New owner, 1972 Wagoneer. TH400 shift help.

[baileynb]

I know you all want pictures too, but I'm on my table and I can't upload them from here. I'll add them in the thread tomorrow.

Anyway, I picked up a 1972 Wagoneer Saturday. AMC 360 engine, TH400 trans, Dana 18 TC, Dana 30 front and Dana 40 rear. In really good condition overall. Handful of things that need cleaned/upgraded before I'd call it ready for daily driving. My biggest issues are brakes and transmission. As far as brakes, it's 4 wheel drums, pedal gets almost to the floor before they enage but then work pretty well when they do. It has factory power brakes, I'm going to be ordering a disc conversion kit for the front, swap in a master cylinder I pulled from a '79 with factory disc brakes, and replace all the rubber lines. I figure that should take care of the brakes.

My biggest issue right now is the transmission. The seller said it's shifting hard. He changed the filter (and put in a pan with a drain plug, so that was nice of him) and I belive the vacuum module (and there's another in the back seat). He advertised the truck as needing a trans rebuild. The shift takes a long time to happen. I can hear it getting to the limit then around 35 mph it shifts with a big lurch into 2nd gear. 3rd gear takes a long shift with throttle at around 65 with another lurch. Downshift seems fine. Engine idles great as far as I can tell and sounds good other than when trying to shift.

I checked the vacuum line. Someone installed an Edlebrock intake manifold (without EGR) and had the, I think vacuum canister, and trans module on a shared L port and ran a rubber hose between the manifold and the hard line. I installed another vacuum port in the manifold to properly attach the hardline and exchanged the other port with a single barb for the canister. I also had to change out the brake booster line and the breather hose from the oil fill port to the Edlebrock carb air cleaner.

I checked fluid level (engine warm, idling in neutral) and it's at the "add quart" line, so it is a little low on ATF. I did not check for actual vacuum yet at the module. It slipped my mind before. Any other suggestions to check before I drop the trans and take it to a shop? I'm afraid of having it rebuilt to find out something else was the problem.

Thanks everyone.

[Yeller]

Sounds like you have a nice find.

I’d do a few things. first make sure there is actual vacuum getting to the modulator. Do a vacuum test on the engine. Unplug the kick down solenoid, if it has power for some reason it will not shift until the governor shifts it. Play with the adjustment of the modulator (screw inside the vacuum port) to see if it changes. If it is shifting, just late and hard, the only real thing that could cause that is the modulator valve or the kick down soleniod closing.

[baileynb]

Thanks. Where do I find the kickdown solenoid? Not sure if it matters, but it's an aftermarket Edlebrock carb as well, 1406 I think?

Vacuum test is just spraying carb cleaner around ports to see if there's an RPM change, or is there a better way?

Eventually it'll get EFI, but I have other projects to finish/start before doing heavy tear-downs.

[tgreese]

No expert on the TH400 - however, there is quite a lot of diagnostic information in the TSM. These Jeeps used the TH400 through 1979, and the TSMs got better with passing years. Suggest you download the '79 TSM from the Tom Collins site and refer to the section on the automatic transmission.

https://oljeep.com/edge_parts_man.html

TSM.png

The TSM shows a detent solenoid - I presume that's what Yeller refers to.

Welcome from Boston.

[Yeller]

The solenoid is the only electrical connection on the transmission, it is a single flat spade connection. For the life of me I can’t remember which side it is on, but it is just above the pan rail. If connected, unplug the wire and see if it changes.

There should (or was if not) be a switch in the throttle linkage just about love the accelerator pedal that depresses at wide open throttle that activates the solenoid and forces a down shift to first or second gear depending on speed and rpm.

[Herk]

Replacement "small" modulators are adjustable, and the depth is different inside. Make sure there is good vacuum to the modulator. The original modulator had an angle adapter with a linkage piece on the inside. The spool valve on the valve body is designed for this and may not work well with new replacement modulators. The angle adapter is for front driveshaft clearance. You most likely have a model 20 transfer case unless somebody swapped in an 18 which would be a large step backwward.

[tgreese]

Yes, the Dana 20 was the only transfer case offered by Jeep in 1972. No Quadratrac full-time until 1973, and then optional the first year.

The 1972 TSM is available on paper or digital media at RockAuto. Not expensive.

[baileynb]

Ugh, I always mix up T18 and Dana 20 when dealing with Jeeps and Internationals. Yes, it is a Dana 20. I'd ultimately like to swap to a T18 at some point just because I highly prefer manual transmissions, just need to start looking for parts for when I have a proper shop to do the work in.

Regardless, thanks, I will look for the kick down solenoid. I don't see it listed in the 1972 paper manual I have in the automatic transmission section, but it was a pretty quick skim through. A web search shows it should be on the driver side. I'll check if it has power when I check vacuum at the vacuum module.

[tgreese]

DetentSolenoid72Jeep.png

Page 7-20 of the '72 TSM.

[baileynb]

Well, that explains that.

Thank you.

[baileynb]

Checked for vacuum at the module, had pretty good suction on my finger. Next time I go out, would it help to have someone give it a little throttle to see if if the vacuum increases or decreases?

Pulled the only connector I could see on the transmission, which brings me to the question of what controls the reverse lights? Is it in the column? Anyway, I drove it with the switch disconnected. When I first took off, it felt like a smooth shift from 1st to 2nd around 20mph, then 2nd to 3rd around maybe 40 mph. Honestly, that may have been the situation previously. It was once it had gotten into 3rd that it starts having the hard shifts and I'm wondering if it's hard downshifts.

So there are two wires from the transmission, one yellow and one black. The yellow goes directly to the switch on the accelerator pedal. The black goes into a single wire connection with either a faded red or an orange wire. I lose track of it under the dash. The pedal switch has a second yellow wire that runs up to a single wire connector with a green/white wire that I lose track of at the ignition switch. I did check the switch with my Fluke, it opens with the plunger extended and closes when depressed.

I did not check for power at the solenoid with the engine running and it's too close to the exhaust to do right now. Once it cools down (and I do some of that work I'm suppose to be doing to earn my paycheck...) I'll put the Fluke on the connector terminals and check for power with the switch extended and depressed to check for the 12V signal. I'll also look at the adjustment on the switch as I suppose if the pedal hits it too soon it could cause an issue.

If I have power only when the switch is pressed in and I verify the switch only closes with the pedal fully depressed, is it looking like the kickdown solenoid?

Without a tach in the cab to see the RPM changes, I have a hard time tracking gear shifts. At some point, someone did put a tach in the engine bay (connected with aligator clips, yay!). I'm going to remove it anyway, but there may be enough length in the wire to run it through the firewall to use on the next test drive.

[baileynb]

Okay, next update.

So apparently, some vehicle models did have a two terminal body connector. I'm still not sure where the other wire goes, but that's something else to track down later.

Voltage is present at the body connector with ignition in "ON" and pedal switch pushed in. I will say that the ignition switch may need replaced because I have to bump back towards "START" to keep power on that circuit. I don't think that has anything to do with the problem just something that could create a different on in the future.

Hooked the connector back up and pushed in the switch. I don't hear the solenoid click over as voltage is applied and removed. I'm going to have my girlfriend work the switch while I'm under the truck, but I'm leaning towards the likely 50 year old solenoid has failed. There's an Autozone near me that has a Duralast solenoid in stock, looks like I'm dropping the oil pan this weekend.

[tgreese]

You should have strong manifold vacuum at idle. Vacuum will be highest at cruise, and lower when you accelerate. Look on line - there are lots of charts of vacuum signal for use with a vacuum gauge. A vacuum gauge is a cheap and useful addition to your toolbox; Amazon, Harbor Freight, etc.

Kinda hard to figure the backup lights out for a '72 from just the book, it seems. I believe that '73 was the first year for the GM column. This has a combined NSS/backup switch on the column. The wiring diagrams for the Kaiser years ('71 and older) are really sparse and I don't think you can figure it out from that. In '72 AMC Jeep revised the diagrams with line drawings, which may be your best source. I looked at these quickly and there is a connection for the backup lights from the dash harness to the chassis harness, but I did not have time to take that any further. You might use the TSM diagram and follow the backup light wires from that connector back to the switch. It may be on the column; seems likely if the wire originates under the dash.

For the detent solenoid, I suggest you look at the pictures in section 7 to see where it comes out of the case. You should be able to recognize that connector from the photos in the '72 TSM. Suggest you look at the later TSMs for more info on the TH400. The backup light circuit will be different, but the transmission is the same through '79.

[Yeller]

Back up lights and neutral safety are on the column.

[baileynb]

That's what I was figuring. I pulled a column apart in the JY yesterday to get to the turn signal switch (mine doesn't cancel after turning the wheel). There was a single wire with a micro switch on it I'm guessing is for reverse. I believe it's black with yellow stripe.

[Herk]

Your problem isn't the detent (kickdown) solenoid. If it shifted into 3rd at all, that's not the problem. There is a 2-wire connector on the left side of the transmission. One is 12V + from the switch on the throttle linkage, the other is ground. This controls full throttle kickdown or "passing gear" and nothing else. It has absolutely no effect on shift timing or feel, that's the modulator.

T18 is a Borg-Warner 4-speed manual transmission Dana 18 is a transfer case used in Willys era Jeeps. The T18 used in J-series trucks of this era had a special long input shaft and bell housing spacer. These vehicles all used Dana 20 transfer cases, although the input gear splines may be different depending on the transmission. Keep this in mind if you intend to swap. Most 4-speeds came in 6 cylinder trucks. Almost all V-8 Wagoneers were automatic.

The reverse lamps and Neutral Safety Switch are located on the top of the steering column under the dash. Unless you do something to destroy this switch, like taking the column apart without removing it first, they are robust and pretty trouble free. Try starting the engine in low gear. It shouldn't. If the reverse lights don't work, try the fuse and bulbs first.

Everything you describe sounds like problems I have had. First was replacing the big black modulator with the small gold one. When I did this I had to adjust the modulator for the earliest shift so I could get into 3rd at 25 MPH. There is an instruction sheet in the modulator box that explains how to set it. The new ones are a universal part that needs to be adjusted for each application. Second was not realizing that the governor wears out, but I doubt this is your problem. The modulator, regardless of whether it's large (old) or new (small) must use the angle adapter assembly to work, unless you replace the corresponding spool valve in the transmission. Jeeps used a different valve than GM cars because of the angle adapter.

The factory service manual has a very extensive section on the theory, operation, and servicing the TH400. In some ways better than GM service manuals. I strongly suggest you read this section thoroughly and follow the diagnostic procedures. What you describe is an ineffective modulator. The transmission shifts like you are at full throttle because it thinks you are at full throttle.

[baileynb]

It was the detent solenoid. I dropped the pan after I got home from my conference today. The metal mesh piece and attached rubber had come undone and was jamming the plunger on the solenoid. I'm guessing it was causing pressure issues for shifting in general and was preventing downshifting. I think the violent forward jerking shifts were actually downshifts when I was trying to accelerate. I don't know for sure, but it shifts great now.

Since the previous owner had changed the filter and fluid, the trans is practically flushed now with another new filter and another 5 quarts of clean ATF. I added a bottle of Seafoam Trans Tune as well. Not sure if it works, but it was on sale and I've had good luck with their other products. Now I feel comfortable driving it to the emissions testing center and register.

Next task: front disc brake converision. Thanks for the help everyone.

I can't attach a photo at the moment, I'm going to have to get my cloud storage set up.

[Yeller]

That’s good news.

You can post pics that just need to be small enough. I screen shot them or email them to myself to resize them.

[tgreese]

Can you hot-link from cloud storage? I can hot-link from my server, though I usually embed directly in the forum now and let the forum store the picture. 768Kb size limit for embedded photos.

Glad you're on the road. The TH400 was considered very sophisticated in its day, with smooth shifts and responsive performance. Very durable too. More modern automatics have gotten substantially more efficient, but no better in terms of drivability.

If you want to keep your front axle (a closed-knuckle Dana 30), here is an introduction to a junkyard/parts store conversion using the Chevy calipers and brackets http://www.earlycj5.com/xf_cj5/index.ph ... ds/116749/

[baileynb]

I havd a private cloud storage I need to look into setting up. All the pictures are on my local storage drive. That's a Monday bored at work task...

I ordered the kit from BJ's Offroad with a knuckle rebuild kit, which is now in the garage, just easier that way. I grabbed the larger MC and prop valve froma 79 in a u-pull lot and am just waiting on a new rear hose before tackling it.

I'm not worried about the axle itself. It works and I don't do any serious wheeling so it stays until it busts. I considered swapping a later model in, but didn't want mixed matched wheel patterns and risk different ratios.

It passed emissions this morning, so I'll have plates for it Monday. The emissions people were fighting over who got to drive it when...