July 2002
911 Throttle Linkage
Repair
By Steve Grosekemper
Recently, I was performing some extremely overdue service to my 911SC (you know what they say about the cobbler’s kids going without shoes). Before finishing up the service, I checked throttle, clutch and emergency brake linkage. When checking the throttle linkage, I noticed that the throttle was only opening about 75-80% of its capacity. Now, this may not seem like a big deal to some, but to me it was like finding a mystery $20 bill in my pocket (after it was fixed that is).
I knew I had full throttle the last time I had serviced the car, so some piece of linkage or a bushing must have worn out. The number one failure on these cars is the bushings that live in the engine and transmission bell cranks. This was the first thing I checked, but I found them to be in perfect condition.
The problem in this case, was not the bell crank bushings, but the bottom transmission bell crank and throttle rod. The main throttle rod from the pedal pulls the bell crank; which in turn pulls the upright throttle rod to the engine. The point where the bell crank pulls on the upper throttle rod gives us the greatest amount of wear, see figure 1 & 2.
Figure 1.
Worn Throttle Rod & Attachment Piece
Notice how the throttle rod and attachment piece are pulling through each
other and about to break.
Figure 2.
New Throttle Rod & Repair Piece
Notice full thickness of throttle rod and attachment piece.
The bell cranks are another story entirely. The various bell
cranks usually cost between $40 and $75, but can run as much as $150 for a
914-6! You have probably figured out by now that there is no way I would ever
spend $75 for a bell crank, let alone $150. You may also have figured out
that this article is going to tell you how to repair that pricey bell crank
for a substantially lesser amount. While thinking of a way to repair the bell
crank it all came to me. The bell cranks on ‘84 and later 911’s
have removable (i.e. replaceable) throttle rod attachment pieces. These pieces
can be attached to any transmission bell crank for a quick and easy repair.
This repair applies to all 356’s, 65-89 911’s, as well as 65-69
912’s and 914-6’s. The best part of this repair is the price. The
repair piece 911.423.227.00 costs $1.89 and the locking nut 900.910.010.09
costs 25 cents. No, that is not a misprint!
The repair process is as follows:
1. Replace the worn throttle rod as necessary
2. Remove the worn out transmission bell crank
3. Drill out back side of original throttle rod attachment piece, see figure
3.
Figure 3.
4. Drive out remaining attachment piece with a drift pin
5. Drill the existing hole to accommodate the larger 6mm hole of the repair
piece
6. Insert the repair piece and tighten down with the supplied locking nut
7. Re-install the bell crank and adjust the linkage as necessary to obtain
99% of throttle opening
Be careful while adjusting the throttle linkage. If the linkage is pulled
too tight and binds, you can create a whole new set of problems. These problems
can manifest into a bent pedal assembly bell crank, which can cause the throttle
to stick wide open (for a real E-Ticket ride!).
The key to getting the maximum life out of this repair is proper lubrication
at all of the critical wear points. I like to use Porsche high temperature
clutch grease, Part #000.043.024.00. It seems to last the longest, under the
most extreme of conditions, but certainly is not the only option. Plain white
lithium grease will work fine when reapplied at each service interval.
Good Luck!
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