|
|
|
|
| Author |
|
|
Registered
Join Date: Jul 2009
Posts: 25
|
Noisy 741 transmission
We have '63, 356, 741 transmission that is noisy only on acceleration. All bearings look good. I measured the back lash on the ring/pinion and it measured between 035 and 040. Ring gear states 015. Could this be why there is a noise upon acceleration?
Please also explain in layman's terms what the number means next to the back lash. Our number is -020. Thank you very much. |
||
07-27-2013, 09:34 AM
|
|
|
Registered
Join Date: Jan 2009
Location: maryland
Posts: 271
|
Two things control backlash:
(1) Depth of the pinion gear. Porsche publishes the nominal design value and they etch the deviation from that value on the face on the pinion. (2) After the depth has been set correctly, the backlash is set by varying the shim arragnment on the ring gear housing. The correct way is to measure the width of the housing with the new bearings in place, measure the ring gear housing width, find the difference and add .1mm for the preload value. Then divide this value in half and install the shims on the housing and measure the backlash. If it is not correct adjust with different sized shims on each side of housing (keeping the total amount of shim thicknesses the same) untill you obtain the correct backlash. As you can see it is a labor intensive process. Same process for the 911 gearboxes. |
||
|
07-27-2013, 01:41 PM
|
|
|
Registered
Join Date: Feb 2003
Location: Kailua, Bend, & Tamarack
Posts: 1,618
|
riedel, how did the backlash get so far out? Was previous work done on this transmission? Excessive backlash causes incorrect mesh. Incorrect mesh virtually always causes noise.
S1 and S2 shims may have been incorrectly flipped, or the pinion shimming may have been improperly increased. Bluing can be used to tediously arrive at correct mesh if you don't have the measuring tools. Even with the tools, bluing must still be used as the last step in confirming the correct setting. |
||
|
07-28-2013, 09:45 AM
|
|
|
Registered
Join Date: Mar 2003
Posts: 10,336
|
Check the gear oil level? Mine got "whiney" and it was very low. Need to put 90wt hypoid gear oil in it, but due to location of fill hole it is a real pain to do. Need a pump of some sort to do it.
__________________
“IN MY EXPERIENCE, SUSAN, WITHIN THEIR HEADS TOO MANY HUMANS SPEND A LOT OF TIME IN THE MIDDLE OF WARS THAT HAPPENED CENTURIES AGO.” |
||
|
07-29-2013, 05:06 AM
|
|
|
Registered
Join Date: Jul 2009
Posts: 25
|
Thank you all so very much for the information. With regard to Geary's question of how did the backlash get so far out. Yes, the transmission had previously been worked on and obviously not properly adjusted.
It is very much appreciated that you all took the time to respond to our question and all the info helped tremendously. |
||
|
07-30-2013, 07:35 AM
|
|
