How hard is it to rebuild an a518 transmission?

The transmission behind the Cummins in my '93 d350 finally gave up. I had it rebuilt 150,000 mi prior, and the guy beefed it up with some modifications and Kevlar bands and red clutches or something like that. That 150,000 it was always heavily laden, towing the race trailer, or hauling the world's largest production truck camper, or both. So it did pretty good I think.
But now it needs to be freshened up. I have never rebuilt an automatic transmission before. I've done plenty of manual transmissions, engines, rear ends, etc. But the automatic always seems like a mysterious thing.

So should I try and tackle it myself? Where do I start, where do I get the parts, what parts do I get, how long will it take me to do it, do I need any special tools?

Thanks, Joel

I would think that would be a great candidate for a NV5600…… I’m sure Jeff would help spearhead that project!

There are some special tools for the OD section, and a few others for compressing the front clutch. Does yours have the frame mounted trans cooler with the thermostatically controlled fan? Many trucks of that era had them installed due to the less than stellar cooling capabilities.

My 47RE is all stock/factory components with the exception of a triple disc lower stall converter and a valve body kit from Goerend transmission in Iowa. It’s served me well for 163k and the pickup rarely moves without the race trailer or boat in tow.

https://goerend.com/

It does have the frame mounted cooler.

Explain “gave up”.

What does it do, or not do?

And how much does the rig weigh as shown in the image.

I was on my way home from a 700-mile road trip a couple days ago. I had the camper on and the trailer. When I was on my way home, about 200 some miles away, I noticed that the trans temp was running a little high. Usually with the fan on it runs 180 but it was at about 215. When I stopped for fuel I checked the trans fluid and it was two and a half quarts low so I filled it. About a hundred miles later I noticed the trans temp was high again so I stopped at a rest area and checked it and it needed another quart. So I put one in. It also was dripping out of the front of the transmission, I crawled under there and tightened up the pan bolts and checked for any leaks in hoses, but it looked like it was coming from higher up in the bellhousing area. I figured it must be the front seal. Then when I got about 13 mi from home I noticed that the temp was quite high probably over 225 and it was getting slippy where the RPM of the engine was high for the road speed. Especially in second gear. I was out of transmission fluid so I headed towards the nearest gas station to buy some transmission fluid. Before I could get there it started slipping so bad that it was barely drivable at 25 mph. I shifted into low range and into second, and flipped it into overdrive and could maintain about 20 mph, then it started slipping worse. I pulled over in a parking lot that was a mile and a half from a gas station and dumped 2 qt of motor oil into the transmission to try and get me to the gas station. When I got there, I bought three quarts and topped off the transmission. But still I couldn't get it over about 30 miles an hour. So I limped it the 5 mi or so to get home. I think it slips worst in second.

Ouch….. I’d say you’re going to learn. Factory service manual will be your friend.
Monitoring temp in the pan sump?

The only real 'special tools ' required are for the OD unit .
Otherwise its not bad at all .

Grab a manual and take notes . Any questions ask here . But it sounds like the front clutch is going / has gone away

Previous post with lots of info

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2771867/1.html

What axle ratio?
What does the whole rig weigh as pictured?

I’d hope 4.10….. that’s a hella load for that combo

3.54 gears, about 20K depending on what's in the trailer.

Guess I’m one to talk… we’re about 18600 combined and 3.5 gear…. But I have the lockup converter on my side.
Rapid fluid loss from bell area conjures up thoughts of cracked converter drive hub or pump bushing seizing to hub.

WHen I had the trans done last time, I had a DTT 89 converter put in. It has been awesome, so much more efficient than the original mush.

You can make the trans live bit you might be further ahead if you went to the 3.7 or 4.1 ratio and add lockup to the trans.
Besides the weight you are pushing a lot of air.

Not hard at all to add, and going through the trans isn’t either.

My guess is you wounded the pump seal. Probably from so much heat it’s harder than a honeymoon pecker.

I got 150,ooo miles on the last rebuild. If I can repeat that, it's more than good enough. I doubt the rest of the truck will hold up for another 150k, nor will I own it that long.

Understood.

Sweet looking truck/rig.

My fuzzy memory is about 75% sure that in the 1996 to 1998 period Chrysler put out a Technical Service Bulletin saying that the “improved life” design front seal in production year 1994 to 1996 46/47 automatic transmissions was defective compared to earlier design seals. I remember at the time my 1995 46RH was dripping Trans fluid and it steadily got worse.

A good converter is definitely a game changer on these rigs…. and lockup would be sweet!

I’d also pay close attention to the line psi when you’re done and the guy I got my stuff from was pretty adamant about keeping the rpms over 1500 due to fluid volume issues.

Goerend doesn’t build units anymore, but there was a guy in MN that took that duty over from him. Can’t remember the name, a call there might get you that info if you’re in a time crunch.

Well we have had time to remove and inspect….. wondering how high the Minnesota weeds have grown around the ole pickup

Well, fortunately I figured out the transmission seems to be ok. There was two things wrong. When I went to start it to move it and uncouple it from the trailer, I discovered transmission fluid spraying at a very rapid rate from a hose that extends back to the rear transmission cooler. The hose had worn through where it was rubbing on the frame rail. I was a little puzzled, because I knew that it was not doing that when I crawled under there and inspected when I was on my way home from the last road trip and the problem started. But I fixed the hose, filled up the fluid and took it for a drive with the camper and trailer still on it. I drove it hard with the pedal to the metal through all the gears to make sure there was no slippage. Everything seemed fine, so I figured hopefully this is the end of the issue. Then when I uncoupled the trailer and backed to the truck into the pole barn, I noticed a trail of transmission fluid on the floor. So I crawled under there and saw that it was dripping from near the front of the transmission, where I had seen it while I was on the trip. So I took the camper off, put the truck on the hoist and cleaned everything up really good and started it up and looked up in there with a mirror and a light. I discovered that the brass fitting that threads into the side of the transmission was leaking, the fluid was collecting on the little lip above the oil pan, and trailing forward and dripping off up towards the front. That fitting has a big steel pipe coming off of it, then on the end of that pipe is a big brass tee with two sensors on it and a brass fitting for the hose to continue back to the cooler. One of the sensors is no longer in use, so I'm going to get rid of the tee to save weight. I think all that weight on the end of that pipe, on that little brass fitting threaded into the transmission case is not a good thing. So I'm in the process of doing that. Then I think it will be fine. I hope.

So my theory is that the little leak developed when I was on the trip and caused my initial concern but adding a a couple quarts was enough to get me 200 mi.. Then when I got about 10 miles from home or so the hose rubbed through causing the massive leak which essentially stalled the truck. But since it was dark out by then I didn't see the massive leak.
Thanks to everybody for all their help and suggestions. But I'm glad I didn't have to pull the transmission!

Undercar inspections are a good thing on older vehicles. Every car that comes through my shop gets one before the works starts. You might be amazed at the number of things we have found just waiting to cause a problem. We have also found issues ( normally rust) that caused us to recommend not proceeding with any work short of a complete restoration.
glad you found the issue

The hose that rubbed through was actually replaced this year, and routed the same as the old one. I had a hard time finding any half inch hose rated for transmission cooler duty. Apparently the new foreign-made hose does not have anywhere near the abrasion resistance as the original hose. Last night I picked up some 3/4-in corrugated split tubing to surround the entire hose to prevent any more rub-throughs.

is that "T" gizmo the thermostat that partially blocks fluid flow until the transmission warms up ?

Seems like back in the day the “slow” leaks would lead to more damage than a sudden loss of fluid where the vehicle stopped moving…. That said we had an old international travel all with a 727 that quit moving due to low fluid more times than I care to think about. Throw 2-3 quarts in and away we’d go!