs that have no relation to the actual product and the usual mostly Chinese rip-off krapp that you can't trust one bit on Amazon.


I seem to recall hearing that "manifold vacuum can be affected by spark timing". Can anyone confirm or deny this?

 

[The Scifi Guy]

I know that the answer to all this will never come, so I bought three $40 ones that were all supposed to be adjustable in green, blue, and purple striped varieties, two with double stripes, all with different part numbers.

 

[hrcollinsjr]

@ O'Reilly's Part # 747020 Line: PIO

Harold

P.S. I did read that you received a non-adjustable modulator, that's the reason I added the second part number.

 

[jayhawkjesse33]

I wondered if the different colors were meant to signal a different level, so the unit itself wouldn’t be adjustable, the interchange of these different ones would make the transmission “adjustable”

 

[Young Gt Lover]

I wondered if the different colors were meant to signal a different level, so the unit itself wouldn’t be adjustable, the interchange of these different ones would make the transmission “adjustable”

I was wondering if that wasn’t the case. That makes sense.

 

[The Scifi Guy]

Different level of what is the question. The stripes obviously mean something, but what is that something? I haven't found anyone or any place that can give me an answer.

Are certain colors for large engines, small engines, powerful, weak, big displacement, low displacement, high rpm, low rpm, etc.?

Almost none of the sellers indicate what cars they are for. Some sellers said this particular type was for Holdens, Commodores, etc. ; Another seller's particular one was for a specific Peugoet ; Another said it was for Post Office Jeeps and Chevettes ; Another said specifically for a Suzuki Vitara ; and another said "For all 4, 6, and 8 cyl vehicles".

Which one do you choose for a jacked up 2.4?

With nothing to go on, I had to use the shotgun approach and buy them in all the colors.

 

[hrcollinsjr]

Different level of what is the question. The stripes obviously mean something, but what is that something? I haven't found anyone or any place that can give me an answer.

Are certain colors for large engines, small engines, powerful, weak, big displacement, low displacement, high rpm, low rpm, etc.?

Almost none of the sellers indicate what cars they are for. Some sellers said this particular type was for Holdens, Commodores, etc. ; Another seller's particular one was for a specific Peugeot ; Another said it was for Post Office Jeeps and Chevettes ; Another said specifically for a Suzuki Vitara ; and another said "For all 4, 6, and 8 cyl vehicles".

Which one do you choose for a jacked up 2.4?

With nothing to go on, I had to use the shotgun approach and buy them in all the colors.

The number I listed in my last post is listed as fitting Opels and has a dual blue stripe.
The different colors indicate the firmness of the shift when it shifts.

Harold

 

[Timbo]

Can you make up a test jig that you can apply vacuum to one and see at what level it activates. With your setup, ones that trigger at higher vacuum levels wouldn't work.

Shouldn't your torque curve determine the shift points? Shifting when torque is low would make the car feel flat. I'm not sure how you would match your torque curve to the vacuum profile.

 

[The Scifi Guy]

Can you make up a test jig that you can apply vacuum to one and see at what level it activates. With your setup, ones that trigger at higher vacuum levels wouldn't work.

Shouldn't your torque curve determine the shift points? Shifting when torque is low would make the car feel flat. I'm not sure how you would match your torque curve to the vacuum profile.

At this point it's all a big guessing game. I noticed that my tranny was waiting until about 3500 rpm to upshift for about 2-3 weeks before I started my FI project. Then when I started driving the car with the new FI it wouldn't shift at all unless I eased off the gas pedal a bit, which would bring the vacuum up from zero to 4-5Hg's, then it would shift as normal.

Is something wrong with my tranny? The modulator? Vacuum leak somewhere? Some quirk of too much spark advance causing low manifold pressure? Throttle bodies too big? It's anyone's guess.

I just completed a serious vacuum leak search and destroy mission and replaced all my hoses, modulator, head-to-manifold gasket, TB-to-manifold seals, etc. I did find some looseness of the hose at the modulator. It could be as simple as that being the cause. But I want to hedge my bet and look into the adjustable modulator thing. I didn't think they existed, but then I found that MOST of the TH180 modulators for sale are now adjustable and there are multiple different types.

I suppose I could cook up a rig to test them and I am curious, but I can't imagine how to make a test rig to do it .

 

[Gary]

Why complicate things... (and it's chrome!)
Vacuum Reservoir

The "Dual Ram" setup in my 24v wagon has a canister that provides enough vacuum to move a valve that switches the runner length at WOT.

 

[rrossjr]

Why complicate things... (and it's chrome!)
Vacuum Reservoir

The "Dual Ram" setup in my 24v wagon has a canister that provides enough vacuum to move a valve that switches the runner length at WOT.

Check out one of the reviews for this part.

 

[heliman]

It's been over 40 years since I worked in a transmission shop, so I don't remember what the color codes are. For some reason I'm thinking black is the lowest spring rating, but don't hold me to that. What I can tell you is what the color code refers to. It's the spring tension in the modulator. The stiffer the spring the more vacuum required for the shift and the lighter the spring the less vacuum required. But regardless the spring rate the adjustment works the same way on all. There is another spring behind the adjustment screw, so backing the screw out lowers the required vacuum and turning it in raises the required vacuum for the shift.

 

[The Scifi Guy]

It's been over 40 years since I worked in a transmission shop, so I don't remember what the color codes are. For some reason I'm thinking black is the lowest spring rating, but don't hold me to that. What I can tell you is what the color code refers to. It's the spring tension in the modulator. The stiffer the spring the more vacuum required for the shift and the lighter the spring the less vacuum required. But regardless the spring rate the adjustment works the same way on all. There is another spring behind the adjustment screw, so backing the screw out lowers the required vacuum and turning it in raises the required vacuum for the shift.

OH! THANK YOU SO MUCH! That was my next dilemma that I was going to post about. I had no idea which way to turn the screw to adjust it for my needs. Two of them have arrived so far, third one is on the way.

Now, with all 3 versions in my hands, which color and combo of stripes would likely be the best to use for my needs? I know that you probably don't know off the top of your head, so this is just a general question that remains for someone to find the answer to.

I am now convinced that spark timing and other factors related to manifold vacuum are the root cause of my tranny's reluctant shifting. I had not connected a vacuum compensation hose from my regulator to the manifold on my FI project. I did this yesterday and now the car drives much better, revs past 3000 and 4000 without issues, and even shifts better. The vacuum in the manifold seems to have now increased. I had also done major regasketing and hose replacement to make sure that vacuum leaks weren't a factor. It's still not perfect, but the shifting has improved to almost acceptability. Shifting 1-2 is still not happening when it should, if at all, but the shift 2-3 is almost dialed in. Downshifts are no problem.

I fully realize that my desire for an adjustable modulator probably isn't really needed, but maybe it is, due to the high compression of my engine. I bought the 3 adjustable modulators to give me options to help me deal with my issues and make the car work properly as I work through some issues.

 

[Young Gt Lover]

OH! THANK YOU SO MUCH! That was my next dilemma that I was going to post about. I had no idea which way to turn the screw to adjust it for my needs. Two of them have arrived so far, third one is on the way.

Now, with all 3 versions in my hands, which color and combo of stripes would likely be the best to use for my needs? I know that you probably don't know off the top of your head, so this is just a general question that remains for someone to find the answer to.

I am now convinced that spark timing and other factors related to manifold vacuum are the root cause of my tranny's reluctant shifting. I had not connected a vacuum compensation hose from my regulator to the manifold on my FI project. I did this yesterday and now the car drives much better, revs past 3000 and 4000 without issues, and even shifts better. The vacuum in the manifold seems to have now increased. I had also done major regasketing and hose replacement to make sure that vacuum leaks weren't a factor. It's still not perfect, but the shifting has improved to almost acceptability. Shifting 1-2 is still not happening when it should, if at all, but the shift 2-3 is almost dialed in. Downshifts are no problem.

I fully realize that my desire for an adjustable modulator probably isn't really needed, but maybe it is, due to the high compression of my engine. I bought the 3 adjustable modulators to give me options to help me deal with my issues and make the car work properly as I work through some issues.

I might be interested in the one that is best for a “stock” 1.9 with and exhaust and a weber. Do you think it would really be better than stock for my application?