5th to 4th Downshift...

[springerman55]

Now that my '83 SC is running again, I have an observation regarding the 5th to 4th downshift. Prior to getting the car running again, I had replaced the shift coupler bushings with the polyurethane version. The transmission shifts really good up and down in any gear except the 5th to 4th downshift. It is very hard to bring the shifter back to 4th gear from 5th without bumping/hitting (grinding) the reverse gear. Is my shifter adjustment that far off or is something else wrong that I missed? The car has not been driven much lately in the past two years due to me having surgery but I do not ever remember this being an issue (difficult 5th to 4th downshift). The reverse lockout spring/tension definitely works when the car is stopped. Does this lockout only work when the car is stopped/idling and not at higher engine/transmission rpms? Opinions???

[KTL]

The reverse lockout mechanism works when you pull straight back from 5th down to reverse. However if you go down and then over a bit toward 4th, the reverse lockout doesn't catch the shift lever the same way and you can touch reverse. I've done this with the racecar a few times!

When I want to get the 5th-4th downshift, I bring the shift lever to the neutral plane and then let the spring action (I have a Robotek mechanism that spring-centers the shift lever) place the shift lever in the 3rd-4th gate and then I drop it down into 4th.

[Peter Zimmermann]

When you nick R during a 5-4 downshift it is usually caused by the rotational adjustment being a tiny bit off. The problem can also be caused by the shifter not being at vertical in neutral. If your surgery recovery will allow, lift up the shifter boot so the bottom few inches of the lever (below the bend) are visible. Open both doors, kneel outside the car on the drivers side, and stick your head in under the steering wheel and forward of the seat, which should be all the way back.

Move the shift lever, watching the few inches below the bend, gently forward, then back, to the stops (don't engage a gear, work with the neutral stops), until you can visually find the middle of that fore/aft motion. Change your focus to something vertical (garage wall stud, telephone pole, etc.) and check your shifter (with the lever in the middle) against the vertical object you are using. If the lever is not vertical you must loosen the adjustment bolt at the tunnel rod/coupler, and move, lightly bump, the lever until it's vertical. Tighten the bolt and test drive.

If the problem still occurs (always downshift from 5 to 4 above 50-60 mph!), then you will have to engage second gear, loosen the tunnel rod/coupler bolt again, and change its rotational adjustment by a very small amount. This change sometimes happens automatically when you loosen the bolt, sometimes you have to move the lever a tiny amount. When you loosen the bolt do not lose your fore/aft adjustment. Trial and error will get your shifter to that perfect place.

[Flat Six]

Originally Posted by Peter Zimmermann

When you nick R during a 5-4 downshift it is usually caused by the rotational adjustment being a tiny bit off.

+1, Peter. Had exactly this issue w/my 915 (85 coupe). Two things to note:

1) Slight radial adjustment of coupling in tunnel behind the front seats was the remedy.

2) Also realize that the fore-aft adjustment may need finessing, too. If adjusted too 'short' for full shift into 5th gear (in my case I cheated a little on the full extension to 5th because I didn't want to reach as far), the shift lever may not extend far enough into the 5th gear plane to fully engage the reverse lockout. I readjusted fore-aft (less than 1/8" at the coupling), and -- shazam! -- no more nicking reverse on the 5-4 shift. And I didn't notice any additional "reach" at the shift knob.

Hope this helps.

Dale

[RWebb]

an easy test: bring the lever to N from 5th - wait a second... then put it in 4th

how well does that work for you?