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400i Rear Suspension Woes
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Posts: 4Registered: Dec 2014
Slowboot
Junior Member


Monday, January 26, 2015 6:20 AM

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Although there are a lot of folks who slam these hydraulic shocks, few have a concrete suggestion of what to do with them when they go bad. And they all do. According to what a Koni engineer told me,the bump stop material specified by Ferrari was incompatible with the ATF used at the time. It is exacerbated when the damper is left static for long period of time which frankly, is a common thing with all Ferraris. This causes deterioration of the fibrous material inside the shock and clogs up the various precision metering holes and check valves. Most OE shocks will be filled with decomposing bump stop material and this creates various functional problems such as no damping action or failure to hold pressure. Fortunately mine responded positively to a vigorous cleaning of debris but the damping action was non extant although they hold pressure very well.

So I was able to re-use two OE hydraulic shocks and two new QA1's. The OE shocks do not provide any appreciable damping but the QA1s are excellent at this. Also, the pump and actuator continue to function normally so I don't have to worry about burning out the engine-driven pump that is an integral component of the front accessory drive system. If I had to replace all four hydraulic shocks, I'd be inclined to plumb the hydraulic lines so that they formed a continuous loop and leave the pump, actuator and accumulators intact.

For road use, this combination of the two OE dampers and two QA1 coil-overs seems perfect although I am eager to test the suspension out when the weather clears up. Here is a photos of the completed installation:


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Posts: 9From: OrlandoRegistered: May 2003
400iGuy
Junior Member


Wednesday, January 28, 2015 1:51 PM

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Slowboot,

Can you provide specifics on the QA1 shocks you used?

Thanks,
Al

-------------------------
Al Cartlidge
Central Florida
407 341-2238 days


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Posts: 4Registered: Dec 2014
Slowboot
Junior Member


Friday, January 30, 2015 1:41 PM

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I used QA1 Model DS602 with "Stud-Top Adapters". These are described with dimensions etc. at Summit Racing. The Summit part numbers are HAL-DS602 and HAL-SS110SDM. I also used QA1 250 lb/inch coil springs, part number HAL-1GHT250. If you send me your email address, I can send you a compile set of instructions, photos and parts list. I don't think i can upload my Adobe pdf file to this forum.




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Posts: 9From: OrlandoRegistered: May 2003
400iGuy
Junior Member


Saturday, January 31, 2015 8:22 AM

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Thanks. That will be very helpful.
AWC_1934@yahoo.com


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Al Cartlidge
Central Florida
407 341-2238 days


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Posts: 1Registered: Oct 2015
Beamer
Junior Member


Friday, October 02, 2015 12:23 PM

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If you could send me the part list and instructions for changing to the QA1's that would be great. I looked briefly into the part numbers on the forum, but the spring number was not valid. Email- m.p.beam912@gmail.com




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Posts: 1Registered: May 2017
ocn
Junior Member


Thursday, May 11, 2017 7:58 PM

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Could you send me the details as well. oddcarnut@yahoo.com




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