727 Transmission Rebuild and Mount Info

srosa707 · August 11, 2020, 03:50 PM

Hi everyone. Since I've owned this rig its had a typical 70's era vehicle transmission leak. I am not familiar with transmissions so I reached out to a local shop about a year ago and they said its better to just rebuild it than to bandaid it. So this summer when I picked it up from the storage place I noticed a large puddle of oil and finally decided to pull it and rebuild it myself. I just wanted to share my thoughts on this project and share a little info on the transmission mount issue I ran into.

First off, if you are mechanically inclined and have a decent set of tools in the garage, the rebuild is pretty straight forward. To do it properly, I reccomend a transmission jack, floor jack, jack stands, snap ring pliers, hub compressor tool, in-lb torque wrench, and a parts washer at a minimum. I ordered a TCI master rebuild kit, torque converter, deeper aluminum pan, oil cooler, and temp gauge to complete the rebuild. All of the parts were sized for the RV from TCI which was nice. This trans is behind a 318 small block but if I understand correctly, the only difference between the small and big block trans is the housing itself. Also, this trans was a long tail shaft so it was a real pain getting it out of the motorhome. I had to drop the crossmemember down a bit to wiggle it out. My crossmember was really tight so I did not fully remove it. Other than that, its a pretty straight forward process. You can find the rebuild videos on YouTube and they are easy to follow. Take your time, use assembly lube, and make sure everything goes back the way it came out.

srosa707 · August 11, 2020, 03:54 PM

More pics.

srosa707 · August 11, 2020, 03:56 PM

The trans pan does not come drilled so you will need a drill bit and a NPT tap to complete the installation of the temp sensor. This is an easy task if you are familiar with your tools. Just make sure the pan is secured to your bench or vise so it does not move when you are drilling it. Be sure to drill straight. This particular trans pan adds an additional 2 quarts of oil which should help keep the temp down in the unit. I used the original pan while installing the transmission back into the RV. Once installed, I added the new pan so that I wouldnt damage it by sliding it back under the RV.

srosa707 · August 11, 2020, 04:03 PM

And here is the transmission mount that I have in my rig. I looked everywhere trying to find a replacement but was stumped. Finally, I found this website that makes them. Again, my rig has the long tailshaft so I am not sure if the short shaft has a different mount or not. As you can see in the pictures, my original mount was pretty blown out.

http://www.imperialservices.net/Truckpart.html

srosa707 · August 11, 2020, 04:06 PM

A few more things to note. The trans cooler was pretty simple to install. They have several sizes so I just went with the biggest one they had. It comes with the rubber hose and adapter to route in series with your existing radiator cooler. Due to the size of the radiator and location in which I mounted it, I had to run to the parts store for an additional 3 ft. of 11/32 rubber line to add to the unit.

Also, I ordered trans line flush from TCI to clean out the lines going in and out of the radiator to ensure clean fluid would take its place. I also ordered break-in oil and another box of trans oil from TCI to make sure everything was topped off once complete. I should be finishing off the installation tonight after work and hope to head out on our first trip of the season in 2 weeks.

srosa707 · August 11, 2020, 04:10 PM

Another thing: I reccomend you find a good local transmission PARTS SUPPLIER for parts, if needed. The master kit did not come with a few thrust washers or the sprag rollers. I had to source those locally. Luckily, we have a Transtar warehouse in my area which was SUPER helpful when looking for these parts. Your local Napa, Oreilly, etc. will NOT have these parts in stock and will look at you sideways when you ask for them. I also had the case and tailhousing put through a parts washer at the local transmission shop. They were cool and did it for free. This helped clean off all the gunk and crap from the outside and prepped the inside for installation.

Rickf1985 · August 12, 2020, 10:29 AM

The KEY thing to a transmission rebuild is cleanliness. You cannot be too clean. Keep in mind this is a closed system and once done there is no way for dirt to get in so if you keep it totally clean in the beginning then there will be nothing to cause problems when done. It only takes a spec of dirt to hang one of those valves or pistons in the valve body. As far as oil, I have never heard of break in oil for a transmission, I think they got one over on you there since there is no way to get all of that out of there once the converter is full. You can run it through the cooler lines as a "flush" but it really doesn't work that way. No matter since the oil is going to be transmission oil either way. You will have no issues. People always are told they have to change their transmission oil at xxxxx miles. Not so, as I said, the transmission is a closed unit and as long as you do not overheat it the oil remains as good as the day it is installed. KEY words, Do NOT overheat it!!!

Oz · August 12, 2020, 10:38 AM

Awesome! Thanks for sharing! Personally, it looks way to complicated for me.

srosa707 · August 12, 2020, 11:09 AM

Rick, thanks for your input. TCI sells a break-in fluid that is to be drained after running ~30 miles and then refilled with their trans fluid. Correct, you cannot get it all out and this stuff is meant to be ran with their other lines of trans fluid.

https://www.tciauto.com/fluids.html

Rickf1985 · August 12, 2020, 11:46 AM

TCI is a good outfit, I still don't subscribe to break in oil for a transmission but.............

Break in oil for an engine helps rings seat and has a lot of top end lube but I just don't see where there is anything in a transmission that needs breaking in. Like I said, It certainly will not hurt anything coming from them. I have run their transmissions behind 2,000 horsepower engines. I don't know which cooler you bought but the most efficient are the plate and fin. They are more expensive than the tube and fin but work a LOT better.

Mark, They are not really all that complicated. When you take it apart you just lay out the parts in the order they came out. A friend of mine has been doing this for close to 50 years and still does them in his home shop. He will have several transmissions on the bench from a couple or three manufacturers and he will strip them down and be tossing all the parts in the parts washer as they come apart! No separation, nothing, one big massive pile of parts from three companies of transmissions. It is amazing to watch him work, we are talking racing or something (we used to own a race car together) and he is rinsing stuff off and tossing it into one of three boxes. When the parts washer is empty all the parts are in the boxes for the transmission they came out of and he never even broke the conversation. And to watch him put them together was like watching a robot work. Now you have to keep in mind that this guy helped set up the model for AAMCO and all others that followed. He could name his price for employment at any of the major transmission shops but he just was not the type to work under a boss, especially when he knew more than anyone else in the place! So he seldom stayed in one place too long. This is the guy who taught me to rebuild transmissions but I usually take my stuff to him to have it done. I would rather pay him just to watch the show, and get it done and back to me in a couple hours.

legomybago · August 12, 2020, 06:33 PM

I used to help/watch our gear guy do the same Rick. 13 speed...18 speed's....Saginaw 4-speed...didn't matter, throw gears everywhere faster than I could think. I had an auto transmission friend too, who had trails where you'd walk throughout his shop due to all the transmission parts everywhere, could put them together blind folded.