tranny shift points

[Guest]

i had my engine and tranny rebuilt for my 1972 buick sklyark. it is a moderately built 455 with 10.6 comp, 235/245 lunati cam grind, headers, worked Q-jet carb, stage 1 heads, performer intake and 3.42 posi rear. <P>it has a th-400 tranny with a 2275 stall. the thing is that the shift points and the launching of the car puzzle me.<P>to get a great launch (great as defined by using the seat of the pants rating system), i have to bring it up to 2500 rpm by holding the brake and bringing up the idle, and then punching it. then it hold first to around 4800. the other shifts are around 5000-5500. <P>when i am driving around town, the car always seems to be in third. it shifts quickly out from 2-3 and i can't feel the 1-2 shift.<P>also downshifts from 20 mph don't seem to be what they should be (again using the seat of the pants method of measure). i think that it is going from 3-2 and not 3-1. at such a low mph, i would think that it would be from 3-1.<P>any insight on this would help. are these normal shifts, does the launching technique sound right for this car with this set up?<P> i do not want to go to a tranny shop that i am not familiart with, the last time i got work done on my car by someone i didn't know, the tranny blew up a few days later.<P>thanks

[Guest grisby]

riv1973, I too am interested in the answer to this thread. I have just about the same combo as you have except I have 9.5-1 compression with a 2500 ATI stall converter on a 72 GS Stage1. I get the same results you do. Just got back from trannie shop having them check everything out after rebuild and they say everything is ok. I cld my machine shop in NY sometime ago and was told that this is normal. I have another friend who also has roughly the same combo but abt 11-1 compression and he has the same scenario and he has over 5000 in his motor by a very reputable shop known for its buicks. I read comments where these Buicks are smokin there tires between gears with these automatics and how they are laying rubber between gears with the automatics on their basic street cars--is this just HYPE or a lot of BS or are these guys hanging around to many Ch##y guys and just giving us stories. My car is fast-dont get me wrong, but I dont think its doing what a lot of people says its supposed to be doing. I've got a lot of help from this and other groups on my GS. Lets see what the people have to say about this situation. <P>[This message has been edited by grisby (edited 09-19-2000).]<p>[This message has been edited by grisby (edited 09-19-2000).]

[Guest]

i know what you mean. when i got my motor back and installed it i expected to rip rubber all over. if i stick it into drive 1 and then put the pedal down, the car almost spins around 180 degrees. but in drive, it is sort of so-so. i am more concerned by the fact that the car does not seem to stay in 1st for very long at all. also my car is "supposed" to run high to mid 12's with this set up. i see all the time these cars with the front end high in the air. and mine just doesn't do that. <P>i have been told that this is how this combo is suppose to work, but i thought that the car would be more powerful in the lower RPM band. <P>also from a stop, with the car launched from 2500 rpm, the thing in fast but from 20 mph on the street, it is not as fast or quick. i am concerned that the tranny is not set up right. i wonder about the down shift switch too. is that suppose to put you into 1 from 3 or jsut to 2nd gear? <P>this tranny and motor was also put together by a reputable buick guy in the north east. maybe some of the other buick gurus on this site can help. i am in med school in philly and i am bringing the car here from my home in boston to work on it over the winter. the street scene here is pretty tough and i would like to do our buicks proud. so any help would be greatly appreciate.<P>and i have the rest of the cam info if people need it to better understand my motor and help with the diagnosis.<P>thanksd<P>john, the buick guy lost in the woods

[Guest grisby]

John, exact same scenario that my friend and I are experiencing. I took mine back to the trannie shop and had them look at the kickdown and they said it looked fine. I hated to leave it there, for I know how they tested it--you could see the marks on the street. If I shift manually --1,2,3 it runs like a beast but my shift points are around 5000 to 5100 to make the tires chirp, but in drive or a start off from drive or what I would call a 20 mph kickdown, it just dont have the punch. I am the only buick around here except for a trailer queen that only goes to shows(he drives it to local shows)that drives it on the street. Granted my inlaw has a LS5 chevelle that I took but it was done shifting manually-hate to see what the outcome would of been if I would of started out in Drive vs 1st. I feel your frustration, and I know these guys on this list will help us out or at least put our egos in the right place.(Hey if we didnt have EGO's we would not be driving BUICKS)<BR>thanks<BR>bill g

[Guest]

Not all th400's will have the same shift points. the valve body configuration varies depending on the car the trans came from.<BR>GS trannys 69-72 were specifically setup so that they would shift to 1st from as high as 35 mph depending on the gearing.<BR>So, your kickdown switches may be adjusted properly and working just fine and you still won't get a 3-1 kickdown.<BR>Go to the passenger side of your trans and look for a metal tag. This tag (if it is still there) will have the year and model of the trans. A 70 GS455 should be a 70BA (BB if a Stage 1) 71 would be a 71BS or BB and 72 72BS or BB (some 72's also were OW).<BR>Now if you converted your cars and got a trans from a Pontiac, Olds or even Caddilac the codes would begin "P" for Pontiac, "O" for Olds and "A" for Cadillac ("C" was used for Chevy).<BR>The tag will tell you what year and model the trans is and can give me an idea of what you have there. With the and letter codes, I can tell you what they came from.<BR>The next item that changes kickdown and upshift points is the governor. A stock GS and most th400's will shift at 4800 rpm wide open throttle. Stage 1's would shift at about 5500 for 1970 and 5200 for 71 and 72.<BR>It is also not unsual for a modified car to shift at different points out of 1st and 2nd.<BR>A governor modication kit from B&M can help correct this as well as just grinding metal off of the inner weights to get the shift points you want.<BR>There is much much more I can go into on this and it can get lengthy for this post.<BR>I am not sure of your cam specs on your 2 cars. My experience has been that if you have a .490 lift cam with a 113-118 overlap and about 280 duration, most of your power won't come in until about 2800-3200 rpm. In which case, a 2275 rpm stall will not put you into the proper power band to launch really hard.<BR>I ran an old KB118 cam in my 455 that was a slug until it went over 3000. Then it picked up the front end and pulled hard.<BR>A Schneider 290H cam had a bit more low end but still liked to be launched at 3000.<BR>There is a lot more on this too, and I will answer any questions you have. Please feel free to email me direct at the above address.<BR>Good Luck,<BR>Mark

[Guest grisby]

DCM422,Riv1973, sorry to interject on your posts, but I think were talking the same here. Mark, I have a 72 GS Stage1, BB trans etc, all stock except with the above mods. The Cam is a Torque tech "SP1S" with duration of 230/245 lift is 490 in and 501 exh and the lobe is 116 degree. My machine shop says that this is the same as the Lunati cam( I originally had a 288/96h TA cam in it but it was a defective grind and my machine shop replaced it with this one)( I had an earlier post in the year concerning the engine break in and tune up and the guys on the list helped alot-after all the tbl it ended up being a bad cam. Yes my shift points are around 5100, yes it does pull hard around 3000(I attribute that to the ATI torque converter. My total timing is 32deg all in by 2500, static timing is 12 deg, 800 cfm carb. BUT, before I put this torque converter in, with the stock converter I was able to really catch "gum" going thru the gears in Drive or manually. NOW it will only do it if I manually shift. If this is normal with this set up, fine, but its frustrating to read or hear stories on how the other owners of less modified vehicles are "burning" up the streets. From a dead stop in 1st gear I was able to lay down 87 feet of rubber(pardon my childish, old man grin) but if I would of or do start out with the car in Drive, it wont do this.<BR>Also,please pardon my ignorance, but when you say "launch" do you mean brake torqueing(hold brake to specified rpm and letting it rip)if so, I havent done that yet, then with this combo, then I should shoot out from the line like a bat out of he$$. Am I correct in that assumption. If so then I will have to give it a try.(bigger grin) But back to the original question as posted by Riv1973 and with my butt in follow up-then where does the kick down come into play or is it because of the "higher" stall converters that you dont notice it. I know of another guy(friend of mine in central NY) that is experiencing the same type of tbl that Riv1973 and myself are having and he has a lot more money in his engine than I do, but with basically the same setup-he has a TCI breakaway converter and his heads were professionally ported by another buick guru. Maybe I shouldn't say trouble, maybe its an adjustment? All I know is what I read on various groups, and you hear abt those guys smoking tires between gear changes etc etc, and like I said earlier, its frustrating with the time and money involved that I am not able to do that. But then again, are they?? <BR>Sorry for misspellings etc, its late and I am rambling, thanks again for you reply and future replies.<BR>bill g<p>[This message has been edited by grisby (edited 09-19-2000).]

[Guest]

Sounds like the only thing you guys need to do to your transmissions is some fine tuning.<P>The guys who say there burning rubber between shifts are full of sh## or running the original 70 series bias plys that came on their cars. Their probably getting a nice "chirp" that has evolved into "burning rubber"<P>But anyway, sounds like you both would have been happier with 3000 converters based on your engine combos. Or add a little more gear to get you in the power band of your cams a little faster.<P>Try this launch technique:<BR>Leave from an idle or just slightly above (say 1000-1500 max.). This will allow your Stall converter to flash to its maximum. The only problem will be wheel-spin of coarse, try to manage it best you can. Your best results will probably come from "stomping" to about half throttle then when the car is moving (NOT SPINNING) roll to full throttle.<BR>Spinning sounds/looks impressive but it doesn't do squat for foward motion.<BR>At the strip if you leave the line with a small "chirp" you just lost a 10th, thats about a CAR LENGTH at the end of a quarter, and that's NOT an exaggeration. <P>Keep testing and good luck!<BR>Dale

[Guest grisby]

DaleW, THANKS, that is what I figured,like I said,my car runs real strong. As for the launch technique-that I will definetly try- Like I was told a few years back--If you're spinning,you aint winning!!" DCM422, thanks for your insight on cams and offer to help at your private email--trust me I will probably take you up on that. Once again thanks and Riv1973, its your turn,-sorry to have to butt in on your thread.<BR>bill g

[Guest]

no appologies needed. i am very relieved to hear that i am not the only one with this delema. <P>i would love anyone to jump in and give advise and share insight. <P>so here is some further information about my cam and maybe this can help. <P>it is a 235/245 duration cam at 0.05. it has .501 lift for intake and exhsust. it has (i think. i am doing this from memory) 113 overlap. the carb is a 800 cfm q-jet that has been modified. it has 10.6:1 comp, 3.42 gears and headers and 2 1/2 exhaust, and a stinger ignition.<P>the torque converter is a 2275 stall (so i was told). do you think that this stall converter needs to be increased to a 2500 or 2800 stall? or does the gears need to be increased to 3.64-3.73 gears? or both. i have EXSTENSIVELY tuned this combo and i think that it is working good. there were some issues with vaccuum leaks and the motor rattling all of the bolts on the engine loose(mostly the header bolts and the carb bolts).<P>like i said before the car is a beast when launched from 2500-3000 rpm (and htat is by holding hte brake, revving the car and then dropping the hammer).<P>i know that burning rubber is not ideal for racing, but i only use it as a guage of power since there are no race tracks near me.<P>also with this combo, and insight on the vaccuum at idle and the max advance for the timing for this car would be? i just want ti make sure that i have things dialed in corretly (mine is 13-14 vac. at idle, which is 700-800 rpm, and 36 deg advance at 2500 rpm)<P>thanks a bunch. from riv1973 who is starting to find his way out of the woods.<P>

[Guest]

riv1973,<BR>Sounds to me like you do not have enough stall. The stock converter is only about 2200 on a Stage 1 trans. Dale is correct about launching. It is the "flash" that gets you going and braking it up to about 1000 should work fine. A good set of sticky tires will help you launch without spinning. I run a "switch pitch" that flashes to about 3200 and am only runnig a stock 70 455 Riviera motor. With M&H tires, it runs mid 13's with a 3.73 gear and headers.<BR>The low stall is about 2000.<BR>I am puzzled by it going better when you leave in L1 instead of Drive. Only 2 things are different in a th400 when in low. The low band is on which is only used in braking the trans and the pressure goes up from around 90 psi to about 125 psi in low.<BR>Gear ratio and function should be the same. <BR>UNLESS your trans is slipping and the extra pressure makes the forward clutch grab harder and send more drive to the axle.<BR>Another unlikely possibility is that the low roller sprag is partially slipping and that the low band is holding the reaction carrier and sending more drive out of the trans. I recently overhauled a trans that actually destroyed the low roller! I have been building th400's for over 25 years and it was the first time I had ever seen that, so I don't think it is your problem.<BR>The ATI should be a good converter. Also I think that TCI makes a good one too. It would also be helpful to know what trans shift kit you and grisby are using. I have not used one in years (I make my own) but recall that Art Carr made a good one that some Trans-Go kits were ok. <BR>A loose converter will also absorb a lot of shift firmness when driving easy, but should still kick it pretty good when you are on it.<BR>A lot comes into play with the type of valve body the trans has and how the rebuilder modified it.<BR>I hope this helps a bit.<BR>Best of luck,<BR>Mark

[Guest]

i have question. <P>from reading your note...can a loose converter cause a "worse launch" in plain drive as opposed to putting the tranny in L1 and launching?<P>also would a lock up converter cure this. and could i have a non lock up converter which is causing this poor drive gear launches?<P>my tranny and motor were put together by bill baylis. he has his trannies built by someone in Conn. (i think). he said that it was modified with the same number and style of clutches as a stage 1 tranny and then modfied for firm shifts.<P>but i think that it has a stage 1 stall converter, and from our chats, i may need a higher stall converter.<P>also how are the switch pitch converters and do you recommend them (also which company that sells them is the best to deal with?).<P>if you do not like them, what stall converter speed do you recommend?<P>also the tranny shifts out of 1st gear when the tranny is in drive really quickly as i drive around town. is this a problem for the tranny itself?<P>i am going to use it 90% time on the street, but i look forward to street races and drags when i am on the street. what is your recommendation as far as the way the tranny shifts and could this be related to a loose converter?<P>i really appreciate your help. i have no one to turn to about trannies and i hate to give the car to other people to diagnose these issues. they usually beat on the car, and i also can't learn if some one solves my probelm without educating me.<P>thanks and i look forward to your reply<P>