Hi. New to this site but was told best place for advice. So I have a 1984 grand prix and switched from a chevy 350 to a pontiac 400 from a 70 grand prix. The trouble I'm having now is the drive shaft. I know u can shorten the shaft but I'm not sure if I'm measuring right. The shaft that came with the 400 is maybe 1 inch to long and I have a nice beefy one from a 69 grand prix that seems to fit but rear u joints r like 1/8 inch to big to fit in straps. Any suggestions would be great! And the transmission is a 400 turbo. Thanks
driveshaft from chevy 350 to pontiac 400
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I've never ran a TH-400, but have heard in the past that a drive shaft from a gbody with a 2004r will work with a 400 trans.
If any of your local parts stores carry Precision brand u-joints they make "adapter" joints that will marry two different series to each other. Just measure each that you need and figure out what two series that you need. Summit has them also and lists the sizes on their web site.
The 2004R takes the same driveshaft as a TH 350, not a TH 400, different yoke and length. You may be able to find a conversion U joint for the shaft that fits.
You should be able to use the 69 GP shaft but it needs to be cut 1" inch. You can use the same yolk from the 69 GP for the TH400, I've done it but it did have to be cut and balanced. I'm not sure what rear you have but you need the pinion yolk for the rear end off of the 69 GP as well.
84gp455....I have 342 with stock 10 bolt posi....the 69 driveshaft I have is length I need it's the rear u joints caps that r about 1/8 to big to slide all the way in differential....any ideas or did u run in to same thing and was fine? And I'm trying to see and look up universal caps but no luck yet.
I don't remember if I had to get a new differential yoke for it or not. Whats the u-joint part from the 69 GP? The c-clips should go on the inside of the caps. You may have to get the Grand National u-joints that's what I used.84grandprix said:
Yes they r the 69 joints. ...I also think I saw someone post about grand national joints...the original stock caps fits from the 84 on to the 69 and if I put them on the 69 I have just a little wiggle will that matter?..or do I need them tight? ...or when I put clamp on it will it run just as same?
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