Topic: 6.9 suspension conversion

[john erbe]

 Purists read no further. However, in the event that someone is out there about to junk or sell his 6.9 too cheap because of endless suspension repairs and doesn't have a fat wallet -STOP! Just completed conversion, total cost about $900 in parts and that's with double adjustable coil overs in front. Had I used standards cost would be around $600. Instalation easy, and I'm just a shade tree mechanic with a floor jack and blocks. Put it this way, if I saw a 6.9 in junk yard with crapped out suspension and had all the parts in hand plus spring compressor for rears, I could drive car out in two hours and never have to worry about suspension again. Hopefully, this will keep more 6.9's on the road. If you want details send me a pm, glad to help.

[john erbe]

Michael:

I live in Vallejo, California. Yes, I have part numbers for the non-mercedes shocks and springs. Thinking about going one size smaller in front spring but first want upgrade the Bilstein/Mercedes spring set up in rear, see how it looks and then make decision. Will take some photos. Its real easy. Guy that told me about it just said he used coil overs in front, upper mercedes rubberized bracket off hydraulic strut, and had to machine brackets and a spacer. That was all the info I had to go on. Once I removed the upper bracket from from the 6.9's strut and laid it side by side a coil over shock with the "stud" mount on the top (and a few beers) Bingo! it came to me. Not knowing what the size springs, shocks or the rate of the spring, I had to do alot of running around. The machine work was easy. I didnt need a spacer, so his set up is probably a little different. Ironically, and here's the kicker, the front conversion is easier than the back.

[john erbe]

Just took pic's will send tomorrow. If any questions, just get back. Based on just a couple of test drives I would summarize accordingly: the old hydraulic had a smoother ride in that you did not feel the road and all the little bumps however in the dips you get that big gondola, riding the waves rebound and the excessive roll in the turns. The rebound and the roll are now history. You feel the road but I think going with a higher profile tire will help address that issue. Also, I took the easy way out and went with rear springs off of a junk yard 450sel, they're in all likelyhood, thirty years old. The 15" Yoko's currently mounted were a good match for the old system. I just need to fine tune the whole set-up. Best hing I ever did, no regrets. Now a new paint job and smaller repairs will be falling in place.

[oscar]

Hi John,

Wilst removing springs off a wrecking 280, your post came to mind.  Looking at the metal mounts that hold the upper rubber shims and the lower metal brackets for coil sprung w116's, it made me wonder what a 6.9 with only strut mounts needed has.  Are these metal mounts still there on 6.9's?  If not I'm still not sure how you achieved to seat the coils.  Can you elaborate?  Please

It sounds like an interesting conversion and although I've perhaps unfairly screwed my face up at 6.9's with coils appearing for sale in the past, you've got me thinking about the whole idea in a different light.  I suppose I'd want to have control over how the conversion was done rather than buying a 6.9 already done.

Another question - what about the hydro pump.  Did you just remove it and all the ancillaries then buy a blanking cap to cover the whole where the pump would go?  If so, did you have trouble getting the blanking plate?

[john erbe]

The rear is no problem in that the 6.9 has the upper spring perch. Shims and springs are available in different sizes and in different materials form other makers. I've ordered some shims from a company called energy suspension. The only diff. from the 4.5 is that the holes in the rear subframe for the bolts for the shock are not threaded but no big deal. I can tell you how I did mine if interested. Regarding front, you dont need the spring perch in that you are simply replacing the hydraulic strut with an adjustable coilover shock which fits in the exact same location using the rubberized top bracket on the 6.9 for attachment at the top. You will need a machinist to make the lower bracket for the lower attachment.

[john erbe]

Oscar: Regarding the blanking plate, some guys have used one from another model MB that apparently fits. In that I have a machinist that lives a few blocks away, I brought him an extra pump and he made a plate to match the pattern.

[oscar]

Thanks very much John.  I had to google what a coil over was would you believe but having done so and knowing what a McPherson strut looked like it all makes sense now.  Simple really, I should've known.

The only diff. from the 4.5 is that the holes in the rear subframe for the bolts for the shock are not threaded but no big deal. I can tell you how I did mine if interested.

No need really unless someone else wants to know.  It'll all be lost on me unfortunately without the real thing to go look at and compare so I wont push you.  All I got to look at is the subframe and axles from 280's and a 350 which I think are different from a regular 450 anyway.  It's an interesting mod and something I'll consider and revisit if I come across one that needs a suspension overhaul.

Re the blanking plate, true probably just about any 70's or 80's m110, m116 or m117 with a blanking plate will be interchangeable with the pump of a 6.9 and anything else that used the same pump and manufacturing a plate shouldn't be too difficult.  As long as it doesn't leak, all's good. 

[brandily]

John,
I just got a 6.9 last week, the car has not been used for a couple of years, I just got the car started, but it it sitting all the way down, I was beginning the think that I should do something else with the car, because it does need to be worked on, the problem is that in Mexico that kind of car was not sold here, , just a couple of imported ones, therefore it is very difficult to find replacement parts here, I would be very thankfull to have some of the pictures of that conversion.   

[john erbe]

Will send tomorrow.

[john erbe]

Brandily: Send me a PM and I'll send pics.

John

[ALV148]

The rear is no problem in that the 6.9 has the upper spring perch. Shims and springs are available in different sizes and in different materials form other makers. I've ordered some shims from a company called energy suspension. The only diff. from the 4.5 is that the holes in the rear subframe for the bolts for the shock are not threaded but no big deal. I can tell you how I did mine if interested. Regarding front, you dont need the spring perch in that you are simply replacing the hydraulic strut with an adjustable coilover shock which fits in the exact same location using the rubberized top bracket on the 6.9 for attachment at the top. You will need a machinist to make the lower bracket for the lower attachment.

John  what size and rate were the springs you used??

[rumb]

You are unlikely to get a reply as the previous posts are 12 years old and I dont think those members are around anymore.

[john erbe]

ALV148, still alive. Timely question as I just made a re-do of my conversion putting in shorter shock and softer spring. Rides much better. Installed a 10" by 450 lb. 2.5 ID Eibach. However, if I can locate a spring compressor I will go with the 12" spring. Dont like having to screw-up, if I remember, about 21/2 inches on shock.  Ride in fron is lower than standard which I prefer. Height from deck to center of wheel well is 24 3/4". I can give you info on shock if interested.

[ALV148]

Hi John thanks for the reply. I have use the inner wing turret Shock fitting point which has allow me to use a 12/19” coil over shocks which gives me more travel with a 13”  2.5” 425lb spring. But the spring is far to soft travelling 5” to rest. On my cals I need a 850lb to sit with 2.5” travel at rest. (1 inch lower than rear.  Any tech info would be great fully received. Thanks

[john erbe]

ALV...having trouble attaching photo. Send me a PM and Ill pass some along. I just installed the QA1DD403 which is single adjustable. My compressed height of shock, measured from center of bottom eyelet to top of spring is 11 3/8" with a compressed spring height of 6 1/8". Have about 2 1/2 " of thread showing on shock below bottom of adjustment washer. Approximately 12mm between coils, once again all this is at ride height/grounded. If you check the QA1 catalogue they've come out with a new advanced coil over, which is in the patent process but pricey. Mention because one of the size options would be more ideal, just slightly taller. My calc's showed a 500lb would also work fine.