3800 M90 Montana Van

Mattstrike

Random Crazy Custom Car guy
Feb 13, 2014
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OK, going to go off the deep end here just a bit.

The Montana, rear shocks are the auto level shocks. There was only one option for replacements: softy mcsoft. The fronts are significantly stiffer, so when you go over a decent bump the rear feels like it's bouncing while the front end does not. The next part of the rear end suspension is that I need to get a bump stop in there that will prevent the rear wheels from encroaching into the rolled fenders. Of course, the factory bump stops are garbage to begin with and completely gone anyway (I found the remnants of one of them on the ground in the hole it sat for 10 years in, only just now put it together that's what it was).

Is there something I can put in the coil spring that would effectively act as additional damping as well as a bump stop? I don't want to give up the level control. I thought about doubling up the rear shocks with a random/universal monotube, since that angle they are on is crappy to begin with, but there's not a lot of room for that and the angles mean any integrated bump stop is going to probably bend metal things on the body. Bump stops are the easy part, I'd weld something on to the axle beam and unibody for that, it's the shock that I'm not sure how to handle.

lujGtFs.jpg
 

Bob Kazamakis

I’m the f-ing lizard king
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I mean none of those things are going to add dampening, just spring rate.

I’m not sure if the stock compressor could handle a set of adjustable air shocks like James suggested but that would probably get you more dampening but length might be an issue. Adding another shock if there’s room is what I’d try second. Plenty of universal mounting options out there.

 
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Turbocharged400sbc

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Is that the angle they are installed at or is the top unbolted in that picture? If that s*** is really at that high of an angle to the vertical travel of the axle their functioning at half of their actual dampening so if you move the stock to a more vertical position it would affect the dampening a lot better ( it equates to more leverage iirc) since it would be directly damping the vertical motion instead of at an angle
 
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Mattstrike

Random Crazy Custom Car guy
Feb 13, 2014
542
1,139
Yes, that really is the angle they mounted those shocks at. That's at ride height too. I'm going to see if I can fit a monotube just inside the existing ones with some really long bolts and spacers. I also discovered that they make an aftermarket heavy-duty spring set for the rear, I might try that as well.

I have a 3D model of the rear caliper bracket, I'll try to remember to share a dimensioned sketch of it.
 

Mattstrike

Random Crazy Custom Car guy
Feb 13, 2014
542
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When you go through the swap could you post a picture of the caliper, bracket and Pad shape?

A few images that might help. First, the 05+ U-platform factory bracket:
0AkPnWB.jpg


The wood template I made to verify my dimensions:
sDCtR6W.jpg


5LCP31I.jpg


Axle beam - old style has a spacer, the update for rear discs GM converted it to the flat bracket:
oSODHz3.jpg


Me trying to free-hand it like a boss:
HjnBmkn.jpg


If you need another view let me know, I'll grab it when I dig into it later.
 

Mattstrike

Random Crazy Custom Car guy
Feb 13, 2014
542
1,139
Wow. Were you drunk when you typed that out, or am I too drunk to read again?

Unless you're trying to AWD swap, there is no subframe. You could take the uplander/terrazza/sv6 axle beam if you could find one not rotted out or bent in the middle from some dumbass using a floor jack on it, but part of the reason I did it this way is I was looking for alternative rear disc brake setup options for my 92 SSE. Fun story: the uplander, terrazza, sv6 are the same van with different front bumpers and some minor sheet metal body lines. If I get bored one weekend I'm going to swap a 97-04 front end on one in the u-pull just to fuck with people.
 

Turbocharged400sbc

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is the 05+ rear having the shocks at the same steep angle as your older suspension. yes i know people swap the uplander stuff onto the back of bonnies/etc fore the newer rear brakes.

honestly i think the best option might be to extend the beam trailing arms towards the rear of the van and mount the bottom of the shock there, farther behind the axle centerline....that would greatly increase its leverage over the axle, and stand it more vertical also increasing its effective damping over the rear travel. and it could be as simple as notching some 2x2x1/4in sq tube....

adding another shock only works if thats the easier way.....
 

CMNTMXR57

GM, Holden & Chrysler Mini-Van nut swinger
Sep 12, 2008
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He does. It was in the background of Ryan's pic of his GTO hood the other day.


1694184585570.png
 
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