Hello again, picking up where I left off.
Some of the plastic parts were just roasted from heat and age. The downshift connector (downshift is electric and not cable on a TH400) was brittle and just fell apart. One of the extra parts I had to get.
I needed a new speedo drive and driven gear ratio to match the new rear axle gear ratio change. Plus the old speedo gears were brittle as well.
The only other hard parts that needed changing were the two large thrust washers in the planetary's. The TH400 had Torringtons in the other key locations, had GM rollerized these two as well the transmission would be considered rollerized and it would help reduce parasitic loss.
You can see the old washer in the middle has just about all the copper worn off and it was steel on steel. The reason why these wear is because the planetary's gears are cut on an angle to reduce gear whine. The problem is under load the angle cut gears either want to push away or suck together depending on power flow and the little washer in the middle get sandwiched, rather hard, between two rotating parts of different speeds or between the fixed case and a rotating part. The heavier the vehicle and/or the more torque the engine has the more the transmission suffers on parts like this.
I flipped the steel case saver washer/spacer around to a good side and used that with the new copper plated thrust washer.
This is where one of the large washers that wore down goes.
Then that whole assembly can go into the case.
This is the rear band and only comes on in reverse and LO (1) range. It should have no wear unless you're towing something heavy and using the transmission as a brake to slow you down constantly. Since I don't, this one doesn't have wear. If it's worn it could also be from slipping which usually means low pressure and you have to diagnose that further.
This was the other heavily worn thrust washer and its replacement. If I was keeping the transmission I would rollerize it like I did the C6's and just rid the transmission of these.
This washer is next down in the hole onto the planetary with its tabs facing down. I use Vaseline to hold things together.
Sun gear and shaft go in next.
The forward planetary assembly goes in next.
Everything should mesh together nicely.
The centre support (right) goes in next along with the snap ring. The centre support also contains the piston that engages the intermediate clutch.
The snap ring has yet to be installed but if everything is set in place correctly the snap ring should fit right in.
There's a black 12 point bolt with a through hole all the way through it. This is tightened next and help holds the centre support. The hole through the bolt allows the pressurizing of the piston in the centre support. The holes to the left and right pass through the centre support unto the rings and pressurize the direct clutch when needed. The piston in the direct clutch has two areas. One for 3rd gear and then using both for reverse as reverse has a higher ratio gear than 3rd so you need more surface area to squeeze the clutches tighter to keep them from slipping.
This is the intermediate clutch (2nd gear) and probably takes the worst beating. Again about half the life left and still serviceable so back it went. There were a couple little hot spots, but nothing to get excited about.
The small band and forward clutch go in next. The small band only gets used when you select 2nd gear manually. This is 2nd gear with engine braking and should only be worn if you're using the engine to slow you down with a heavy load constantly.
Slowly getting there.
Had to the buy the entire thrust washer kit for the two I needed so I replaced all the rest even though they really didn't need it. What the heck. This is the forward clutch assembly and it goes in next.
You can use a punch if you're careful to rotate the forward clutch till all the teeth in the clutches mate.
To set the total end play you buy a selective thrust washer kit. This select washer thickness goes on the front pump. The two old ones on the left were worn a bit and the black ones come in the kit and are new. Now I end up using two of them because I am using an earlier style direct drum (for the higher capacity one way clutch) and the stack up dimensions are that much different between the years of TH400's.
The procedure is pick a close selective washer, use the new pump gasket, lightly torque the pump into place and for me I found inverting the transmission and letting all the weight of the internal parts push forward was much easier, then I zero the gauge.
Then I can stick a screwdriver in the front and lift up on the forward drum against the case and measure the end play.
The allowable end play GM gives is rather generous, however I don't like clunky transmissions so I try to get end play somewhere around 5 - 8 thou. In this case I had to lightly sand one washer to get me there. Yes I was lazy and didn't use the mill. Like I said if I was keeping the transmission I'd be doing a whole lot more to it, this will do as long as you sand evenly.
Once the end play is set the pump can get torqued down one last time with new sealing washers from the seal kit.
The rotating guts portion is complete.
Changing the seals on the accumulator and servo piston. The accumulator seal was so shrunken it wasn't even touching the bore inside the servo. Like I said, age kills a transmission just as much as mileage does.
Another accumulator/servo assembly to change seals on.
Gasket and spacer plate.
I didn't cover it but the whole valve body was taken apart, cleaned and each valve checked for smooth operation and not hanging up in the bore.
There are two different detent solenoids used (forced downshift). The open frame ones like this one do not need the metal gasket in the kit. Don't use it for this type of open frame solenoid.
I only use Wix filters as they are rated as one of the best.
Bottom end done.
The governor was cleaned and checked for smooth operation and installed.
The old modulator was checked with a vacuum gauge pump for leaks and it was fine so it was reused.
Assembled the extension housing and pan.
Here's a neat comparison to a C6 with a FE big block bolt pattern for one of our galaxies I did. This C6 was one of two that got the full treatment. All Red Eagle frictions, Kolene steels, I machined the drums for a higher friction steel count, wider Red Eagle band, rollerized the entire transmission (no more high friction flat thrust washers) and a custom made full size torque converter with a 2400 flash stall. All that means it behaves like a regular torque convertor would under normal driving conditions but step on the fun pedal and it will flash up higher putting the engine back in the power band sooner. Plus even the torque convertor is rollerized.
It's a nice setup, drive the car normally and it behaves like a stock Grand Marquis with smooth shifts, step on the throttle and the engine flares up with torque multiplication to help plant you in the seat. The 390 in the Ford I built is rated just north of 500 horse at 5600 RPM and completely mild mannered below that with a smooth idle. Fun car.
I will eventually do something similar but with a higher horsepower for my Caprice Classic.
And there it's nestled back in its home.
I've been driving the car as my daily driver once more for 3 weeks now, doesn't leak a drop of ATF, reverse works at any temperature and the shifts under normal driving are luxury car smooth with the seals on the accumulators changed. Floor it and it will still bark the wide 255 rear tyres on the 1-2 shift. For me this is exactly how I like my transmissions. Couldn't be any more happier. Well I could be if I had the 4L80E in it.
Speaking of which here it is.
These darn things are really hard to find in 2wd and not with a diesel bolt pattern. With the help of a good friend I got lucky and found this little gem for 380 bucks. It will be completely torn down and much will be done to it, including a wide ratio conversion similar to that of the 4L60 (700R4)/E transmission.
I did some preliminary homework and if you're looking for one you want a 1999 or newer. The majority of the fixes from the early years have been implemented in the 1999 models. In other words, most of the bugs are out of it.
This one came from a 1 ton with a gen VI 454 and it will bolt right up to my old Mark IV 454 in the Caprice Classic. The 1999 non diesel also sports dual pattern (extra bolt hole at top) for the newer LS engines as well.
I will say one thing, this is one heavy back braking transmission. It makes the TH400 and C6 feel very light indeed. That darn torque converter feels like GM filled it with lead. I did some online poking around the single clutch converters are 60 pounds and the triple heavy duty clutch converters are around 80 pounds. I think this is the heavy duty one as it weighs a spinal disc popping stupid amount.
Thanks for sticking around and reading all of this drivel.
Hopefully if anything it inspires someone to want to tackle their own projects, be it a transmission or anything really. I'm not a mechanic, just an electrical engineer by college and trade. If I can do it, you can do it. It just takes patience, common sense and dedication.