[ProBudz]

Hey all! First time poster, longtime lurker. Anyways, I recently purchased a 68 coupe a few weeks ago and I’m looking for some help in figuring out a problem. I rebuilt the transmission because when I bought it, it was slipping, then a few days later it would only go in reverse. After the rebuild it ran great for a day lol, then it would give me issues with the forward gears after only a few minutes of driving. It seemed to go into “neutral” while in any of the forward gears and the only way to get it going forward again I would either need to put it in reverse for a few seconds or turn the car off then back on. I’ve tried just flooring it to see if it would grab or something, but then it seemed to get stuck at a high rev and I’d have to turn it off because the RPMs didn’t seem like they were going down when I took my foot of the gas. Since the issue I’ve cleaned the valvebody 2 separate times in case the issue was a stuck valve, which there was. I’ve also cleaned the governor, but just once. I cleaned the valvebody again today and it seemed to run good, it didn’t give me any issues until I ran to the store. When I finished shopping no forward gears at all, not even putting it in reverse fixed it like it used to. I’ve checked the fluid multiple times and it’s slightly above the full mark and hot. This was the first time I’ve touched a transmission so I wouldn’t be surprised if I messed something up. Any insight would be greatly appreciated!

 

[ProBudz]

Oh and when I was doing the rebuild I noticed the torque converter had a fairly large dent in it. I’ve heard once they get dented they’re pretty much on the way out

 

[macstang]

Did you put mineral spirits inside the converter, slosh it around in there for 10 or 15 minutes then drain it all out? Hopefully you have one with a drain plug. You have to repeat that until what drains out is no longer dark. The other way is to have it cleaned by a shop that has the machine. Also, did you flush your transmission cooler lines and cooler including if the cooler connection is just to the radiator?

It sounds like trash is running through the transmission and it will find a place to land in there. More often than not it will land in the valve body. A lot of the time, re-builders do not put the governor filter in or back in. If it doesn't have a filter the governor will clog up quickly if trash is running around inside there. One of my kits, just a soft seals and gaskets kit, had a new governor filter in it.

Did you find and fix the cause of the transmission slipping? In addition to the normal causes like a band or clutch pack burned up or clutch seals wore out or band servo seals wore out, low fluid pressure will also cause this and that often points to the front pump but it could also be sealing rings worn out. If you have some scratches and light scoring in the stator channel the gears are in you can polish those out but you should get new gears.

"it seemed to get stuck at a high rev and I’d have to turn it off because the RPMs didn’t seem like they were going down when I took my foot of the gas.". Stuck throttle linkage?

I am not an automatic transmission expert.

 

[ProBudz]

Darn, no I didn’t clean out the converter or radiator. I just left the converter upside in a bucket to drain while I worked on the transmission for a week. That explains why each time I cleaned the valve body it would get gunked up again, just not as bad. Some of the seals were semi hard and cracked when I was pulling it apart. The oil rings seemed worn down, at least compared to the new ones I put in it and the intermediate band was toast. When I pulled it out, it flattened out almost completely straight and the clutches had almost no material on it. The reverse band and Clutches were still in good shape though.

Unfortunately I don’t think my governor has a filter. I got a filter with my kit(small cone like filter that’s flat on the end) but both holes behind the governor are way too small. I did do the air check and heard that annoying sound it’s supposed to make. I also air checked the other components and it seemed to check out, but it was sorta difficult because to determine because I would get a face full of ATF fluid each time.

I put new transmission lines in because the previous owner had cut both lines in 2 different spots and had put hoses on to connect them back again. To flush the radiator, would I just need to take off the return line going back to the tranny and let it run for a few mins? I took off the line going to the radiator to check the pump and fluid started shooting out.

“Stuck throttle linkage” seems right, it doesn’t have the original set up on it and is rigged up with a different setup with a long spring that seems to get hung up.

Thanks for the advice! I’ll clean out the converter and radiator, luckily I do have a drain bolt on the converter, and post back with a result.

 

[ProBudz]

Finally go around to pulling the transmission. Turns out one of those metal rings on the pump was torn up pretty bad. I have a feeling I know how that happened . I did notice a few other things so far that I wasn’t sure about. On the pump, should there be a ball in that hole?

Also,is this bushing installed right? Or should one of the openings line up with a hole on the case for the fluid?

 

[Pony Gaz]

No Ball in the pump at that location. The case bushing should be orientated so that one of the holes lines up with the case lube hole for the output shaft.
When you put the transmission in D from Park or N, the only component that is hydraulically actuated is the Forward Clutch. The holding element in this scenario is the One-Way Roller Clutch in the rear of the case. This will prevent the Low/Reverse (Rear) Drum from turning counter clockwise, giving the 1st gear reduction through both planetaries.
Now if you select Manual Low or 1, the Low/Reverse (Rear) Band is also applied to hold the L/R Drum, thus taking the majority of the weight off the Roller Clutch.
No big deal in the C4/C6 as the Roller Clutch is pretty sturdy. This is another story with the Mopar 727 transmission.
So when you say you have no forward gears, I can only imagine that the hydraulic circuit that feeds the Forward Clutch has an internal leakage, (possibly 1 or both sealing rings on the rear of the Stator Support) or the Forward Clutch itself is toast.
If reverse works OK, the Input Shaft, Pump, Direct/Reverse Clutch & the Low/Reverse (rear) Servo & rear Band are fine.
HTH. Gaz.