The DREADED 1st-to-reverse, Have developed a process that is straight forward to prevent the 1st to Rev Options

[ctc911ctc]

914-6 all original - rebuilt the transmission

This is part of the rebuild thread - http://www.914world.com/bbs2/index.php?sho...3371&st=100

Transmission - Shifter -> This is my working theory, I am probably wrong.... (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/dry.gif)

While I am chasing the 'carb-spitting' issue, I am also chasing the shifter being.....OFF

This is manifesting itself as the DREADED 1st to reverse problem.......As to the condition of the 901, gears are all within spec, new syncs 1st and second, new slider for 1st reverse - new dog teeth for 1st and second.

Let me explain,

When I put the car into 1st or reverse, I (as well all of you) push the lever from RIGHT to LEFT and feel the spring pressure of the shift plate.

About 1/4 of the way to the full extent of the spring compression the there is strong resistance. BUT i can CONTINUE to push to the left. I believe that I have reached the limit of the various linkage components and that what I am REALLY doing at this point is torquing the linkage. I can then continue to torque the linkage until I have reached the full travel of the shift lever spring plate



What happens is; when the shift comes out of 1st, there is no SPRING BUMP to push the selector in the transmission from the 1st-reverse position to the 2nd-3rd or middle position.

I have cut pictures from Clay Perrine's excellent 901 cut-away to depict what is happening

Transmission is in Neutral on the other side of the selector bars is a vertical channel, there is a knob that is in ONE of the THREE channels - when moved the selected bar moves left to right



Now, the knob is in the channel of the lowest bar AND the bar is slid to the left for FIRST GEAR



My shift LINKAGE - not the shift lever - when moved forward never gets the BUMP from the spring and as a result STAYS in the LOWEST position THOUGH the shift lever HAS moved to the right and you think that the shift is in the correct place BUT NO, it ends up pushing the SAME slider BACKWARD into reverse



OUCH!!!!!

What should happen is the selector should get a bump to the next position from the spring and end up here.




MY PLAN

I am going to adjust the Shift bar about 20 degrees to I do not get any mechanical loading, not sure if 20 degrees is correct......feels right.......

[ctc911ctc]

*******UPDATE***********

Did you ever have the feeling that you were making a situation 10X more complicated than necessary? Yea, that is what I am feeling now.

My sense of the transmission linkage is that the engineers in Germany added components to natively connect a 901 transmission to engines that have been 'turned around' where the back is not the front and the front is now the back.

In the early 1970 914s, either 6 or 4 this involved the following:

Hand to Shift Linkage transform
Lateral Adjustment transform - at the fire wall
90 degree transform - at the tail, changes rotations from Front/Back to Lateral
90 degree transform - inside the 901, changes lateral to Back/Front - end of 180 deg transform
Selector Transform - selector Rod to Gear-channel-Gear selection

Each of these transformations introduces 'lash'
In a new car this lash is within SPEC

**********End of Analysis**********

So, I wanted to make certain that when the spring plate was unloaded all of the transformations resulted in the gear selector (final stage in the transmission) was in the 2nd/3rd slot........

Sooo, I started by selecting Reverse and then getting the various components in the 1st/Rev position.


As the car gets older all of the soft components age and introduce more lash
In a small way all of the assembly components also introduce lash, roll-pins, U-Joint Bolt, etc.....





Now I unbolt the rod that attaches through the firewall and the nut is slipping......WHAT? I was a bit surprised - on my '74 this is not the case, the nut will stay in position........Soooooo

I had to fashion a tool to hold the nut, took a few hours of trail and error.



After the bolt was loosened, I then went and made sure that the gear-shift was in the position of Reverse, that the springs were fully loaded but not too much pressure.

This introduced about a 10-20 degree difference from where the rod entered the receiver as seen above.

Tightening this bolt was 10 times the pain as loosening, I will post a picture of the tool I fashioned to hold the nut asap.

Shifted better on the stands - not 1st to 2nd grind, but if may be going into 4th..... (IMG:style_emoticons/default/mad.gif)


Will test drive today.

More to come.