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Replaced rear springs and shocks but.....


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Hello everyone,

    I just replaced my rear springs with moog #5379 and for shocks I used the Monro Sensa-tracs.  The car sits kinda low in the back now.  Im not sure I like it.  Could it just be the shocks are too soft/weak?  Im pretty sure the springs are factory replacement.  Any input is appreciated.  Thanks a lot!

 

Juan

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I am not sure but sounds to me like the springs area  bit soft. Normally shocks do not have a whole lot to do with the height of the car unless they are air shocks. I have been wrong many times before so if I am this time I will not be surprised at all.  

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Leghome,

    Thats why Im a little confused because they are the factory springs, and are brand new, but I always thought the monte sat even from front to back, if it were new, and mine seems to be sitting a little low in the back.

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Juan, you have a sharp looking Monte - nice color combo and wheels!  Are the photos in your Photobucket link before or after the rear spring replacement (I assume before)?  Did you take a reference measurement like rear bumper height off the ground before the swap?  I know from messing with my air shocks on my SS and Air Lift bags on my other Monte that the actual ride height can be very hard to determine by just looking or taking photos unless you have a good reference.

 

I generally look at where the top of the wheel well opening comes to on the wheel/tire.   Since the front and read wheel well openings are at different heights on our first gen Montes, it can appear that the rear is setting low because less wheel/tire is showing in the wheel well opening.

 

I just installed that same Moog spring in my SS and it definitely raised the rear relative to the front (which also had new Moog springs installed last year). You can easily see the difference in the before and after photos at the following LINK.  If you just want a higher static height in the rear, you can buy and install any number of spacers.  If you want height adjust-ability, I would recommend you look at an Air Lift 1000 kit instead of air shocks because they give the height without making the suspension so firm.

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Leghome, MCfan,

   I havent changed anything in the front at all, but I do have the springs and sensa-tracs for the front just havent gotten to them yet.  The pics on my photobucket page are a year or 2 old.  I had air shocks and different rear springs, I think variable rate, and the car hit hard, felt every bump, and not knowing if it was the fronts or backs, or shocks or springs that needed to be replaced, I figured Id just change everything to factory spec parts, thinking it would sit nice and ride nice.  I havent test drove it yet and wont judge the ride til I do the front springs and shocks.  I didnt take any measurements before I did the swap this past weekend.  I didnt realize it would change so much.  Kinda bummed.  MCfan, thanks for the compliment.

 

Juan

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I think those are the wrong springs. I have purchased 4 sets of new Moog rear springs over the years for the Montes I've owned and they always came up to the right height. I don't know the part number but just asked for MOOG OEM springs for the car at the parts store.

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If Moog #5379 and #6330 are "wrong" OEM replacements for rear and front coil springs of our first gen Montes, someone needs to tell Federal-Mogul, Summit and JEGS what the "right" replacements are because all three sources list exactly and only these springs.  #CC501 is a cargo carrier progressive rate spring for the rear, not an original replacement, although they may work great.

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GM used 10 different front springs in 1970 montes, and 3 different ones for the rear

 

and if you listen to the aftermarket vendors you will end up disappointed every time

 

and then you add how one person wants theirs to sit as compared to anothers

 

there is no real big block spring or small block spring, and if you check the part number of each from the vendor, 9 times out of 10 they are the same spring

 

 

front_springs

rear_springs

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That is great information to have, Sam, thanks for sharing!

 

The "Assembly Code" listed in the second column of each table can be found in Boxes 13 & 14 on the Build Sheet.  The following codes are listed on my two Build Sheets:

 

'70 402 manual: Front AO; Rear BM

'70 454SS auto: Front GQ; Rear BM

 

As expected, neither the Moog 5379 nor the Moog 6330 have technical specs that exactly match any of the factory springs listed in the two tables.  As shown below, the 5379 has a higher free spring height but a slightly lower deflection rate than any of the three rear factory springs.  The 6330 has a median free spring height but a higher deflection rate than any of the ten front factory springs.  These relationships will obviously yield different ride heights for different original spring combinations.

 

                                                          Moog 5379     GM "BM"         Moog 6330     GM "GQ"  GM "AO"

 

Bar diameter (in):                                      .56            .539                         .62           .621       .61

Deflection Rate (in/lb):                              122            130                         293           275        250

Free Height (in):                                    14.75         13.08                      17.50        18.13     18.29

 

If anyone wanted to closely duplicate their factory original springs, they would need to check their build sheet for the Assembly  Codes, get the specs from Sam's tables and then go looking for a spring from some manufacturer that comes closest to it.  Doubtful if any exact matches will be found unless there are still some NOS springs around that can be clearly identified by GM PN.

 

Going back to Juan's original post, I don't see how the Moog 5379 springs could make his Monte sit lower than the original spring, regardless of which of the three were used (they raised my SS nearly 2 inches).  I suspect the variable rate rear coils he replaced were taller than factory originals and possibly taller than the new Moogs, also.  Installing new springs on the front may even things out - only way to know is to try it and see.

 

post-567-0-31434000-1446661155_thumb.jpgpost-567-0-36676400-1446661227_thumb.jpg

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Thanks for all the info.  Im actually going to take the car out of the garage, and step back and take a good look at it.  Maybe Ill take a couple pics and post them, and you can all tell me what you think.  Again thanks for the info. 

 

One other question - are there supposed to be the rubber...I'll call them insulators on both ends of the spring; up in the spring pocket and on the axle where the spring sets?

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Insulators only on one end. I cannot remember it is the top or bottom. Top I think to help insulate the sound form the interior of the car. At least in my feeble mine that makes sense but my mind being feeble could spell trouble in a big way.

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Sam those pics in my photo bucket are a year or 2 old. I just did the rear springs and shocks this past weekend. I just measured from the rocker to the ground just behind the front tire and just in front of the back tire and the rear is up about 3/4 inch to an inch. So that's fine I suppose but I haven't done the fronts yet. Maybe I won't. Lol. I'll take pics tomorrow. It's already getting dark here in ny.

 

Juan

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Guys...some have mentioned that maybe things will even out once I do the front springs and shocks but wouldn't new springs and shocks just raise the front even more?

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Guys...some have mentioned that maybe things will even out once I do the front springs and shocks but wouldn't new springs and shocks just raise the front even more?

 

Not necessarily, Juan.  It depends entirely on how your new springs compare to those you currently have installed and if you already have any spacers in your front springs.  If the free height of the new spring is less than your current springs and/or the deflection rate is less, the weight of the front end of your Monte (which is constant) could result in a lower static ride height.

 

Unless you know for sure what you currently have installed (in terms of free height, deflection rate and possibly spacers), it would be almost impossible to predict how any new spring would affect the static height of the front end.  When I rebuilt the front of my SS two summers ago, I discovered that it not only already had Moog 6330 springs (stamped on each spring) but also had a 3/4" aluminum spacer ring between the lower control arm and the base of each spring.  I removed the spacers and the static height of the front end had to drop a bit (probably less than one inch) since the new springs I installed were also Moog 6330s.

 

Based on your photos and the more aggressive rear springs/shocks you discovered, I wouldn't be surprised if your current front springs are more aggressive than stock springs and/or you have some spacers somewhere in the assembly.  The only way to know for sure is to install the new springs and then be prepared to live with it or do it again if you don't like the results.  Even if you have a Build Sheet that tells which springs (see first table in Sam's post) your Monte was built with, that doesn't necessarily tell you what you currently have installed.

 

BTW, new front shocks (assuming they are OEM replacements) may change the dynamic (moving) feel of the ride or cornering a bit but should have very little effect, if any, on the static height of the front end.  Their primary function is to attenuate vertical motion throughout a range of travel, not change the height. 

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