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Old 03-04-2019, 12:29 PM   #1
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Default Aftermarket rear sub-frame comparisons

After having recently finished an install of an earlier generation Kahplenke sub-frame, I was looking around for other things and stumbled across the one for sale at Retro-Turbo. I can't stress how shocked I was at how different it looked. Here are some pics....

Retro Turbo


Kahplenke


Who is running the top one? Any thoughts in this design?
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Old 03-04-2019, 01:05 PM   #2
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Christ, you wouldn't have thought they're for the same thing!
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Old 03-04-2019, 01:09 PM   #3
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.
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Old 03-04-2019, 01:39 PM   #4
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Looks like it ditches the sub frame and two torque rods and makes it just one torque rod. Seems like it might not keep the rear flat when it goes up and down like the stock setup. When the rear goes up and down compared to the car you want the pinion angle to stay the same, not sure this would do that. Looks like the pinion angle and the rear would twist up and down as it goes up and down.

But it might be long enough that it doesn't move that much and works just fine.
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Old 03-04-2019, 01:54 PM   #5
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One is solidly mounted and 1 has rubber bushings. So the Retro will transmit more NVH but keep alignment a bit better. I would go with triangles. You need solid mounting, rethink the whole rear end
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Old 03-04-2019, 02:29 PM   #6
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Originally Posted by sbabbs View Post
Looks like it ditches the sub frame and two torque rods and makes it just one torque rod.
Or perhaps you could say it it's an amalgam of the a sub-frame and torque rods?

The Retro Turbo unit does at least provide some adjustment to make sure the pinion angle can be set, but it looks like that entire assembly pivots up and down in the provided bushing. That means it controls movement up and down through a single pivot as opposed to the OE setup, which is multi-link and therefore has a virtual pivot center that I'm guessing is farther forward (while stationary) than what's used by the Retro Turbo assembly.

All that blathering done, I have to summarize and say that the Retro Turbo unit probably gets the job done, but it changes the kinematics of the rear suspension! If it's arrived at something better than what the Volvo engineers concocted, then right on! But I somehow am not sure they are aware of how they've changed things.

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One is solidly mounted and 1 has rubber bushings. So the Retro will transmit more NVH but keep alignment a bit better. I would go with triangles. You need solid mounting, rethink the whole rear end
Based on what I said above, I'm glad I have the Kahplenke unit.
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Old 03-04-2019, 03:28 PM   #7
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The MKM one is a bit of half arsed job. Functions but that is about as far as it goes. A lot of extra stress is being added to the bush at the front. It is probably fine for a drift car but for other uses not likely to be all that good
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Old 03-05-2019, 08:13 AM   #8
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The MKM one is a bit of half arsed job. Functions but that is about as far as it goes. A lot of extra stress is being added to the bush at the front. It is probably fine for a drift car but for other uses not likely to be all that good
Which one of the two is MKM? Thanks.



NVH?
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Old 03-05-2019, 10:19 AM   #9
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Originally Posted by Fred Gwynne View Post
Which one of the two is MKM? Thanks.
Top pic.

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NVH?
What about it? More or less? I'd say if you are really worried about that, stick with the original sub-frame but weld plates into like a lot of others have done, keep the OE rods and run rubber bushings.
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Old 03-05-2019, 12:45 PM   #10
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Originally Posted by Fred Gwynne View Post
Which one of the two is MKM? Thanks.



NVH?
NVH= noise, vibration and harshness
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Old 03-05-2019, 01:11 PM   #11
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I've personally never modified any suspension stuff on a 7/900, but I have had 4th gen F-body's, and the top bar looks a lot like the design of a 4th gen F-body. It probably works phenomenal, but as others have stated, it more than likely will transmit more noise into the vehicle. With that said, I would try the top styled bar without thinking twice if the vehicle was for performance use, it looks cheap, strong, and simple.
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Old 03-05-2019, 04:21 PM   #12
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As far as modifying the rear subframe, kerplunky just makes a stronger stock style rear sub frame. Myself, I just weld up the stock ones with more metal and then buy the kerplunky rods or I do have one set of IPD prototypes.











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Old 03-06-2019, 07:24 AM   #13
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Originally Posted by sbabbs View Post
As far as modifying the rear subframe, kerplunky just makes a stronger stock style rear sub frame. Myself, I just weld up the stock ones with more metal and then buy the kerplunky rods or I do have one set of IPD prototypes.

+12 to this, make your own and if you have issues then see about going someplace else for something better



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Old 03-06-2019, 10:23 AM   #14
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That (Retro Turbo) is not gonna keep pinion angle consistent when there is suspension travel.
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Old 03-06-2019, 01:42 PM   #15
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Also good to box in and weld up the part that goes into the dogbone like in this pic. That is the part where the stock subframe tends to bend and break. The weakest link.


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Old 03-06-2019, 04:51 PM   #16
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You know.... I was going to modify the OE sub-frame myself but the Kerp' unit popped up for sale for a pretty good price. That said, others that have done the install cut through the OE unit so they didn't have to remove the parking brake line. I'd imagine you guys modifying OE sub-frames are removing the parking brake line?

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That (Retro Turbo) is not gonna keep pinion angle consistent when there is suspension travel.
+1!
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Old 03-06-2019, 05:20 PM   #17
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We'll you can unbolt everything from the stock sub frame while it is on the car and wa-la, the two halves come apart. That way you don't have to unhook the e-brake line from the rear or the front to get it out of the center of the sub frame. Comprendo? IF your cutting up your sub frame to get it off without removing the brake line then your not thinking..


That being said if your welding up your stock sub frame and you want to put the ebrake cable back through the sub frame like stock after welding it up you will have to unhook the ebrake cable to do that. Or just run it on the outside of the sub, but mount it to it so it don't rub through.
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Old 03-06-2019, 10:15 PM   #18
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IF your cutting up your sub frame to get it off without removing the brake line then your not thinking..
Indeed I wasn't. I read what others said on how to do it.

But oh well... It's done.
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