Will i break it?

rjay455

Member
I have a 67 gs400 ,matching numbers 400, St 400 and 10bolt 2.93 gears considering fitting stage 1 455 from 71 rib with small cam a little head porting 10.1 piston 800 quad and hei dizzy, maybe 425 horse probably less, how will the stock tyranny ,( with stock rebuild ,as it has never been touched ), and the 10 Bolt feel about these changes? Are the up to the task?
 
You may be closer to 500 hp then 400 depending on the level of porting, cam and exhaust. The ST400 is very strong, and you should not have to worry about it unless the internal components are very worn. The 10 bolt should be fine unless you bolt slicks to it at the track. Then you might want to look for a 12 bolt with a slightly higher gear ratio.
 
Thank you Dr , for your reply, confirming what I was thinking ,I had read somewhere that the th400 was good for around 450 ftlb just thought I needed a second opinion
 
That 400 can take anything you throw at it. They are very tough transmissions. Ditto for the rear. Traction will put more stress on it, but the BOP 8.2 has bolt in axles, and is a sturdy rear. Even if you did break it, parts for that rear are readily available anywhere.
 
All 8.2s were not the same in strength. Larry's 70 was top of the line. Yours from 67 was not, but was still pretty tough. Below is an article from the GSCA on their variations and strength over time. I did manage to destroy a 66 3.23 posi rear from from a Buick station wagon (shared rears with GS in the early years) with repeated and constant abuse outside the track.
 

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The important thing to remember is that new aftermarket parts are available for the early BOP 8.2 10 bolt rear, gears, posi units, etc. Not so for the 68-70 Buick only 8.2 10 bolt. There are NO new gear sets available for the 68-70 rears. You can get Posi carriers, but they are more expensive. Last I heard, Fabcraft was planning another run of 3.42 and 3.64 gear sets, but that may be delayed now. That's it though. Should you break an early BOP rear, it can be repaired with readily available parts that are stronger.
 
Additionally, neutral drops are stupid and unnecessary. Even if your friends think they are funny, they are only funny until you are being towed home!
 
Initial OP question: Will I break it? It is a clearly related "if, then."
With the 455 he described, I would expect traction to be a problem if it is running correctly. Wheel spin won't break any thing unless it is suddenly and abruptly hooked up. That's unlikely on the street, and a maybe at the track. I still wouldn't worry about it on Drag Radials.

Neutral Drops though, LOL, yeah that's willfully trying to break it or bend the linkages. When I was a kid, I had a friend who did neutral drops with a Vega:D He probably bent the shift linkage on that car a half dozen times, and it was a company car with the stock 4 banger. It's a memory that never fails to make me laugh.
 
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