In diagnosing the transmission noise I found that my 722.6, from a 1996 SL600, would make a clunking noise on start up and then under initial acceleration. Going under the car with a person starting it up on top I could definitely hear and feel the clunk was from internal in the transmission in the rear area. Considering that before this clunk started a week ago I did hear a very periodic once every 2 seconds rattle from the rear area, and that rattle is now gone the clunk is now present, I concluded rear sprag

My theory that the noise was coming from the rear F2 sprag. The sprag was engaging harshly on startup in park and slipping under load during initial acceleration. I felt that although the sprag has no real load during the start in park it will be capable of spinning and suddenly grabbing just from the clutch windage loads alone. During initial acceleration it slips and grabs.

I did a search on this sight and did come up with 3 threads indicating the early 722.6 had sprag failures.

In any case I'm going to pull the trans before any further driving. I have several questions.

1) Does this sound like a reasonably accurate diagnosis. I do have a 147 code.

2) I understand sprags and planetary bearings are week points. Are there updated parts for these.

3) Is it likely the sprag caused secondary damage to other nearby hard parts.

4) The VB is the original 1996 11/95 production date. This is the first VB and there have been several updates to both the VB and conductor plate. using a 1998+ VB will require a new computer. I am considering leaving this stuff as if can always be replaced later if need be. Is this risky???

Anything else I should know before going in.

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