Shift base bolts all broken

[svobrad]

Last year I replaced the stock shifter with the new Hurst retro-mod chrome stick with the white knob. Looked good but decided to put the stock set-up back in Sunday.
Each bolt head popped off! Was using a 3/8" drive socket with a stubby handle and thought I was being careful.
Did I not use the correct grade bolts or forget to put anti-seize on the bolts?
Had to find my drill and easy outs to remove the broken off bolts in the tailshaft. Took some time to do it - car was in the sun.
Took my time because I knew if I broke off an easy out in the bolt I'd really be in a jam.
Found 4 bolts from another transmission and used a lot of anti-seize and made sure I did not overtighten.
Have replaced lots of shifters over the years and this was first time a bolt sheared off (all four!). Used just a little sealer under the shift plate so know I didn't overstress the bolts the get a good seal.
Any ideas or similar experiences???

[svobrad]

Broken bolts

All four broke as I was removing them.

Guess they had been overtightened last year when I installed the new shifter.
I know better not to do so - this is why it came as a surprise.

I was thinking maybe there was a problem in the transmission tail shaft with overheating but no evidence or smell from that. Have seen where excessive overheating can seize a bolt.

[SVOeric]

one thing I can think of, your fancy retro-mod shifter was quite a bit taller than the stock one, allowing you a great more leverage than the stock setup. and if you get slammy with your shifts, I can see it breaking the heads off these bolts.

[gbeaird]

Eric, that's what I was thinking. Perhaps the bolts _weren't_ tight enough, and broke because the shifter was moving about too much during speed shifts.

Otherwise, you could have had them seize up if you didn't use any anti-seize of any kind, but even a little should help. Most aftermarket vendors don't use coated bolts, and some use bolts of questionable strength, so they may have corroded in place, and been too weak to hold coming out.

Was the removal of the remaining bolt shafts easy after you got the shifter out, or was it a PITA?

[svobrad]

The new shifter I installed last year was a Hurst shifter for '84 thru '86 Mustangs (even had the plastic console boot cover with Hurst on it) - had the chrome Hurst flat chrome shift handle. That reminded me of my old 1970 Mach 1 with the 351-C shaker hood engine & 4-speed.

Liked the original shifter better............

Took some time getting the bolt shafts out with easy outs. You have to take your time with those things!

Really don't think the thickness of the base was different though...........