915 Transmission Coupler Adjustment

[gopopracing]

'83 SC 915 Transmission fine tuning adjustment? Very familiar with the characteristics of the 915 transmission, having driven several over the years. I finished installing new clutch cable, horseshoe spring and rebuilding my pedal cluster. Have replaced all shift linkage bushings, etc. Adjusted the shift rod coupler per Bentley and other techniques offered by this site. I am able to shift into 1,2,3,4,5 and R smoothly with no issues. However, when shifting from 5th to 4th I nick Reverse ever so slightly. The lock out pawl is working as it should. I am theorizing that I need to shorten my shift rod ever so slightly (1mm) and double check that my shift lever is perfectly vertical. Any suggestions from the experts on this sight would be appreciated.

Thank you,

[MichaelSJackson]

While I'm no "expert", I have a procedure that leverages the difficulty of adjusting for reverse.

The short description is to start with the trans in reverse and the shifter in the reverse position. It seems you can get there? When in any shifter position, the shifter should/must have a little freedom to trace out a small rectangle. Otherwise the shifter will be pinned against one of the 4 sides. That's like constantly resting you hand on the sifter knob. (Not good.)

Coupler loose. (The collar nut; NOT the pin on the transmission rod.) Trans in reverse. Shifter past the lockout and in reverse position. Describe the small rectangle to yourself, then place the shifter in the middle of the rectangle. Tighten coupler.

Now shift to 1st. (Since that diagonal shift is the longest travel for the shifter, once that is adjusted, all the other positions will work fine.) Try to trace the rectangle in 1st. Is it floating in the middle and not pinned against any side? If so, you're done.

If it is pinned against a side, start over. Remembering which side it was pinned against, shift back to reverse and loosen coupler. Readjust the shifter position within the small rectangle, trying to eliminate the pinning in 1st. Just remember that the pivot in the shifter reverses the directions. (Pushing the shifter forward, moves the coupler back. Shifting left, rotates the coupler right. ETC.) Since you are already in reverse and the shifter is floating in the middle of the rectangle, you should only need very minor adjustments to correct the pinning in the 1st position.

(Remember you're only adjusting the shifter; not the transmission. The trans should be "clunked" in reverse.)

I hope this helps.

Michael J.
'78 SC

[gopopracing]

Excellent! Thank you for your great visual description and clear instructions.

[Discseven]

That sounds an interesting procedure Michael. Looking forward to have a go at that.

[JSV798]

Originally Posted by gopopracing

However, when shifting from 5th to 4th I nick Reverse ever so slightly. The lock out pawl is working as it should. I am theorizing that I need to shorten my shift rod ever so slightly (1mm) and double check that my shift lever is perfectly vertical. Any suggestions from the experts on this sight would be appreciated.

Thank you,

You need to lengthen it slightly: at the coupler loosen the bolt and pull the gear stick back GENTLY, no more than 1mm at the coupler. Best to mark present position with tape so that you can see how much you are moving it. DO NOT rotate coupler as your linkage sounds otherwise OK.

Roy

[gopopracing]

Thanks for the help. I reset the coupler and the transmission input. Indeed it was a very minor adjustment, no more than 1mm lengthening the shift rod. Transmission now shifts smoothly with no "nicking" reverse.

[JSV798]

Glad you got it sorted. Had the same problem myself so know what works. No point in starting from scratch when gear selection was otherwise OK. Just needed a bit of fine tuning.

Roy