TexasJohn55

Leif, My 55 is scattered, I will have to measure components. My 56 is in car so I cannot measure to end of tailshaft but can get a measurement of overall length to rear face of rear bearing support (tail housing). For consistent results, should we measure total to end of shaft, total to end of rear brg support, bell housing depth, center case length, rear brg support length, etc? I think the reaction flange and pump cover thickness is constant, not sure if that is a variable to consider or not. My 55 is .910" plus .315" plus gskts for total of appx 1 1/4". If folks would like to contribute, should we also get casting #'s and other markings noticed on components? How about tailshaft diameter and number of splines? Folks could contribute whatever info they have easy access to, don't want to discourage their participation. MrEarl, it is your thread, what do you want to help you with a more comprehensive chart? TexasJohn55

MY APOLOGIES TO EVERYONE OF YOU. I RECHECKED MY 55 SPECIAL DONOR TRANS AND IT IS INDEED A '56 (aluminum bell housing) AND THE CODE ON REACTION FLANGE IS "P"225, NOT A "T". I'M SORRY FOR THE CONFUSION IT MAY HAVE CAUSED. AFTER LOOKING AT ALL THE OVERWHELMING EVIDENCE POSTED ABOUT DYNAFLOW ID AND CODES, I REALIZED IT WAS LIKELY I DID NOT HAVE A HYBRID TRANSMISSION SO I LOOKED AT IT AGAIN AND I HAD MISREAD IT. THANKS FOR ALL THE INPUT AND I SUSPECT, PATIENCE. TexasJohn55

I think this nails down the codes for 55 and 56 that Leif and MrEarl have been so diligently working on! Now I need to clean up my own mess of posting bad information.That is worse than no information! If I had a tail, it would be between my legs, I'm sorry folks. I have a 55 Special trans coded O171 and a 56 trans coded P225. TexasJohn55 ****I HAVE CORRECTED MY PREVIOUS POST ON THIS THREAD****

Damn! Thats a nice looking car Joe. You like that old-tank? TexasJohn55

Back to what old-tank said, sucking air or vapor lock, same effect-dry pump. My 55 Special wouldn't keep the glass sediment bowl full and sometimes died out. After inspecting every inch of line back to tank, I found one dark spot, sweating fuel but not dripping. After rubbing it off and tapping on it, I had a hole big enough to drip,drip,drip. Rejected the idea of brazing or soldering, , cut out section and spliced with hose. I also like the idea of mounting an electric near tank,leaks would show up pretty quick. TexasJohn55

OK btate, Back to basics. What else was done when engine was rebuilt? Did it overheat before rebuild? When was new cooling system/radiator installed? How does it drive and pull now compared to pre-rebuild? Does it seem to have enough power? Did you have to make major adjustments to carb mixture or idle settings when first cranked up after rebuild? Have you checked intake manifold vacuum at idle? Have you rechecked initial timing with a light? Slow or incorrect valve timing will cause low intake vacuum readings and also affect performance and build heat. It is possible to have incorrect valve timing but still get ignition timing in range (ie: one tooth off on timing gear/chain set) The more information we have, the better the quality of responses to help you. Willie mentioned trans, your cooler was originally hanging off rear of trans and was coolant cooled. Is it still functional,connected, bypassed,replaced with air cooled unit? Just a few items to ponder. TexasJohn55

buick man, I have 2 GM part # references on Dynaflows. What we really need is documentation of casting # relationship to published pn's, as well as the relevence of casting # revisions or suffix #s. My 55 Special has center case casting # 1342992-5 but pn is supposed to be 1389450. My bell housing has casting # 1163913-3 and pn is published as 1163913. We need more reference data to unravel this mystery. TexasJohn55

Grease Monkey, the accumulator looks to be unpainted and it it bolted to the reaction flange, which is aluminum and an integral part of the trans which is behind and anchors the front pump and torque converter. Alot of the pictures I have seen posted plainly show the aluminum reaction flange unpainted.It would seem impractible to paint an unfinished transmission on an assembly line scenario. Just food for thought, I am not an expert in this area but mine appears to be unpainted virgin rusted cast iron. TexasJohn55 **SECOND INSPECTION WITH GOOD LIGHTING (old eyes) REVEALED A VERY FAINT LIGHT COATING OF PAINT ON ALL CAST IRON PIECES** SEE POSTING 2 SLOTS DOWN

Yeah, he's good at that! TexasJohn55

That is hard to judge without a guage that reads actual temperature. Was your electric fan running and at what temp is it set to come on? It should be set at 10-20 degrees above thermostat rating to keep it off unless needed. I would recommend installing a manual temp guage if only temporarily to assess your perceived problem and monitor fan operating parameters,, and to get an idea of what your factory guage is really telling you. TexasJohn55

Hello fellow members, John here from DFW area in Texas. My first car was a 2 dr 55 Special, loved that car. After I left home and moved away, my stepdad sold that car for a paltry sum to get it out of his way, years later I realized what a prize it was and always wanted another. Roll forward 35 years later, I could not afford a 2 dr so I settled on a 4 dr sedan, not quite the same but satisfied that yearning I had for so long! Have had car several years but became disabled from my profession as a diesel mechanic and could not put the money into it I wanted to. I have just settled on it just being a "driver" for now. Just recently learned of the forums and how helpful they could be. Good solid information is sometimes hard to come by but I have found alot on this forum. My 55 is currently driveable, but just barely. It has not been registered in a few years because of the cost for insurance and such when it really is not road worthy for a long trip or anything. I have my original trans scattered for rebuild and a temporary in it so I can move it around. I have 5 grown children and 5 grandsons and a faithful wife of 40 years. (She is amazing to live with me 40 yrs!) Should have posted here earlier, I am still learning how to use the forum. John (TexasJohn55)

Leif, my apologies to you. I am very impressed with your command of the English language. There are alot of "Americans" that don't do nearly as well! I have a rather blunt personality, not everything gets filtered through my brain. Some people find that abrasive and insensitive but it is not intended. I really intended it to be helpful. I really enjoy your posts, the comment was a cheap attempt at humor and I shall not do it again. My best regards, TexasJohn55

:) I can relate to that!! Oh! my apologies for leaving Leif off the list! TexasJohn55:)

:) I can relate to that!! Oh! my apologies for leaving Leif off the list! TexasJohn55:)

Leif, that woul be "MrEarl is right as he usually is" or that he "used to be" which would infer that he no longer is correct. I am pretty sure that you meant the former...............To MrEarl,my understanding also.My question was in regards to my donor car having a 56 trans in it which I transplanted to my 55 Special and being 1 in too long. I'll not go over all that again,but that 56 trans has a T code on the reaction flange and there still does not seem to be a concensus on that application (in my mind). The contributors to this thread have been very helpful to my own understanding, expecially you and Willie, and I don't mean to slight those I did not name. TexasJohn55 ****CORRECTION! I RECHECKED THE CODE ON MY 56 TRANS AND IT IS INDEED A "P"(225)

MrEarl, the trans coded 'T' does have a cast iron housing, doesn't it? Just curious and I know you already know, but it is so I will also know. Did you follow that? Thank you, TexasJohn55

55 Special: short dynaflow, Code stamped on reaction flange is O (letter) 171, casting # on flange is 1166129 2, date code 4-55. Cast iron bell hsg 1163913-3. add this one to your database research. The assembly pn is 1166140 which uses a bushing in the reaction shaft, this pn is unique to the 55 but the casting # may or may not be. (I had previously incorrectly posted that the casting # was 1166140) TexasJohn55

Yeah, and I have 2 55's and neither one has a speck of paint on them, but who knows what is original after 50+ years? TexasJohn55

Shon, There are no "absolutes" on 60 year old cars. Don't take any information for granted as correct unless you find it confirmed somewhere. Some assumptions to veracity may lead you down the wrong path. Old saying about "assume" is true, it is actually three words that will make an "ass" out of "u" and "me". John

Hello Shon, I have a 55 Special, trans failed, installed one from my parts car (55 Century), was 1 inch longer but I modified rear mounting by slotting some holes, moved the differential back 1 inch and bolted all down. Worked fine. Later after doing alot of research, I found out that it must have been a 56 trans because it has an aluminum bell housing which is also 1 inch deeper to front of trans. Someone may have swapped over the high accumulator in put it in the Century. Soooo... it probably will work but is not correct and tires will be a little out of center in rear wheel wells. Do a search in the forums and you may find several threads that will help. Does the 56 trans you found have the same hi accumulator on the drivers side with a linkage arm toward the frame? Did you measure the total length on both? Mine may be a hybrid that was modified to work in the Century, but it does have aluminum bell housing. Interested to hear what you find out. Good luck, TexasJohn55 PS I don't know any history on either of my cars. Apr 13, A NOTE FOR CLARIFICATION: THE HIGH ACCUMULATOR FOR THE 55 AND 56 SHOW TO BE THE SAME PN IN MY GM DYNAFLOW PARTS BOOK, High accumulator PN 1391940 and is unique to the 55 and 56 trans. 57 used a different number. TexasJohn55

Roger that! I will when I pull my spare back out, but I still need the converter depth spec to check my original when (and if) I get it built and ready. Thanks TexasJohn55

Hello members, There is alot of good info in this thread! Allow me to add to the confusion on trans codes stamped on the reaction flange. I own a 55 Special sedan, code on it is O 171, it was failed when I bought the car. The converter was driven into the front oil pump, failed pump and cover plate. I have not determined why and don't know any history on car. I have a parts car, 55 Century 4 dr HT which I removed the transmission from, checked converter depth to bell hsg face and installed in Special. It is 1 inch longer and I modified rear mounting and moved differential back to accomodate. It works fine except is weak holding in drive clutch until it warms up good. That Century had been sitting in a field for many years, trans may have been original, I was surprised it worked at all because I did nothing to it. The code on it is "T". It has an aluminum bell housing which is 1 inch deeper than my special which is cast iron. My original out of the Special also damaged the end of the reaction shaft and damage the bushing from contamination. Quite a mystery not knowing any history! By the way, there is a spec on the distance from the bell housing face to the converter when installed on the trans but I cannot find that info to save my ---! If someone knows that or could measure a '55, I would greatly appreciate it because I am going to rebuild my original and put it back in. Thanks, I really enjoy the forum and all the great information. TexasJohn55 ************CORRECTION! AFTER READING ALL THE DYNAFLOW POSTS, I DOUBTED MY OWN! I RECHECKED MY 55 DONOR TRANSMISSION WITH THE ALUMINUM BELL HOUSING AND IT IS INDEED A 56 WITH CODE ON REACTION FLANGE OF P225, NOT A "T" AS STATED ABOVE. IT WAS NOT A HYBRID, SOMEONE PUT IT IN THE DONOR 55 CENTURY AND UNDOUBTEDLY RAN IT FOR YEARS.******TexasJohn55