420ponies Posted October 8, 2012 Share Posted October 8, 2012 I think I bottomed out my rear suspension.I went for a ride Sunday,last one for the year.I took it on a back road that I don't travel on and had my son, Nick (125lb) passenger in the back passenger side, along with my wife in the front.we were going along ,nice dip in the road, and WHAM! something hit hard on the frame I'm thinking.It felt like close to the trans? Got it home and looked underneath, nothing out of place.I have replaced the front springs last year,97,000 on the old ones.I'm thinking the rears need to be replaced.Also how much room should I have between the rear differential yoke and driveshaft when dropping drive shaft? I can just barely get the drive shaft out,maybe 1/2" clearence.Maybe this is what I felt.It was like the trans was coming up through the floor.We were going 60mph when I hit it.didn't see it 'til it was too late to brake.I'm going to get it up on stands and inspect it throughly today.I have solid engine mounts and a poly trans mount.I have rear air shocks,35psi in them when we left for the ride.Man, did it hit hard! Quote Link to comment Share on other sites More sharing options...
502ci Posted October 9, 2012 Share Posted October 9, 2012 I'm betting it was the driveshaft, should be fresh marks from the impact. Let us know what you see. Quote Link to comment Share on other sites More sharing options...
black07ss Posted October 9, 2012 Share Posted October 9, 2012 SLOW DOWN!! J/K hope there is nothing major wrong with the car now Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted October 9, 2012 Share Posted October 9, 2012 it should have hit the bump stops on the axle Quote Link to comment Share on other sites More sharing options...
MGD72Monte Posted October 9, 2012 Share Posted October 9, 2012 as well as the bump stop on the middle of read cross member. Look of a tell tale sign on the top of the differential housing. Â With those three bump stops, I'm thinking you should be OK. Quote Link to comment Share on other sites More sharing options...
Mikstudie Posted October 10, 2012 Share Posted October 10, 2012 Dump the air shocks and install air bags in the coils,fixed all my problems for 70 bucks...JMO!! Quote Link to comment Share on other sites More sharing options...
SS Haze Posted October 13, 2012 Share Posted October 13, 2012 I installed air bags 7 years ago. They work great. Â Mike Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted October 16, 2012 Share Posted October 16, 2012 Ya know I was thinking if the bump stops are gone maybe thats why it sounded real bad when bottoming out. Are they still there? did you replace them? Just a thought. Quote Link to comment Share on other sites More sharing options...
420ponies Posted October 17, 2012 Author Share Posted October 17, 2012 Hi Steve, No, they are new replacements.I have looked underneath,nothing.no signs of a hard hit, exhaust ok,it sounded more toward the tranny/tranny tunnel.I tried prying at the trans mount(poly)no movement,I'm still thinking my driveshaft is too long and when it bottomed out,the front yoke hit the trans output shaft? I can remember when I installed it,stands under rear axle,I had about a 1/2" clearence,maybe less, it was tight, to get the ujoint in the axle yoke(mine has the strap type yoke).I think that is too close.it should have about 1" clearence minimum.Also those springs are original to the car.I will be replacing these in the near future and try this road again to see the difference.I put it up for the winter and will be be working on it from time to time this winter.You know..... upgrades Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted October 18, 2012 Share Posted October 18, 2012 take out the rear springs and bottom out the suspension then see the there is any clearance left with the driveshaft Quote Link to comment Share on other sites More sharing options...
420ponies Posted October 18, 2012 Author Share Posted October 18, 2012 Hi Sam,Just what I was thinking on doing when I replace the springs.I do have a company not far from hear that will do a driveshaft for me if need be.I just never had this problem with a driveshaft before.You don't have a Moog part # for rear springs do ya? Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted October 18, 2012 Share Posted October 18, 2012 CC501 is what I used Jim they are the cargo coils give you a little extra unph if you ever need to load the trunk up but will give you stock height and good ride. Quote Link to comment Share on other sites More sharing options...
420ponies Posted October 19, 2012 Author Share Posted October 19, 2012 Hi Steve, looks like those are what everyone else is using .sounds good with me .I will order these from Napa. Stock height? I'm hoping I don't get anymore rake on the Monte.Remember I have cut coils on the front. 25 inches. from ground to wheel lip.about 1 1/2 inches front to back with 35psi in air shocks. Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted October 19, 2012 Share Posted October 19, 2012 They should work well for you, remember the new ones may be a little shorter than the old ones (unless there really bad) and the tighter coils go to the top, also order new insulators for the top unless you replaced them already. Quote Link to comment Share on other sites More sharing options...
420ponies Posted February 8, 2013 Author Share Posted February 8, 2013 To let everyone here know , I finally got around to checking this out.I have been getting my heat turned on in my garage(radiant floor) and aIso insulating the walls and ceiling.R49 in ceiling and R19 in the walls.I ordered the Moog cc501 coil springs( got those yesterday), jacked up the car ,unbolted the driveshaft,unbolted the shocks,lowered the rear axle,took the old springs out, jacked the rear axle back up to the pinion snubber,found the drive shaft hitting the floor crossbrace up near the transmission.That was the sound I heard!!The funny thing is no rub mark on the driveshaft in that area or any where else but I cannot get fingers around top of driveshaft.not even a piece of paper will slide over.This is with the axle hitting the pinion snubber.So, now I have the new springs in, I noticed in the box came special instructions to have the pigtail at the bottom of the spring to be parallel with the axle.I don't know if this makes any difference on how the spring reacts.The coils came out with little effort but I had a time getting the new ones over the spring locator on the axle,a little prying on the springs and jacking up one side of the axle was all it took.It is sitting only 1/2 " higher than before removing old springs(102,000 miles old).I think the old springs just bottomed out on that section of road.I will take down that same route this spring and see if it does it again.I just don't like it when cruising to have something like that happen. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 8, 2013 Share Posted February 8, 2013 maybe you should take a good look at your tranny mount Quote Link to comment Share on other sites More sharing options...
420ponies Posted February 8, 2013 Author Share Posted February 8, 2013 Hey Sam, I'm gonna take a look at this soon also,gotta get under the whole car and do some cleaning.I have a poly mount on it.I hope it is ok.The drive shaft has about 3/4" from the ujoint cap to the pinion yoke u-joint seat when the axle was up hitting the pinion snubber,so I don't think it effected the trans output shaft.Any thoughts if should replace this driveshaft with a shorter one? that is pretty close in my mind! Quote Link to comment Share on other sites More sharing options...
Leghome Posted February 8, 2013 Share Posted February 8, 2013 I had my drive shaft shortened by 1/2" when I had the motor out last year. It was very hard to get the drive shaft out of the yoke on the rear end plus every once in a while you could hear a slight banging sound when hitting harsh bumps. Since the shortening that sound has disappeared. Quote Link to comment Share on other sites More sharing options...
420ponies Posted February 9, 2013 Author Share Posted February 9, 2013 Hi larry,Yes that is my thought also.It should have 1 1/4" to 1 1/2" of move movement/slip. I think it could have damaged the tranny output shaft ,5/8" to 3/4" from end of u-joint cap to the seat of the pinion yoke is a little to close to me. The banging was the bottoming out of my suspension.it has a pinion snubber mark on top of the rear axle.this was at a speed of 70mph when it occurred last fall.I should think the driveshaft tunnel would not allow this but right near the cross brace on the floor board is where there is no clearance with axle up to the pinion snubber.I am still going to check the trans mount and see if it was damaged.looked ok but did not pry on it for movement. Quote Link to comment Share on other sites More sharing options...
Leghome Posted February 9, 2013 Share Posted February 9, 2013 The guy I bought my 72 from had a 700R4 installed about a year before I purchased it. It shifted very hard and I forget who on this forum told me check out BowTie Overdrives. I got one of their kits for the downshift cable and it made a world of difference. One of the best improvements I have done so far. Smooth shifting for normal driving and when I hammer it the tires bark when the tranny hits 2nd gear. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 9, 2013 Share Posted February 9, 2013 but if it's hitting the floor up by the trans...what's causing that? trans mount? worn out body mounts? something is letting the trans raise to hit the floor, also check your crossmember mounts too Quote Link to comment Share on other sites More sharing options...
footballubet Posted February 9, 2013 Share Posted February 9, 2013 Should not be hitting the floor. You definitely got a mount bad in that case. Quote Link to comment Share on other sites More sharing options...
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