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© 2000 Brian F. Schreurs
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By the time we were done, we'd determined that the 318 may not be original (based on its serial number); the A-727 automatic was definitely not original, as it is a newer design than what should have been in there; and that the problem we were trying to solve, a repeated clack-clack-clack-clack sound, probably had little to do with the flexplate. We replaced the flexplate (NAPA Balkamp #600-5051), the torque converter (DACCO #526), and the extension housing seal (NAPA ATP #1-2049), also known as the rear seal. The shift linkage has a grommet which should never be reused -- the replacement is easy enough to get at a dealer (Mopar #03575434). We also installed a new filter (Wix #58707), and since the oil filter had to come off to remove the transmission, we put on a new one of those too (Wix #51515).

Lift the front of the truck. Life will be a lot easier if you can use ramps for this; you'll be banging around a lot and the peace of mind is worth it.

The driver-side engine strut.

As one might expect, to get at the torque converter, the transmission is coming out. Don't panic; it's not so bad with the right equipment. To reduce the amount of the mess, drain the transmission fluid in advance. We cheat; we have a fluid sucking thing from Griot's Garage that sucks all but a trace of the fluid out through the dipstick tube. For the rest of you, the only way to get the fluid out is to remove the transmission pan. It's held on by a large collection of 1/2" bolts.

With most of the fluid out, and perhaps even with the pan already removed (if you don't have the sucking thing), you might as well swap the transmission filter. Odds are, you don't change it enough anyway. Our truck has not been with us for too long so it was the first time we'd seen the inside of the pan. It was scary! The sludge was built up beyond the capacity of the filter or the magnet to contain it. Come on people! Transmissions need oil changes too! On the A-727, the filter is held in place with three Phillips screws, perhaps the best design we've ever seen for a transmission filter. We don't entirely trust the press-on type.

The flexplate-to-converter bolts. Access is limited.

Put the pan back on but don't refill the transmission. It's time to get that puppy outta there!

If your truck is equipped with single exhaust like ours was, you'll have to remove the Y-pipe. Our pipe was so mangled that we vowed it would never find its way back on; we removed it along with the exhaust manifolds, intending to put headers and dual exhaust in its place. If you are less ambitious, the Y-pipe can be unbolted from the manifolds, with sufficient application of PB Blaster. They're 1/2" bolts.

With the exhaust out of the way, unplug the battery and remove the starter. Our starter's ground wire was held on with an 11/32" nut and the positive wire was held on with a 1/2" nut. The starter itself was held with an 11/16" nut on the bottom and a 5/8" bolt on the top. The nut fastens to a stud; with the starter removed, unscrew the stud as well (if it will come out).

Remove the oil filter. It's just gonna get in the way later.

If your truck is equipped with engine/transmission struts, remove them. They're two big metal bars, one on each side, which connect the engine block to the bottom of the transmission bellhousing. The bolts on the engine side are 9/16" and the trans side are 5/8". Keep track of which bolt is which; on ours, the passenger-side trans bolt is longer than the driver-side.

At this point, if your inspection plate has seen better days (like ours), it may try to smack you on the head -- the struts were the last things holding it down. There's supposed to be several smaller bolts holding it on, but ours was missing all of them so we don't know what size they are.

Mark the driveshaft so that it will go back in the way it came out.

With the inspection plate off one way or another, unbolt the flexplate from the torque converter. You'll only be able to reach one or two bolts at a time, and you'll probably find that it turns when you apply much force.

The trick is to have a friend holding the engine with the crank nut. Too bad you can't see it -- who knows how big it is? We used two different methods of measuring it and arrived at the same answer: 1-1/4". Method one was to put clay over the nut, remove it, and measure the imprint left in the clay. Then, to double check it, we stuck a piece of paper over the nut and drew lines on the paper with a crayon. The crayon leaves an extra-dark spot where it encounters the edge of the nut, so measure from dark spot to dark spot for the width of the nut.

With a 1-1/4" socket on a breaker bar, an assistant should have no problem holding the engine steady against your leverage as you loosen the flexplate-to-converter bolts. There are four of them, and they are 9/16". When you can't reach any more of them, have your assistant turn the engine clockwise until you can get at another one, and so on 'til you have all four removed.

Remove four nuts per side on the transmission crossbrace: the top two and the bottom two. The middle two can stay put.

Next up is to disconnect the shift linkage. Note that our truck seems to have a mixed-breed linkage more closely resembling that used on 1990-vintage A-727s than anything they would have used in 1974. So if you have the correct linkage, you're mostly on your own. For us, the linkage comes down the side of the truck and hooks to the transmission through a grommet on a bracket. This bracket is held to the transmission by one 11/16" nut, and will be a little tricky to wiggle off. The grommet in question, if it doesn't just fall off, can be pried or cut off as necessary -- it's required to be replaced so there's no point in being kind to it. Then the rear arm, which connects to the transmission shift arm, is held on by a clip which can be pried off.

Unplug the neutral switch and unscrew the speedometer cable (its housing is 1").

The driveshaft has to come out. Start by marking the differential yoke/U-joint assembly. It is important that the driveshaft go back exactly the way it came out. Anti-seize compound gets on everything so it is good to use as a marker. Once marked, the driveshaft is held to the yoke with two brackets; each bracket is held down with a pair of 3/8" bolts. Remove them, push the driveshaft forward slightly, and lower it, sliding it out of the transmission at the same time. Set it aside where it won't get kicked around and cover the splined end if there's any chance of contamination.

Now things are gonna get heavy, so don't let anything from here on out smack you on the head. Lift a transmission jack up under the transmission pan. You need a transmission jack for this. Don't substitute. You don't wanna drop the trans. Hold the jack against the transmission because it's about to take the weight.

The transmission is held up in the rear by a crossbrace. It is connected to the crossbrace with one long bolt; you'll find it hiding in the thick center section of the crossbrace. Both the head of the bolt and the nut are 11/16". With the nut off, the bolt isn't threaded into the mount, so just bang it out with a punch.

The crossbrace is held to the frame with eight bolts. Unfortunately, the bolts are just that -- bolts. They're not welded to the frame or the brace, so you'll have to hold the bolt steady with a 5/8" wrench (it'll fit up there, just keep trying) while removing the 11/16" nuts. Note that as you get to those last couple of nuts, it'd be an extremely good idea to have an assistant holding the brace. It's gonna drop straight down, and you don't want this thing giving you a nose job. It should wiggle out of the frame easily.

The flexplate as installed on the back of the engine.

At this point, you'll know whether you have the right kind of jack on the transmission.

Put a large jackstand under the engine oil pan. Put a piece of wood between the pan and the jack to distribute the load. Get it snug against the pan. Once the transmission is unbolted, the engine will need something to lean on, and this is it.

Unbolt the transmission from the engine. There are two large 5/8" bolts and five slightly smaller 9/16" bolts. The top ones are kinda hard to get at. Deal with it. One of the bolts holds the dipstick tube in place. When you undo that bolt, yank the tube out by pulling straight up. Plug the hole with a rag.

Once all the bolts are off, you should be able to push the transmission backwards a couple inches. You did get a transmission jack, didn't you? When you push back, make sure the torque converter isn't hung up on the flexplate. You don't really want that thing dropping on your arm.

If it pushes back okay, you didn't forget anything. Slowly lower the transmission, watching for interference problems with the linkage and the chassis. Once lowered, roll it out from under the truck.

Spend some quality time cleaning the thing.

Oh come on, you can do better than that. Take another swipe at it.

A new extension housing seal on the back...

...and a new torque converter on the front. Guess which costs more.

After you get bored cleaning the transmission, you can swap a couple parts. First, remove the old torque converter. It's still got fluid in it so be ready for a mess. It just pulls straight off. Set it somewhere to drain. Ours was actually the wrong one -- some genius installed a 360 converter on a truck with a 318.

Now with that big ol' weight removed, swap the extension housing seal, also known as the rear seal. It's on the pointy end of the transmission, and chances are, yours needs replacing whether you realize it or not. They're cheap so just do it.

The old seal must be pried off. This is easiest with a very small chisel guided with light taps from a hammer. Try to pry it out evenly. Some seals have a rubber boot on them, some don't. Either is acceptable although we prefer the booted kind.

To install the new seal, press it into the housing and gently tap it home with a hammer. Use a seal driver or a really large socket if possible; otherwise just be really careful to not let it get cocked in the bore. Press it in small stages.

Back to the front: slide the new torque converter onto the shaft. The outermost part of the converter should sit about half an inch into the bellhousing -- use a straightedge and measure it if you're not sure. It'll slip on the first part without effort, but may require some twisting and pushing to seat fully. Get this correct now, because you'll be doing it again later if you mess up.

Use a pair of small C-clamps or Vise-Grips to brace the converter in position. Hint: if you can't do this because there's not enough bellhousing lip in front of the converter, then the converter's not fully seated.

On the engine, unbolt the flexplate. It's held on by six 3/4" bolts. Install the new flexplate and torque down to 55 ft-lb. Odds are, both operations will require an assistant holding the crank nut with a breaker bar.

Coat the crankshaft's hub detent with grease.

Wheel that tranny back under the truck and raise it to near engine level. The engine has two dowel pins pressed in it; these fit into corresponding holes in the transmission bellhousing. Push the transmission up against the engine so that the pins guide it into place. This could take some serious coaxing, but eventually it'll work. When it does, thread one bolt on each side to hold the transmission in position.

Check that you can spin the torque converter freely. If you can't, then it's probably not fully seated. Remove the transmission and try again.

Bolt the transmission to the engine. Remember to reinstall the dipstick tube when you get to that bolt. If you're in possession of several extension bars, we actually had the easiest time reaching the top bolts from behind the transmission -- but that requires a couple feet worth of extensions. Still, even if you don't own them, you'll find tons of uses for extension bars so it might be worth the investment to get a bunch.

Reinstall the crossbrace. Chances are things have shifted just enough to make aligning the brace a real pain in the neck. If it just won't line up right, try pushing the transmission a little to the left or right. Also check to make sure you're not trying to install it backwards -- on the front, the sheetmetal lip disappears around the center section; on the back, the lip runs all the way across uninterrupted.. Don't forget to install the mount bolt in the center of the brace.

Reinstall the engine/trans struts. On the transmission side, you'll see that one bolt is longer than the other. The long one is for the passenger-side.

With all of the structural components reinstalled, it is now safe to remove the transmission jack and the jackstand.

Bolt the flexplate to the torque converter. You will need an assistant to turn the engine and hold it while you are tightening.

Reinstall the driveshaft. Be certain to line up the marks you made earlier.

A rat's nets of linkage, wiring, and tubing.

Reconnect the speedometer cable. Attach the transmission cooler lines. Plug in the neutral switch. Reassemble the linkage, being certain to use a new grommet. The grommet needs to go on the shaft before it goes through the bracket, because the fat side of the grommet needs to be facing away from the transmission.

Reinstall the inspection plate and the starter. Refill the transmission.

Start the truck. Keep in mind that it will only take a couple of seconds for the transmission to be low on fluid. This is because it must refill a lot of internals that you drained during the course of this project. Get the truck level and pay close attention to the transmission fluid. Top off as needed. Hold the truck in each gear for a few seconds so fluid can get everywhere and check it again.

When you are confident that you have enough fluid, go for a test drive and see what you forgot to tighten! Well, hopefully not.

We thought it would never end, but at last the truck's strange clacking noise is gone! It just goes to show, sometimes you find surpises when you take your vehicle apart. We planned to replace the flexplate; the flexplate turned out to be one of the few parts that probably was not the problem! With the new (correct) torque converter, the truck shifts smoothly and doesn't make any funny noises. And now that we've done this once, future transmission projects won't seem so intimidating.