I have a 1972 GS 455/400 trans with a 1971 Olds 442 8.5 10 bolt 342 posi. I recently picked up a 1969 Chevelle 12 bolt that is beefed up with 4:11 gears, moser axles and bearings, south side bars,etc.. This rearend was setup in a GS with a 350 turbo transmission. I also got the driveshaft from this vehicle. I am wanting to just throw the 12 bolt in it for a couple weeks. Maybe run it at the track just to see the difference it makes in ETs over my 342 gear. Dont have any plans to keep 12 bolt in there, way too much rear end for my needs, just kinda wanting to try it before winter and before I sell the rearend. My Question is: What will I need to do driveshaft wise? From reading other postings about this, it sounds like the one in my car may be too short. The driveshaft I got with the rear end is the one I would prefer to use, it is a newer custom built aluminum/carbon fiber shaft with 1350's. It was built for the 12 bolt in a GS with 350 trans, so would it be the right length for this swap, if I just change to a 400 yoke or will this driveshaft be too long? Any help would be greatly appreciated! Thanks!
The THM350 can be about 3" shorter than a THM400. It depends on the extension housing on that THM350. Also, the 12 bolt uses a different rear u-joint.
Hey Doug,..just use your stock drive shaft you have now and call (joint, clutch & gear) in Romulus and tell them you need the offset u-joint for the 12-bolt...and buy the spicer u-joint, theres no zerk fittng in them ,.. there solid... They might ask for the measurement across the yoke on the 12- bolt and on the end of your drive shaft..which I think is 1350 and the 12-bolt yoke is smaller... I use the same u-joint for my stock drive shaft into my 12-bolt... Give me a call if you need anything... PS...Let me know when you want to sell the 12-bolt...when your done... jerrold,,
Hey Derek,.. I thouht that was you,.. lol...good to hear from you.. Billy drove it to a 11:57 at 115 +,with a stock driveshaft, 350 trans, and 3:73 12-bolt..
When I went from a Chevy 12 bolt to a Buick 8.5 10 bolt I had to shorten the drive shaft and change U-Joints. Bob H.
OK cool,its been a few years since that happened,good to hear from you too. I thought it was under the 11.5 rollbar threash hold,but 11.57 is pretty dam awesome to. I can't remember,did he win King of Street that night with your car? Was that back in 06,when I still had my 03 Mach1,or was that later?(Good times,it sucks getting old) Man,is Billy a great driver or what. I think his reaction time was a doule zero and 5 when he did that @ Milan Dragway. Have you taken your car to Milan lately? Or did your Daughter take it over from you?(LOL) Sorry DFMCQUICK,for highjacking your thread,but I think you got a couple of good answers. The only thing I would add is,keep the 12 bolt,and sell the other one.(it sounds like its not original anyway) You can always change the gear in the 12 bolt,get an overdrive transmission,or a gear vendors unit.
Derek, ...Billy used the car 2 yrs in a roll at King of Street and was runner up both times, that was in 06 and 07.... I took the car out last Oct. 2011 and it went 11:61 at 114.8 with 1.58 and 1.59 ,, 60 ft times... and drag radials.. I was happy with it,.. its still the same motor since 05',.. can't complain but she's getting tired.. I still drive it hard on the streets...lol... the car is willed to my daughter,... I'm now starting work on my sons 70' post skylark, Sorry about this Doug...
Sounds like she's still running strong,and this was what you called your "cheap" engine.LOL What is the plan for the 70',another 455,or a 350? Or something different? A Nail Head maybe?
Yep, cheap motor... - 70' car gonna play with the 350 Buick motor, it only has 78k miles, so will try ported heads , mild cam, t/a intake with 800 Holley, headers and 3" exh., 3:73 - 10- bolt and 3200 stall.. Prob. About 320 hp.. And no nailhead..lol..we do need to get off Doug's thread... PM me if you want to talk more.. Sorry again Doug ..
Tried to PM you,but your message area is full,it said you need to delete some of them if you want to get any more.
Thanks everyone for the input! Sounds like my original driveshaft with a special ujoint just might work! Now, I will see if I can get it done in the next week to make it to the local track before the season is over for the year. If not, I guess I will have all winter to figure out what I really want to do long term. Thanks again!
If you make it to Milan,let us know how it ran vs how the other one did. I think you're going to like the 4.11:1,if you can make it hook.:Brow:
Well, I never got around to doing the rear end swap before the end of the racing season. Wanted to just see how it would do, but didnt get the time to switch it. My long term plans are to go with 3:73 gears and I will probably just make the switch in my 10 bolt. We did make it out to Milan with the 3.42 in the car and ran a best of 12.72 at 107 mph which is the quickest it has ran. Car has had the same engine, trans, and rear end build for about 15 years. We have swapped tires, air cleaners, and that kinda stuff and depending on if I am driving or my son (75 pounds lighter) the car has been running 12.80s to 13.10s for the last 15 years. Just got into the 12.70s last time out with my son driving, 275/50/15 on the back and ran it with a 4" tall K&N Filter instead of its normal 3" tall K&N. High 40s temperature probably didnt hurt either!
