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I am new to this site although I have read stuff on it for over a year now while searching for cars. I finally got a car and there are several things I may be on here asking you seasoned veterans in the 442 world. I got a 72' 442 W-30 with the TH400 Dual Gate Shifter. Couple of issues. First, on the left slot as you pull down out of park and go past reverse and neutral, are there supposed to be three more positions on that left side? Drive, 2nd, and 1st? Or is there just one position of drive and it shifts itself from 1st to 3rd? I get the right side of the shifter and how it works in a manual shifting sequence as you push it through the gears. Here is the reason I ask. Right after the car came off of the delivery truck I took ownership and got in it to drive it home. It is very cold here right now and the car wasn't really up to temp yet. When I put it in reverse it was a quite hard jerk. It went backwards fine. Then I went down to what I thought was drive. The shifter was almost all the ways down to the bottom of the left slot. It went forward okay driving around the parking lot. When I got out on the street and put the throttle to it, it would not shift. It stayed in what I assumed was 1st. When I got off of the main street I pulled over and messed with it and it seemed like there was only one choice in the left slot for a forward gear. I pushed it over to the right side and went into 1st and same thing, it wouldn't shift from first. I haven't checked the vacuum line yet to see if it's attached or if it's on the thermo switch. But any insight would help a new ignorant W-30 guy.
Last edited by puck4higgs; November 18th, 2022 at 12:27 PM.
Welcome and congrats. I moved your post to it's own thread, rather that dredging up a thread that's been dead for well over a decade.
Are you sure this is a factory-installed dual gate? It sounds like an adjustment issue in the shifter cable.
The first thing you need to understand is that there is nothing magic about the shifter. There is still only a single gear selector shaft on the TH400, and the trans neither knows nor cares what shifter you have or which side of the gate the lever is in. Gear detents in the LH and RH gates work exactly the same. The only benefit to the RH gate is that you can upshift the lever as hard as you want and it will only move one gear at a time. Also, from the RH gate you can't accidentally shift into reverse without consciously moving the lever to the left. In either case, all the trans knows is that the shifter is moving the cable back and forth, which causes the gear selector shaft on the trans to rotate to the desired gear.
I guarantee it isn't the factory dual gate because it originally came with a bench seat. Which means it likely had a column shift in its new form. So I can't say anything else about it because it didn't have any history other than a frame off about 11 years ago. Can't even say if the trans is original. haven't gotten that far yet. So is there supposed to be three positions on the left side below neutral? If there is then I've got problems probably with the cable being being way out of wack.
Last edited by puck4higgs; November 18th, 2022 at 12:51 PM.
To clarify a little, if you put the shifter in D (on either side of the gate), the trans is in DRIVE and automatically shifts from first to second to third and back. In S the trans shifts between first and second only, and you get engine braking in second. In L the trans stays in first and you get engine braking in first. This assumes the trans has not been modified with aftermarket parts like a valve body or shift kit. From the owner's manual:
I guarantee it isn't the factory dual gate because it originally came with a bench seat. Which means it likely had a column shift in its new form. So I can't say anything else about it because it didn't have any history other than a frame off about 11 years ago. Can't even say if the trans is original. haven't gotten that far yet. So is there supposed to be three positions on the left side below neutral? If there is then I've got problems probably with the cable being being way out of wack.
Your car does have an "X" in the fifth position of the VIN, right?
I have done some reading and investigation on the TH400. I think the shifter is pretty close on adjustment. The vacuum is hooked up even though it is tied to the thermal switch on the front of the intake. However, is it true that it typically takes around 4000 rpm or so for the trans to shift on its own? That's a lot!! If that's the case then that's why it never shifted. I didn't have it anywhere near that when I was driving it. Wouldn't that mean that if you were just driving it around mellow like on city streets, it would never get out of 1st? The question back up the thread with regard to it having a manual valve body, I have no idea. I wouldn't think so because everything else on the car has been similar to bone stock. Unless the manual valve body is stock. As I get into the car farther and farther I find more stuff that wasn't done in the restoration. Also, is there anyone out there that has a Tic Tac Tach? It doesn't need to be original. It can be one of the good copies. Anyway, thanks for thoughts.
The vacuum modulator determines the upshift point. At low engine loads (high manifold vacuum) the trans shifts early (at low RPM). At wide open throttle, manifold vacuum is near zero and the trans shifts late (at high RPM). If the trans only upshifts at 4000 RPM or more, then your vacuum modulator is either not properly connected to manifold vacuum or the modulator is not working properly. The first thing to check is to use a vacuum gauge to check the reading at the hose that goes into the modulator when the engine is idling. That should read 15-20 inches of vacuum.
Okay, so here we go. I'm not as fast as some guys doing this stuff but I have to work it in around a lot of other things. Remember how I told you that the car came originally with a bench seat and a column shifter? Well, whomever did the rebuild on this car did a **** job. The more I get into it the more I find that pisses me off and their disregard for detail. So be it, it gives me plenty to do. I got into it and find that they left the lower linkage from the column shifter still attached to the frame and hooked into the trans shift bracket. The new dual gate cable was also tied on to the bracket and they were fighting against each other. So I fixed that problem by getting rid of the linkage and adjusting the cable properly. They had a couple other things screwed up also like the U clip on the cable was on the wrong side of the bracket. Anyway, the shifter actually has 6 definite stops now including park. I have not taken it out for a spin yet because there is no vacuum to the modulator. ZERO!! Right out of the lower of the three ports coming out of the thermo switch on the front of the manifold there is nothing. The plug on the switch is a two prong plug with what looks like some kind of a diode or something jumped across the two connectors. I'm assuming there is supposed to be voltage on the plug. If so do you now what it is supposed to be on each connector or across both? And do you know where the voltage comes from, just in case there isn't any? Is it possible that just that port isn't working, because isn't one of the other ports for the distributor vacuum? The car runs good so I would think it's supplying vacuum to the distributor. I could probably get vacuum else where but I would like it to work like it's supposed to. And without vacuum there is no point in taking it out to test it. Thanks again.
I don't think the transmission vacuum modulator is supposed to connect to the TCV - it should be connected directly to a manifold vacuum source.
The distributor gets its vacuum from the TCV (none, ported source, or manifold source depending upon the engine conditions), and I think that electrical connector is what goes to the transmission.
Last edited by Fun71; December 8th, 2022 at 10:29 AM.
The service manual shows the modulator vacuum line attached to the three port valve bottom port. Do you know where the connector goes to the transmission?
Thanks. It is a pretty good looking car. Sure would like to get this transmission thing behind me. Still looking for some help with why I'm at Zero on the vacuum coming out of the bottom port on the therm switch?
If memory serves, the 71-72 switch is a 4 port switch, not a 3 port switch. The bottom sorta goes to the vacuum modulator line, but in actuality the vacuum modulator line goes to the vacuum port on the intake in front of the carb. There's a TEE in the line that goes to the manifold vacuum source supplying the vacuum whenever the engine gets too hot. So I think what you're missing is the fact the switch is simply tied into the vacuum line going to the modulator but the modulator should have full manifold vacuum all the time. The middle port on the side goes to the distributor vacuum can, and the top port on the side goes to the vent on the back of the carb. The very top port on the tippy top goes to the ported vacuum connection on the front driver side of the carb. And it has a plug for the solenoid is right next to the ported carb port. It keeps the vacuum can from ported vacuum advance from the carburetor unless you're in 3rd gear with a TH400. It's for emissions crap and nothing else. Well, it DOES help if you start overheating as you wouldn't have vacuum advance at idle. If the temperature gets too hot at idle, it'll swap itself to manifold vacuum and allow full advance to occur at idle or basically any rpm, but mainly for idle conditions, which in turn the extra vacuum advance automatically raises RPMs to help flow more coolant and speed up the fan to try and help cool you back down.
Routing looks something like this (although you have the 4 bbl version- this is the 2 bbl setup and doesn't show any electrical contacts):
DISTRIBUTOR VACUUM CONTROL SWITCH
All cars except 350 cu. In 2Bbl. Manual transmission, non-A/C cars will have a distributor control switch assembly. This unit is used to advance the ignition timing when the transmission is in third or forth gear or when high coolant temperatures are encountered at idle.
With the transmission in first or second gear the solenoid is energized, the valve plunger is sealing off port “C” (carburetor), opening port “V” (vent) to atmosphere depleting any vacuum that might be present in the vacuum advance unit. In third or fourth gear, the solenoid de-energizes allowing the valve plunger to move down sealing off the vent port. When this happens, vacuum is directed from the carburetor through port “C” and out port “D” to the distributor vacuum advance.
When the engine coolant temperature reaches 210 degrees F, the valve plunger begins to move upward sealing off the vent port and opening up the port “MT” (manifold). At 218 – 224 degrees F, full manifold vacuum is directed to port “D” (distributor) and the vacuum advance unit regardless of transmission mode.
Thank you sir. I certainly have an issue. The way mine is set up is only with one tube going to the modulator from the the bottom port. There is no vacuum line setup coming out of the manifold. I'm going to have to find a spot on the front of the manifold and put a fitting into it so I can tee the modulator line. Makes sense why I have nothing on the modulator line. With this diagram I can also make sure the rest of the lines are right. If I'm not mistaken I've seen a fitting up front close to the front of the carb that I just need to remove and put a port in. I'll keep you posted. Thanks again.
Unless you care about an optically correct restoration, all that matters is that the vacuum modulator line to the trans is connected to a manifold vacuum source. Any port in an intake runner produces the same vacuum signal.
I got into it and find that they left the lower linkage from the column shifter still attached to the frame and hooked into the trans shift bracket. The new dual gate cable was also tied on to the bracket and they were fighting against each other. So I fixed that problem by getting rid of the linkage and adjusting the cable properly.
I didn't see this addressed by anyone yet, but I believe that linkage from the trans lever to the steering column is the back-drive for the ignition key interlock. With it disconnected, if the steering column gets into the wrong position, you may find you are unable to turn the key to LOCK (to lock the steering wheel) and remove the key. While the key is in the LOCK position, you should not be able to move the shifter from PARK.
The only thing is, the linkage didn't go back to the steering column. It was just the rod that is on the bottom of the setup down at the trans. hooked to the frame. There is a two bolt bracket that mounts to the frame horizontal to the trans. shifter. There is a rod that goes into that bracket and over to the trans shifter bracket. That rod was stuck into the shifter along with the Console shifter cable. The rest of the old column shift linkage that goes up to the steering column is gone. So that rod wasn't doing anything but messing with the cable. I took it off and it moves nicely now. The only issue with the starting and key lock I've had is the switch assy that is mounted to the steering column under the dash. I was under there messing with the kick down switch and the wire for it, and I bumped the switch on the steering column. I believe the switch is called the neutral start & back up lamp switch. I knocked one of the wires off of it and put it back on. However when I got done and tried starting the car it wouldn't start. Knowing that was the only thing I had bumped, I reached under the dash and messed with that switch and the car started. So, I must have an intermittent issue or it's got a problem. Reading about it in the book sounds not very friendly to change. So I'm going to try and make sure it's mounted tightly and the connections are solid first. That's the only issue I've had with the key or key lock. It seems to behave properly in park or otherwise. The old lever arm for the old column shift on the steering column is locked and won't move. I've checked it and it is solid in place. My question would be, how did they build the console shift with regard to the shift lever being locked in park. It didn't have linkage on it, did it. At least I can't find pics of linkage hooked up to it.
Last edited by puck4higgs; December 16th, 2022 at 08:16 AM.
Reason: want to add more
When you got a console automatic, the linkage still went to the column in addition to the trans lever. So when you move the console shifter, that linkage went back to column and moved/rotated the column piece in same spot as the column shift would have moved. That gives you the lockout feature (collar on column would rotate to the "park" position so you could get key out). A stick shift was similar but the linkage went to the reverse lever. You had to put it in reverse to get key out. A lot of these features were removed or butchered over the years, but its available repro if you want to bring it back to factory.
So if the old lever on column is locked in place and the neutral safety switch is on the column, Maybe the previous owner did that to lock it in park on column so the neutral safety switch would always be in the right position to start. If that's the case, it would probably start in any gear. Unless this year has a neutral safety switch in the console versus column.
1970 has the NSS on/in the console 1972 NSS is on the column.
The backlink that is not connected will indeed let you start the car in any gear.
The collar on the column needs to be rotated to the correct position, otherwise, it won't start at all.
1970 NSS shown below
The backlink connects to the eyelet
So, you are saying that in 72' if you had a console shifter, it had linkage that hooked on to the trans shifter bracket back up to the shifter arm on the steering column? And that's how you got the proper setup for the NSS and that was the only way you wouldn't be able to pull the car out of park with the key lock activated? I'll be damned. Doesn't that make the console shifter harder to operate with that added linkage in there? Well, I guess I better get some linkage then. Because the console shift lever does not lock and it moves freely regardless of whether the key is in or not. This just keeps getting more interesting.
70-72 and I am sure others have the linkage is hooked to the trans shifter.
For 70 the backlink just locks the shifter when the key is off.
For 71-72 the NSS is on the column so when you shift through the gears the collar on the column rotates and the NSS when adjusted properly will allow the car to start only when in Park or neutral.
The factory used the backdrive on Oldsmobiles at least until 1988 for floor shift RWD cars. Maybe longer, I just quit paying attention. But yeah, it does put a very small load on the system, but if it's in the working order it should be in, you'll never notice. And you'll get your shift lock and your reverse lights back if the conversion was done properly. Right now, you have a potential safety issue at hand. If you were driving and I was your passenger, I could reach over and lock your steering wheel and take your key out driving down the road.
The only real piece that's different is the lever bracket that bolts to the transmission. The column shift car doesn't have a provision for the floor shift cable, but they all have the provision for the equalizer (cross-shaft) rod.
Below pic is for 1971. Other cars are similar if not exact. Look at Note B. It says "35D55 (console shift) and 35W26 (dual-gate) similar". Basically, all the A-bodies came with this linkage. Even the 4-speed MT cars.
Even the MT cars had the backdrive, although it was hooked to the reverse gear idler arm. Used all the same components as the auto transmission cars. The backdrive on MT is why the columng would only lock and the key would come out in reverse.
Even the MT cars had the backdrive, although it was hooked to the reverse gear idler arm. Used all the same components as the auto transmission cars. The backdrive on MT is why the columng would only lock and the key would come out in reverse.
That's exactly how my '76 T/A 4-SP worked. Not a header-friendly design from the factory, but it worked for decades across most GM RWD cars.
So I fixed that problem by getting rid of the linkage and adjusting the cable properly. They had a couple other things screwed up also like the U clip on the cable was on the wrong side of the bracket. Anyway, the shifter actually has 6 definite stops now including park.
I'm impressed. I wouldn't be messing with the shift cable adjustment if I wasn't such a gorilla when I first got the car. I didn't understand the shifter and effed up the original cable trying to operate it. I bought a new one (with correct part number) and I installed it. I thought I had it adjusted right for years until one time, the car rolled back in Park! Not right and not good. So, ever since I've messed with it. Now, it appears close to the shift selector spots and will only start in Park and neutral but.....it now rolls again in Park!! When it rolled this last time, the car was making a ratcheting type click under the car which I suppose is the park pawl clicking when it's not catching! I'm a bit frustrated trying to adjust this! Most of my previous 60's / 70's cars were manual tranny's and not this finicky!
I commend your ability to find and fix issues!
I appreciate your comments, but I will tell you its been a brutal learning curve. I've worked on cars since I was a kid when my old man had me out there turning wrenches like it or not. Let's just say I'm not afraid to learn and to get elbows deep to figure something out. I'm not afraid to ask about something also. There has been a lot of **** that this car has had wrong or not done at all. It pisses me off that it was advertised as a full restoration about 10 years ago. Maybe, but they cheaped a lot of it and just flat out left details out. It's okay ultimately, because it gives me something to do and it is still a dang nice and rare car. Plus the values just keep climbing, bonus! And I don't want a concourse car because I'm gonna drive it. I am really glad I found this site because guys like you know your stuff and don't mind sharing it with guys like me. I'm grateful. Thanks again OLE442 and everybody else..
Mike
November 18th, 2022 | 12:25 PM
Dual gate question
