107 Subframe update
 

I need to purchase a new subframe for my 1986 560SL. I know at one time the 107 subframes were updated for strength. Does anyone know when this occured. I prefer to get one that came updated from the factory rather than strengthend acording to the service campagian. So far I have located two subframes one from an 85 380SL and one from an 84 280SL Euro.

John Roncallo

Hi John,
I looked into this when I had to replace the broken subframe on my '82 380SL - Performance Products carries the subframe for around $650, and it might be available here on the forum also. I went to the local wrecking yard and got a subframe from a 114 chassis and installed the factory strengthing braces on it, which in my opinion aren't very substantial, and very spendy. (around $100) If you install the strengthing braces they MUST be MIG welded. My '79 has the improved subframe on it, and it is actually boxed in around the lower control arm tabs, a much stronger setup!
In my opinion, the newer boxed subframe is worth the money, and I should have gone with it. If you raise the front of the car up on blocks you can do the replacement job in around 4 hours. Be sure to have both new motor mounts and new subframe rubber on hand. It might also be a good idea to replace the sway bar rubber at the same time, since you have to disconnect the links.

My question is when were the newer subframes installed on the production cars. I have to purchase these sight unseen from the junk yards so if I get one from an 85 or 84 will it be the new style or the old style.

This subframe is to be modified for the installation of an M120 V12. I need the strongest solution I can get.

Thank You
John Roncallo

Hi John,
As far as I know, they NEVER were updated - when they started installing the aluminum V8's they stuck with the original subframe. If you want a strong boxed subframe you have to buy one from an aftermarket supplier. If I'm wrong on this, please correct me, but I've never seen a boxed subframe from the factory.

107 subframe
 

The strengthened subframe went into production use at the begin of production of 560SL (1986).
I've replaced many 107 subframes that had been retrofitted with gussets.
Mike

Thank you Mike. That is what I thought. Does that mean that the retrofitted frames failed either due to inferior workmanship in the field or was it an overall bandaid approach. Are the modified subframes exactly like the new units or do the new units have more than just two webbed pieces welded to the aft control arm mounts.

Thanks
John Roncallo