Hi all, I've got a 79 D100 Stepside that I'm slowly getting into running shape. One of my next projects is going to be tackling the auto transmission fluid leak. If I fill the transmission up to the appropraite mark on the dipstick, I will get a major leak until it leaks down to a certain level. I would estimate I lose about a quart before the leak slows. Even then it never stops completely, it just slows. So, I know to really diagnose this, I need to really clean the trans and surrounding areas, and then check for the leak on a clean surface. Right now there is so much leakage all over the place, you really can't tell where it's coming from.

One thing I know is missing is the speedometer cable. Could that be the source of my leak? I'm not 100% positive which trans I have, I know the engine isn't original. Build tag says 6 cylinder and A727 trans, but it currently has a 318. No telling what else has been done to it.

I guess my major questions are this. Could the missing speedometer cable be the source of a major leak, and if not, what are the other likely fail points.

 

There are 3 sets of numbers on the side of the pan mounting flange on the drivers side. First set is the part number, the second set is the build date, and the last is the serial number. The dealer can ID the transmission with these numbers. The torqueflite trans usually leaks from the pan gasket, the dip stick tube, the front or rear seals, the speedometer, and the shift lever. There is a seal and an O-ring in the speedometer adaptor. A missing cable itself should not be the problem unless the gear inside is also missing. A missing cable can allow dirt to get at the seal and wear it out prematurely.

 

Update on this, and request for some advice.

Looks like I have three areas that are leaking.

• pan gasket
• speedometer
• shift seal

The shift seal is the major leak, but all three need to be fixed. How involved are these repairs, I'm assuming the transmission can stay in place, right? Any words of warning or advice??

 

They can all be done in the truck. Pan gasket is straight forward.

The speedometer has an inner seal and an o-ring outer seal on the adapter and again no sweat.

For the throttle shaft seal (shift seal) they recommend you drop the valve body to remove the seal. You will need the proper procedure to do this or you will have problems. If you are comfortable with pulling the valve body I will post the procedure. I have heard you can do this without removing the valve body by using screws that you drive into the face of the seal and then pry them out and the seal comes out with them. I have never seen this done so I can't recommend it.

 

Seal, that would be great if you could post that procedure up. I looked in my repair manual, but it doesn't list the throttle shaft seal replacement steps. I've never had an automatic trans apart before, so I need all the help i can get!

Thanks so much for your posts on both of my current threads!!!

 

Remove the pan and filter. Remove the throttle lever and gear shift lever. It may be necessary to pry the clamp portion of the levers apart with a big screw driver to loosen them for removal. Remove the e-clip from the park rod that holds it to the detent plate and valve body. Remove the neutral safety switch. Remove the 10 blots that hold the valve body. Keep these bolts in the correct position as they are different lengths and if reinstalled in the wrong position will damage the transmission. Have a drain pan under the body as you remove it as there is a lot of oil trapped in the valve body. Support the valve body as you remove it as the accumulator piston and spring or springs will fall out. Tap the seal out with a screw driver from below. Drive the new seal in from the top with a 15/16" socket. Be sure to lubricate the seal after installation. Assembly is the reverse of removal. The torque for the valve body bolts is 100 inch pounds. I highly recommend you purchase the HPBooks Torqueflite A-727 Transmission Handbook by Carl Monroe. You can buy a used one for less than $10.00 on the net and the clarity of the pictures is great.

If you ever wanted to add a shift kit now is the time to do it. I would also adjust the bands before reinstalling the filter and pan.

 

Just got around to starting on this repair this week, truck has been sitting all winter. So yesterday, I dropped the pan and got a good look at the innards. I did purchase the book by Carl Monroe, but it hasn't arrived yet. So, I have a few transmission newbie questions I hope someone will have the patience to answer for me. I'm going to take SEAL's reply above and break down the steps.

Remove the pan and filter. DONE

Remove the throttle lever and gear shift lever. It may be necessary to pry the clamp portion of the levers apart with a big screw driver to loosen them for removal. DONE

Remove the e-clip from the park rod that holds it to the detent plate and valve body. NOT DONE. Not sure I know where this is. I know what an e-clip looks like, and I don't see one anywhere. Approximately where would I find this? I assume I'm looking around the sides of the valve body, right? Or is this external on the transmission housing?

Remove the neutral safety switch. NOT DONE yet, but looks easy to do, and I have a new one to go back in eventually

Remove the 10 blots that hold the valve body. Keep these bolts in the correct position as they are different lengths and if reinstalled in the wrong position will damage the transmission. Have a drain pan under the body as you remove it as there is a lot of oil trapped in the valve body. Support the valve body as you remove it as the accumulator piston and spring or springs will fall out. NOT DONE yet, but I see the 10 bolts, looks do-able.

Remainig steps not done yet, I stopped until I can find out the park rod step above.

One additional question about the neutral safety switch. My wiring harness is missing, but I have found the the three cut wires tied to the frame nearby. RockAuto had the replacement pigtail /connector, so I'm ready to splice it in. Problem is the new connector wiring doesn't match up wire colors to the three wires coming from the truck's wiring harness. So, here's what I need to know: My truck has three wires (red, black, green/black tracer) The NSS has three pins. Which pin gets red, which gets black, which gets green/black?

 

I would recommend that you wait for the book. There are spring loaded things that if not restrained will go flying and you may not be able to find some of these parts or know how it goes back together.

That being said the park rod runs front to back. It has a spring on the front and attaches to the rooster comb looking plate, that has 5 grooves along the edge, by a shaft that goes up thru the plate. The e-clip is on top of that shaft on top of the rooster comb plate. The rooster comb plate is controlled(rotated) by the gear shift rod. Removing the e-clip allows you to leave the park rod in the trans. You can't see this e-clip from below. You have to know it is there.

When you change the seal for the throttle lever remember that there is one in the trans case and one that goes between the throttle lever rod and the gear shift rod that go up thru the case. You can access that seal by removing the e-clip from the throttle lever rod. Once you drop the valve body you can see it. You must change both seals.

Non of my wiring diagrams for your year show those color wires and the wires on my truck are also different colors. Sorry. Maybe someone else can help with that.

 

Hiram6; I just finished putting a TF1 transgo kit in my truck. It had been a while since I had removed the control block. I would like to amend some of what I told told you when I was working from memory.

The park rod does run front to back but the rod that attaches it to the rooster comb comes down from the top and you can see the c-clip on the bottom of the rooster comb plate, and remove it, if the trans is in low gear.

One thing you should look for while the block is out is whether the shaft housing that is splined and peened to the rooster comb plate has become loose over time and whether there has been any scoring where the seal wears on that shaft. New replacement units are available for about $60.00 if needed.

 

kd tools makes a shift seal remover/installer,kd #2392,its for mopar trans.
i have used it with good results,no need to drop the pan either.
googd luck.