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the curse of the blown transmissions strikes again

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i tried to find a guideline for the 1-2,2-3 shift points but never found anything.


driving lightly i'm shifting 1-2 around 30mph and 2-3 around 40. if i put some power on it i get a 20 mph 1-2 and a 30mph 2-3 shift.


before i was shifting at like 5mph and 10mph


I noticed if the modulator was too clockwise the trans would not downshift fast enough, so if i came to a slow down before a right or left turn i felt like the trans was in 2nd or 3rd gear and there was no power for a split second then it would down shift to 1st.

when i backed off 1 turn it got better. i must of added about 5 turns to the modulator clockwise to raise the shift points to where they are now.


basically counterclockwise shortens the shift points and softens the shifts.

Clockwise lengthens the shift points and makes the gear changes much stronger.


Contrary to what other internet forums say you can get a HUGE amount of adjustment with just the modulator on the C-6 without messing around with a recalibration to the speed governor.


In all this i learned the Torque convertor has a much bigger role then people think.

Before my torque convertor was much lower stall speed, so it would really slam into Gear going from Park. the engine was getting pulled down a bit as well. with the higher stall the engine is getting less load down at idle, and the higher launch rpms is showing what the engine can do even with a tall rear gear set.


hopefully with some practice i will be able to fabricate the line the way i want it and have good clearance in the tunnel.

i plan to make some test bends and test flairs to see if i can make a tight radius bend to the rear cooler line in the tunnel.


I have some options, i still have a stainless tube cooler set and the 90 fitting but i'm trying to get what i want in it.

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yup that is the fitting i have. they make the reproduction C6 cooler lines with 2x 90 degree bends front and back.

The 71-early 72 cars seem to have the straight fitting on the trans front and back.

The late 72-73 cars seems to have the 90 on the rear cooler line and the straight on the front.

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Jeff Awesome thank you.




Well the 90 degree fitting was a total bust.


My c6 case has a kick out right In front of the rear fitting. So what happens is the 90 is too deep into the case and there is no room to install the flair fitting as it holds right up against the side of the transmission case.


So I went to 5 auto parts stores nobody had anything that would either extend the fitting or even had a comparable 90 degree fitting.


I wasted modifing a spare transmission line to a straight from a 90 degree, and wasted 1/2 tank of gas driving all over the place.


I took the straight fitting and dremeled off 3 threads to shorten it put sealant and put the straight fitting back into the transmission and turned it in as tight as I dared to try and get the fitting deeper into the case and give me more room to install the 90 bend in the tubing.


So mission aborted using a 90 fitting out of the transmission as it will not work with what I have, wrecked a transmission line making it work with the 90 fitting that I would never be able to tighten down.


And I'm back to where I was 2 days ago with the original fitting in the trans hopefully a little deeper then before and waiting on new tubing and a tubing bender to fabricate something.

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well what a nightmare it was today:


5/16" tubing showed up and my bender tools all came in today.


I spent the entire day practicing and making test pieces.


here is what happened I could not create a tube with a tighter 90 degree radius using mild steel.

the mild steel would just Kink over and over.


hours went by and test after test failed. I turned my attention back to the stainless steel line i took out.

Stainless tubing is VERY hard to kink. Thus i took my stainless line and Beat the ever loving hell out of it for the better part of 2 hours.


I made a VERY tight 90 radius bend using the stainless line, then spent another 2 hours getting it in the car and making bend adjustment after adjustment getting it to fit. I finally got the stainless line in and buttoned up at around 10pm. i have a lot of clearance in the tunnel now.


I left the car on jack stands and tomorrow will be a leak test. Cross fingers What a HUGE PAIN IN THE BUTT!

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A little late but here is what you need to fill the tube with before bending. It is a low melting temp material that actually expands to fill the tube so that it will not kink when bending and can be removed with boiling water or a heat gun. We used this in the shop to hold odd shaped parts for machining. Once done you just melted it out and you can use over and over.


They have many different products give them a call and go by their suggestions on what to use for your tube bending.


When a man is in the woods and talks and no women are there is he still wrong??:P


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hey david very cool wish i knew about it.


i tried everything with springs and the bender. Very cool with that filler.





Well HURRAY! my line fix is working perfectly, car is running well and not leaking at the moment. went on a 15 mile test drive came back checked for leaks, everything is dry and the fluid level is correct. So at the moment i finished!


YIPPY i did a thing!



Up next; Get my Digital camera working again(why i didn't take many photos in this mess)

and Rip apart the old trans and see what failed inside it.

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7/10/2015 Fixed my camera.


THE SMOKING GUN- The worst Transmission shop ever, PM me if you want the name of the place to stay away from.


Time to take apart the blown transmission and see what happened.


So i put the blown trans on the bench.


first things first look at the outside.


Turns out this transmission was from a 1974 Ford Station wagon Marquis with a column shift.


this transmission leaked from day one it came back from the transmission shop. Note i painted the case on the transmission when i got it back from the trans shop to make it look nicer, i decided to fake a steel tail shaft paint job on it.




I have not even opened it yet and i can already see MASSIVE grooves in the pump bushings. the input shaft was ok




more leaks



the pan: the pan was pretty clean there was some clutch material but no metal.



Problem #1 The transmission is using a deep pan and a stock shallow filter was on the valve body, not a huge red flag since the pan is filled to the dip stick mark, but could be a suction problem for fluid getting into the pump and going around the transmission.


Problem #2, the end play is in la la land way over .50"



Problem #3 as i went through the transmission all the thrust washers were HEAVILY worn and there were gouges in the drums and mating surfaces.


crap "B" lever and "N" servo bottom of the line for performace.



starting to take it apart



Pull the 2nd gear band



Problem #4, the band is obviously burned unevenly, i checked the drum surface and it was OK, no grooving. however when i flexed the band the clutch material started to fall off. usually you see that on really old bands that have not been changed, Possible transmission place not changing out the band for a new one.


more coming apart










By this point I'm not seeing the Smoking Gun on what caused the transmission to lock up, i am seeing heavy wear and scoring, lots of burnt up clutch sludge.



major problem #5 starts to show its head


This picture shows the Low-reverse piston was incorrectly installed the check valve should be installed facing the pan here the piston is installed about 180 degrees out.


Now the real fun starts.




i pulled the Low-Reverse piston and discovered 5 springs were missing.

oh they were there before the transmission place messed with it. you could see the impression in the rust of where they used to be.


the moron that assembled this transmission just lost 5 of the springs and figured he didn't care, he didn't even out the missing springs or anything just left an entire area of missing springs causing uneven piston engagement.


left me saying ARE YOU KIDDING ME!?


moving on.


Problem #6

the trust washer under the parking brake drum was not stamped down correctly.


i took apart the speed governor and it was gummed up with clutch sludge from the clutch failure.


At this point i started to take apart the drums.

forward drum looked ok, again very worn bushings etc.


next the Direct Drum or called the Rev-High drum.

And BLAMO the Bullet that killed the transmission






Those 3 pictures are of a fused clutch band and 2 steel bands, this is what locked up my 1st gear and my 3rd gear.

However it was slipping so what caused it, the heat needed to fuse everything together?


thus i looked into the direct drum piston.



Major problem #7

it is impossible to see in the photo but half of the correct number of springs are missing.


basically you have 3 ways to install the springs early c-6s use all the springs and later ones use less springs in strategic places



My transmission has 6 randomly placed springs for the piston.


i stopped at this point....


one last thing was the trans placed mixed different manufacturers of clutches in the transmission there was wagner in one, raybestos in the other and unknown in the direct drum because it all burnt up. normally you get a kit and all the clutches come in the kit, they must of grabbed whatever they had on the shelf to put mine together and charge me lots of money.


if you want to see the other epic failure of this transmission place i used go here:




to repair this transmission would cost me around 350$ in materials plus a couple days of me wrenching on it.

it needs new bushings which would raise the cost of repair as well.

in this case i would trash out much of the internals and swap over parts from another transmission.


it can be fixed but at this point i don't see a need for it.


interesting to note;


this 74 transmission has 3 clutches in the forward drum and 3 clutches in the direct drum and 4 clutches in the body.

making it a 3,3,4 transmission


I modified my 73 transmission to use 4 clutches for the direct and forward making my replacement transmission much stronger as a 4,4,4 transmission.


a modern built up C6 can be a 6,6,8 for comparison.



So now the failure has been pinpointed. there were more then a few guns pointed at this transmission one bullet had the fatal shot.



I will be hanging the fused clutches and steels on my wall as a trophy :D

----- One more thing to report ----


In all this i changed from DOT 5 to DOT 3 brake fluid. I did this because DOT 5 was causing leaks all over the place.


well switched to DOT 3 and my leaks have all stopped. food for thought.

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Probably one of the quickie trans shops like aamco or similar. I've sat in training clinics with their techs and they admit they just change out the bad parts and send it back out the door with silver paint. The chance of it failing again in their warranty period being low so it's worth the risk to them $ wise. All the evidence you show above remind me of their work. Not to offend anyone working for them, but I was told this first hand from aamco techs ( if you can call them a tech).

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RacerX pretty much that is what happened in this case, However in addition to the bear minimum work and the silver bomb spray job this transmission place introduced additional failures


* missing springs in critical parts that they lost taking the trans apart.


* incorrect piston orientation


I'm not including the obvious;


* not replacing bushings with heavy grooving.


* heavily worn thrust washers and spacers.


* end play well out of spec.


* not replacing Seals. the seals were obviously all old and brittle and cracked.



I paid for a complete transmission rebuild. i got back a transmission in worse shape then when i sent it for a rebuild.



hindsight is 20/20.


I left the transmission place a bad review about 8 years ago. they paid to have fake posts with 5 stars added to the review page to obviously boost the rating back up.





Every single thing i farmed out on my car that i did not touch myself had to be rebuilt or replaced shortly after.



At this point with some more practice i think i could build transmissions pretty professionally and i could build up some really nasty C-6s with aftermarket parts.


I was also surprised how much i remembered about my 3rd member, the seal i put in started to leak again so i tore the nose off and replaced it in 30 minutes hopefully better this time.



I took additional photos of the super shotty work this place did but you would not know what you were looking at unless you built a trans. just from the outside now with educated eyes i could tell it was a bad trans.

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It's an interesting comparison, but with my endeavors of rebuilding T-5, toploader and Tremec 3550/TKO's I have come to notice many of the same sort of repair ethics you have been pointing out with this C-6 series. Improper repair techniques eg., missing/damaged parts, improper clearances, rattle can rebuilds. The best transmissions to rebuild are those that have never been apart since new. Less chance of anyone getting inside to mess things up.



Black 1985 GT

Yellow 1973 Mustang Mach 1

Black 2012 5.0 GT, 6-speed, Brembo brakes, 3.73's

Wimbledon White 1966 F-100 Shortbed Styleside, 390ci, Tremec 3550, FiTech EFI

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absolutely mike. the best is getting that never touched transmission.


However i found that can be a double edged sword.


on the one hand you have a transmission never taken apart, so you will be the first to go inside and take it apart.


On the other you could be dealing with unseen Accident damage, high mileage, neglect.


I first found a 1972 transmission out of a Q code that had never been opened. problem with that was the transmission was heavily worn, and then sat for 25+ years.

the result was a transmission so locked up and worn out that not much could be salvaged from it. Additionally this transmission had a Cracked case under all the dirt from a previous car accident.


clevelandcoupe was kind enough to provided me a 1973 transmission and another late model C-6 transmission.


the 1973 was out of his running car that he restored and turned into a 4 speed. it had been gone though at some point before clevelandcoupe had it, but it was very well maintained.

the internals were like new with some wear and obvious TLC needed in places. The shifter linkage was removed a few years ago to give to another forum member that needed them.

So the transmission was incomplete. there was some storage damage to the cooling line fittings as well. Additionally damage was done to the valve body during the previous case servicing as it was not a factory original. The previous repair person must of not had access to a Inch pound torque wrench which caused over tightening damage to the valve body requiring some hardware replacement.


the other c-6 transmission was out of a low mileage wreck, the internals were clean however there was mechanical damage. Additionally the cooling line fittings on the case were not usable for a 71-73 mustang application and the shifter linkage was not compatible. This transmission had the strongest internals of the 3.

This transmission was also 100% factory built never touched and had the dip stick seal sitting in the pan from the day ford pushed it in installing the dip stick for the transmission.

the internals were in excellent shape, bushings in perfect condition.


The result was i could not use the late model case as a base to work of because of the differences. The 72 case was shot from accident damage leaving the 73 case as the only alternative. The 73 had good internals with the usual Tail and pump bushings being worn out and in need of replacement.

The 73 had valve body damage during the previous repair done to the internals. I had to swap parts from the 72 valve body to repair the 73 valve body. the shift linkage was transferred from the 72 into the 73. the thrust washers from the 72 were in good shape and transferred to the 73 as well. external line fittings from the 72 were transferred over to the 73.

The lever and Servo from the 72 were transferred to the 73 as they were a much higher performance combination then stock.


At this point i explored the internals of the late model C6, i found the internals were much stronger then the 73 version however i could not use the case, the forward and direct drums were rebuilt and installed in the 73 transmission beefing it up again on top of the servo and lever changes.


all these changes completely changed the end play, the 72 came to the rescue again having a #1 spacer washer to give to the 73 transmission, anything thicker would not be in spec.


I decided to use the 72 Transmission modulator pin as well because it was shorter then the 73. Really this is mute because i installed an adjustable modulator purple stripe.


so i ended up with a Frankenstein transmission but had little choice.


I wanted the 72 to work out desperately because my car is a 72, even though the partial vin would not have matched it would of been a 72 trans case in a 72 car. unfortunately that 72 had so many problems even never been taken apart from the factory that is rendered Parts and junk.


the late model C-6 would of been an even better stronger match however it had so many differences externally that i could not use it either.

It also did not have desirable internal pistons, it used a later anti clunk design without the checkball valves, and a late model plastic Sprang.


I had to go out of my way to order and original metal NOS sprang from Australia.


A lot of difficult decisions had to be made as you can see.


The best transmission would be a lower mileage transmission that was never serviced other then a fluid change, that ran documented well in the last 5 years and was stored well out of the weather with all the external access plugged properly. sampling the fluid inside won't tell you much of anything. Dropping the pan and scraping it for inspection will tell you almost the entire story. Stay away from Spray bomb jobs at the junk yard, unless documented that they ran well when pulled.


I recommend if you get your transmission rebuilt or you work on it yourself 'DO NOT PAINT THE CASE' to make it look pretty. I made that mistake with mine as i covered up a bad spray job and tried to make it look presentable under the car. The paint will cause issues with seals and will effect a future service if needed.


during rebuild you have to clean the case as much as possible the paint will come off and get into everything making the rebuild a nightmare.


A parts Washer is the best thing every, however having one or access to one is rare, Brake cleaner works the best followed by Pure Acetone and a metal brush(brass). in this case C-6 your working with cast aluminum, many parts wash liquids will eat aluminum, typical engine degreasers will also eat aluminum, the first weapon you need to use a high pressure over 2000 PSI power washer. if you have a heated power washer even better!


DO NOT USE RED SHOP RAGS ANYWHERE when cleaning parts, the rags will leave red lint EVERYWHERE and drive you insane causing problems later.


Paper Towels are a VERY bad idea as well.


More expensive but they work perfectly are Micro-mesh lint free towels used for paint detailing. as a Bonus they Suck up trans type F like a sponge. I would recommend buying them in 50 packs as you will burn through them fast.


Wearing gloves is a problem because you will be dealing with brake cleaner and acetone which will eat most mechanics gloves. i mostly went bare handed as the chemicals have no effect on me.


there are quite a few tools you should have i would recommend a Gun barrel cleaning set in your tool box this will get you into all the transmission internals so you can get all the junk out.

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Yes, there are always tricks of the trade that you learn after doing. I stopped using the red rags years ago. Blue paper towels are ok for certain things but I recycle down(wash) my car detailing microfiber rags to use for engine and transmission work. As long as they are not too saturated they keep working pretty well. Far longer than you might think.


I hardly wear gloves for anything other than brake work. They just seem to get in the way more than they help and always break at some point.



Black 1985 GT

Yellow 1973 Mustang Mach 1

Black 2012 5.0 GT, 6-speed, Brembo brakes, 3.73's

Wimbledon White 1966 F-100 Shortbed Styleside, 390ci, Tremec 3550, FiTech EFI

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Or worse you have the gloves on working away, later you notice the pads on the fingers of the gloves have disappeared, you look at the work you have done and you see little bits of the pads contaminating everything you worked on.


I came to the conclusion only wear the gloves when you know your hands will get impact damage. Like your working in a tight space and trying to pop a bolt with a wrench you need full strength and you just know when that bolt pops your hand is going to slam into something hard and sharp. I had gloves on trying to pop the c6 pump out of the Case and got red grip pad material all over the place making clean up worse then it should of been. Live and learn lol

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  • 3 weeks later...

final follow up.


as these donors go to the final resting place.



I finally finished taking apart the 1980s donor trans that i used to replace the internals in my 1973 c6. during dis-assembly back in may i found mechanical damage in the form of a snap ring in the pan. i could not locate where the broken snap ring came from. there are 2 in the transmission that size one holds the rear planetary gear and the other holds the speed governor. When i tore the trans down to junk it i found out it was the snap ring holding the speed governor that had blown apart.


thus the final mystery has been solved :)


so far my home built C-6 is still working fine it isn't leaking (at the moment) and shifts strong and with A LOT more power then before. the TCI torque convertor (Saturday night special) seems to enjoy my engines company as well. the car in general drives so much better and stronger then before that i took it to work for the first time in 10 years.




Vroom Vroom

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Really good to hear everything is working out well now! I like that picture of your car from above, interesting perspective.


I still have a strange shift into third but I think I have to buy a new yellow stripped modulator, the green one is not cutting it.

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I'm using a purple modulator, however it is adjustable. I spent 2 days adjusting it to where i felt it worked well, not sure if its 100% correct.


according to jeffs manual for the FMX



I'm in the ball park for my car as my 2-3 shift under light throttle is around 30mph. i could maybe back off another 1/2 turn.


if your modulators are adjustable then it doesn't really matter the one you install since you can change it, the difference is the diaphragms are different sizes, they made a smaller one for high altitude and the black stripe is for Diesel engines.

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  • 2 weeks later...

I saw this and had to post it.




I hope it helps with any future builds.

  • Like 1



"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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Ha!! No sh*t!! , and I just took the cure!

If you don't have time to do it right the first time, you sure as Hell don't have time to do it right the second time.


Dutch uncle

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