My brother has a worn out 1973 904 in his 83 van currently, so I am going to disable the lockup feature on the rebuilt 1983 slant 904 under my workbench and install that on his van and then rebuild the 1973 904.

The '73 S/6 904 should have the earlier PTK

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V8?? We don't need no stink'n V8!!

Crap. Well, I'll cross that bridge when I get to it. I need to get a rebuilt transmission in the van anyway, so I will just dissect the 73 and see what's what.

Reed just use the non lock up valve body on your to be rebuilt trans and later on when you do the shift kit, if the non lock up doesn't have PTK you can find out what part you need to get.
I don't know how you plan to disable the lock up on the 83?


Richard

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Part of Tyrde-Browne Racing

I plan on disabling the lockup in the 83 transmission by inserting a carefully measured aluminum rod into the spring for the lockup piston and thereby preventing the piston from moving. That should allow the torque converter to function as a normal non-lockup torque converter and prevent the transmission from ever locking up. I have read about this being successfully done by other board members.

To keep things as simple as possible and minimize any confusion on my part with regards to swapping things around, I think I am going to take the stock 1973 904, use the 73 904 valve body but upgrade it with the 79 part throttle kickdown if possible (unless it has PTK already, which I think it should), use the v-8 clutches and drums and bands from the 67 transmission, use the rebuilt v-8 67 front pump (if possible), and keep the 73 governor and gears (unless I find that the gears in the 67 were somehow changed to a wide ratio set, but I doubt they were).

So:

73 /6 case
73 /6 valve body (addition of 79 PTK if necessary and possible)
73 /6 governor and gears
67 V8 pump (if possible)
67 V8 front clutch pack/drum
67 V8 rear clutch pack/drum
67 V8 front band
67 V8 rear band/adjuster hardware

If I can get all that put together and if it works, then, at a later date, I will try installing a shift kit.

The 1979 transmission will be completely abandoned (except for the PTK if necessary and compatible with the 73 VB). The 1967 318 case, gears, governor, and valve body will also not be used. It is too bad since I already cleaned up the 79 case and painted it with some shiny chrome paint. (never mind the vise grips- they are holding the pivot pin for the rear band adjuster)



Tranny in a bucket (sounds like a song by the Police):



I think I will take the best of the leftover parts and rehabilitate the 79 transmission as best as possible. I think the rear drum out of the 73 could be used to replaced the damaged one in the 79, and I can get all the rest of the bushings etc... needed to rebuild the 79. With the way my brother's van goes through transmissions (seven in three years, including two 727s), it can never hurt to have an extra rebuilt one ready to go.

Now you got a plan,67 V-8 parts in the 73 S/6 case. Just forget the 79 PTK. Set aside the WHOLE 79 pile of parts until you find another 78-91 lock-up donor. Maybe find a 82-91 truck 904.

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V8?? We don't need no stink'n V8!!

67 input shaft and drum assy, should be the small diameter. Will not work with a 68 up converter. Also the 67 planitary has a different spline count, then the 68 up tail shaft. Be carefull mix and matching 67 and 68 parts.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Argh, thanks for reminding me of that Charlie. The seller said it was out of his 68 Cuda, but the valve body is date coded 67. I'll need to look for a date code and do some measurements on the V8 parts before I go much further. I hope I didn't waste my money on this 67 tranny.

I may be headed to the junkyard to rustle up a mid 80s 904 out of a truck or van...

Even with a date code of 67 on the valve body, it still might be a 68 trans. Check the spline count on the shafts.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Will do. Thanks Charlie.

I haven't had time to pull it apart and count splines and measure shafts, but the trans identification number stamped on the pan rail (PK 2892 029Y 2293 000) identifies the transmission as a 1968 A904-1, originally installed behind a 318 P2 (?), which was in production up to approximately 2-1-68. The parts manual also has the notation that this part was "Cancelled- Service Components."

Can I safely assume that, despite the early production, that this is a 1968 transmission and that the shafts and drums are compatible with a 1973 transmission? Should I be concerned about the "Cancelled - Service Components" notation?

Don't know for sure what "canceled-service components" means.
I would be concerned, that it might be a "left over" 67 trans.
Just count the splines on the front of the input shaft, that will tell you.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Yep, I think you are right. Spline counting party at my place tonight.

27 splines!

So, it looks like the v-8 transmission really is a 1968 non-lockup 904 that has parts that will interchange with a 1973 nonlockup slant six 904. Yay. Now I need to disable the lockup in the 1983 slant 904T, swap it with the worn out 73 slant 904 currently in my brother's van, then disassemble the 73 904, rebuild it, and upgrade the internals with the bits from the 68 318 904. Whew. If I have enough leftover parts I will rebuild the 1979 lockup 904 for a spare or for sale.

Thanks Charlie for reminding me about the spline count!

For everyone else, this is from Alllpar:

"A-904 transmissions from their inception until 1967 have 18 splines in the input shaft. Non-lockup transmissions from 1968 have 27 splines.

Lockup 904 transmissions appeared in 1978, and have 26 splines. A-500 overdrive transmissions also have 26 splines. The output shaft has 25 splines.

If in doubt, count the splines. It saves a lot of headache and stress later on when you might otherwise discover that you have the wrong torque converter or drive shaft yoke."

See more HERE.

So I have abandoned the rebuild of the 1979 904 transmission for now. Instead, I am focusing on getting the 1983 904T in working order for my brother's van. Some brief history on the 1983 904T. I purchased it from a junkyard last year. It has grease pen writing on it indicating it had been rebuilt in 2006. A quick inspection showed new gaskets and clean internals, plus a sticker on a reman torque converter, all suggesting that it had truly been rebuilt. I swapped filters, filled it with ATF+4 and installed a TF-TC shift kit.

Initially, the transmission had a nasty shudder around 30-35 MPH. I posted some questions back then about it and traced the problem back to a bad torque converter. I then had the transmission gone through by a professional shop because the transmission wouldn't kick down on the highway unless the throttle was floored. The transmission shop told me the kickdown was "two inches out of adjustment" (B.S. since I know I did it right) and gave the tranny back to me. The kickdown still didn't work right. I ended up pulling the transmission and installing a stock 1973 904 in my brother's van.

Flash forward to now. The 1973 904 currently in my brother's van is slipping badly and is on its last legs. So I dug the 1983 904T out from under the workbench to see if I couldn't figure out what was wrong with it.

I opened it up and, much to my surprise, discovered that it appears that the 1984 904T has no part throttle kickdown valve body! I took a picture of the 1979 904 valve body next to the 1983 valve body to compare (79 on left, 83 on right):



As you can see, the 1983 part throttle kickdown valve body is clearly not present on the 1983 904T. One of the main complaints I had about the transmission after the shop worked on it was the lack of a part throttle kickdown. Could it be as simple as the fact that the valve body doesn't HAVE the part throttle kickdown valve body? Why would a 1983 transmission be built WITHOUT part throttle kickdown? The part numbers for the main valve bodies on the 1979 904 and the 1983 904T are the same (4130495).

Can I safely add the part throttle kickdown from the 1979 transmission to the 1983 transmission? I think I can, but I want to be sure.

Next, since the transmission had the shudder at 30-35 MPH, I suspect it was related to the lockup feature of the transmission. Is it possible to disable the lockup by putting a rod inside the lockup spring which holds the lockup valve in the low RPM position? SlantSixDan said it was possible HERE. Anybody know the length of the spacer needed or should I quit being lazy and just go measure it myself?

Thanks to all who actually read through this entire post and post an answer.