M body- is it a handling nightmare

Chassis, Suspension and wheels

  1. CM360

    CM360 Well-Known Member

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    So I just picked up a '81 Diplomate with 42K, 2door,/6 1V, Black with tan interior,PW,PS,PB,A/C. It sat since '97 in a heated garage, no rust. What can I do to improve the handling? Heard all kinds of horror stories about tire wear and handling. My Dad's '77 Volare had all of that. I will replace the entire front suspension. Any parts that I can order to make it handle? Thanks
     
  2. kkritsilas

    kkritsilas Well-Known Member

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    The problems your dad's car had were probably due to the first year plus of Volare/Aspen production using a substandard K frame that bent over time. It bent to the extent that wheel alignment could not bring it back into spec. Consensus seems to be that the metal that the K frame was built with was too thin. There was a recall, and the thickness of the K frame was increased to the point that the issue went away. However, that original problem did a lot of damage to the Volare/Aspen quality reputation that lingered on for a while.

    Your Diplomat should not have this problem. It is built with the correct thickness K member. While there are certain aspects of the transverse torsion bar front suspension that are not ideal, the front suspension is not worse than the front suspension of other similar cars of that time period, as long as all the parts are in good order and the wheels are aligned to factory specs. It is not, by any means "a handling nightmare", and the geometry shortcomings, while there, only show up in extreme driving situations, which should not be performed on the street. If you plan on road racing your car, I would suggest that you find something else; other than that, it will be as good as can be expected from an early 1980s car. Firm Feel, a suspension specialist company, makes a vast array of parts that can make our cars handle even better, from sway bar upgrades to steering boxes, pitman and idler arms, and the list goes on, and includes the all important solid aluminum K member body mounts. Also, keep in mind that you car is 34 years old, and many of the rubber bushings, boots, and isolators are well past their best before date, so even just replacing them with factory spec. rubber part will make for a significant improvelment.

    Firm Feel is at www.firmfeel.com.

    This is just one example of what is out there. There are other companies (like Borgeson) who make a variety of parts that can work on our cars as well.
     
  3. Captain Caravelle

    Captain Caravelle Moderator--Mopar Maniac

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    Couldn't say it any better than that.
     
  4. Captain Caravelle

    Captain Caravelle Moderator--Mopar Maniac

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    Only thing I will add is that my 87 Fifth has been my daily driver for almost five years. Except for shocks the suspension is all stock.....handles just fine.

    It's not ready for auto cross but for regular driving I have no complaints......

    Post some pics of your new ride.
    Those Dip two doors are becoming very rare.
     
  5. slant6billy

    slant6billy Well-Known Member

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    That's good info. 18 years since driving? You have to really be careful. do a full fluid change, brake fluid, power steering fluid, trans fluid, rearend gear oil, coolant, and of course engine oil. just straight up fluids, no cleaners /additives/ magic in a bottle. change the thermostat especially. Fuel system - care there as well, the float, lines, filter. GET A FIRE EXTINGUISHER! *I ride with 2 of them. It is a cheap way to keep your old ride from burning up.
     
  6. Captain Caravelle

    Captain Caravelle Moderator--Mopar Maniac

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    X2.....and then some.
    There's a very real chance that every rubber line in that car is about to crumble....if there's any gas in that tank and it's 18 years old, it could be approaching paint thinner status by now. I would very carefully inspect everything.
     
  7. Aspen500

    Aspen500 Well-Known Member

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    I would highly suggest a Firm Feel steering box. Aside from completely rebuilding the front suspension, the FF box (got a Stage 2) was the single biggest improvement to handling I made to my car by a long shot. Not cheap (think it was around $425 after core return?) but worth every penny.

    Replacing the stock rubber k-frame insulators with poly units is a good upgrade also. Probably wouldn't recommend solid ones on a car like you've got. Not necessary and the poly gives a little vibration isolation yet, without moving around.
     
  8. slant6billy

    slant6billy Well-Known Member

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    And the poly stuff is never going to wear out. So if you plan on keeping the car for a good while, it is worth the extra $$$. Just remember not mix and match between rubber and poly. Things start to wear and other weird things happen
     
  9. Bruceynz

    Bruceynz Well-Known Member

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    Hi Everyone,

    Ok I want to clarify when you guys say "handling" do you mean driving down the interstate at 75mph or are you talking about throwing the car into hard corners around twisty roads?

    I would say my Cordoba handles like a dog, it doesn't hold a straight line at 60mph, in fact I would say it is scary. The steering box is slogged out as it has no bearings in it, I get underneath it and the rubbers are rotten, although the body mounts look ok. I have bought some FF upper control arms, FF alloy body mounts, Addco anti sway bars, have new torsion bar bushes and a heavy feel steering gear. I have already fitted new KYB shocks all round and lower profile tiles, I hope to be able to dial in my caster and get rid of excessive movement from rotten rubbers. It will be a while before I fit all this stuff, its all sitting in the USA at the moment waiting to be shipped out to NZ, when I have it all fitted I will put up a post on what I think the changes are like.
     
  10. Captain Caravelle

    Captain Caravelle Moderator--Mopar Maniac

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    Sounds like you might need to address a few things if it's scary at 60.....which it sounds like you're getting on top of.

    Like I said.... my Fifth is basically stock. I have done the balljoints but other than that and shocks it's bone stock.
    I grease all the fittings religiously and keep on top of maintenance.....I take that car 500 miles roundtrip to my trailer every weekend from May to October and it flies down the highway effortlessly. I'm normally doing around 70-75 mph and when I hit the sticks outside the city I've had her cruising at 90. Drives just fine.

    It is amazing what a difference there is when the front end grease reservoirs (balloons?) are filled as opposed to dry....it does get sloppy and wanders if they are not filled. But this is an old school ride and it's not going to drive like a new car.
    Cutting hard turns....yes it'll slop a little but I don't drive it like I'm trying to audition for fast and furious. I respect the car and drive it as such.....in return it gets me where I need to go in comfort. Let's be realistic...my Fifth is 28 years old and if I don't keep on top of things that are obviously going to wear out then I can't really expect it to perform 100%....
     
  11. slant6billy

    slant6billy Well-Known Member

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    If you can't hang on the highway without fear of 65 mph, there is some things you need to address. Is your Steering column or steering shaft in need of attention? With the car off how much steering wheel play do you have/ slop before the front wheels actually pitch left or right? The box is probably needing attention too. Don't just throw parts and money. Find a good shop. Steering links, tierod ends, the list goes on and can climb. So take it smart and slow.
     
  12. Bruceynz

    Bruceynz Well-Known Member

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    Hi Billy,

    I am not a mechanic, but have been around cars for a while, all you guys steering gear boxes with cars over 60,000miles are had it, Chrysler stopped putting bearings in the sector shafts (that's why they changed the size of the shafts in the 1970s, our cars have the large sector shafts) so the sector shaft pushes in the housing before it turns and adds play into the system. Another problem is the top A arms don't allow much caster, reason for this the more caster you dial in the harder the power steering gear has to work and wears the bearing less steering gear quicker, probably loads up the ball joint more as well but man they look pretty strong to me. The Max you can get is about 3 degrees if you are lucky and then that isn't even near what a modern car will have. FF let you dial in about 5 degrees which is good. But you will need a steering gear with bearings in the sector shaft to increase life of the steering gear. Those body mounts, mmmmm yes they let the front end move around like a dogs lips flap around when he has his head at the window at 65mph, they are there to stop the car transferring noise/vibration into the car but cause wander and vagueness and handling issue, the front wants to go one way and the back wants to go another. Another thing I noted with the transverse torsion bar set up is that there are no radius rods to hold the wheel in place, they rely on the torsion bar to do this, so you need to make sure those bushes are good as if they move the wheel moves back and forward changing god knows what, caster, camber and tow? I am no wheel alignment expert. So 30+ years of old rubber, Chrysler trying to make the ride plusher all add to cars that don't handle. These cars for everyday drivers, getting away for a Holiday and driving 1000 miles should do it nicely, I have driven modern cars that use Torsion bars and they go well so there is nothing fundamentally wrong with the torsion bar suspension, its not perfect not is anything else. I love it, its so simple and works well. A twisting rod is all it is!

    I guess what we have now is technology has moved on in 30+ years of FJM body cars, they were designed for different times, we are all getting old, I am over 40 now! But the thing is we can slowly work on these Gems and can get them to go not to bad at all!!

    Sharing information on here and what works is a great!!! I have had a lot of good advice on here!! I am no expert, anyone feel free to correct any mistakes.

    Thanks
    Bruce
     
    Last edited: Apr 12, 2015
  13. Aspen500

    Aspen500 Well-Known Member

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    Pay particular attention to the t-bar end mounts and especially the insulators at the frame mounting brackets. if they're slopped out the caster will be all over the place as the lower control arm can move fore and aft excessively.

    Just for info, I replaced literally every front end joint, bushing, etc during the build. Used stock replacement rubber bushings including the t-bar ends and mounting insulators. Had solid k-frame mounts but wanted a tad bit of noise/vibration isolation so I swapped them for poly ones. With the original (but rebuilt) steering gear it was about impossible to drive. Felt like the steering wheel was attached to the wheels with a rubber band. Took constant correction to go straight, curves were just as hairy. Added the FF stage 2 box (like I should have done from the start.......) and it drives/handles pretty darn good, even with that heavy 500" BB and A/C hanging over the front wheels. Should mention, rear has new springs with poly iso-mounts and round spring eyes (rubber bushings). Does it handle like even the average new car? No, but it handles 1000% better now than when I bought it back in '87 with 72,000 miles (suspension not worn out). What I mean is, once you rebuild it even with OEM style rubber bushings, it makes a HUGE difference right away.

    Actually, my opinion is once the k-frame is located decent so it doesn't mush around and the late '70's cheapo steering gear is replaced with a good one even if the other parts aren't totally like new an FMJ will handle a ton better.

    One other thing that contributes to better handling. I made front subframe rails to weld over the stock ones (similar to those rust repair caps) and fully welded the inner fender panels to them also. Mine originally had maybe 4 spot welds per side holding the inners to the subframe rails. Then, where the fenders mount I made 1x2 box tubing that basically frames the engine compartment (not visible with the car assembled), with reinforcing plates on the backside of the cowl. All this stiffened the front structure up and since the steering and suspension mount to it, improved the handling. Added bonus is the fenders don't jiggle around like they used to. Also added subframe connectors. Not just for the obvious reason but they also add torsional stiffness to the chassis which equals better handling.
     
  14. kkritsilas

    kkritsilas Well-Known Member

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    If the front end in in good repair, anything less than racing on a track will not show any limitations of the front end. Even hard cornering is fine. It may not have the steering feel of a modern car, but no cars from the 1980s did, including Corvettes of that era. However, if you were to change/verify all the bushings, ball joints, and tie rod ends, made sure that the car has a proper alignment, good tires, and the better body mounts (i.e. not 35 year old rubber), for street driving, the car will handle just fine. As for the caster available with the factory upper control arms, the 3 degrees available is also par for the course for cars built in the 1980s, from any American manufacturer. Caster has increased in more modern cars, so if that is what you are after, have a talk with Firm Feel.

    It must be kept in mind what these cars are, and are not. As I have written, these were not intended to be high performance sports cars. Even within the duration of their manufacturing run, the only car that may, and I stress the word may, have had any pretension to being a high performance car would have been the Cordoba LS/Mirada CMX, and they were only slightly oriented towards performance, and that was only in their first year or two. However, their competition, say the Monte Carlo and the Thunderbird for the J bodies of the same production year, or the Chevelle/Granada of the same years for the M body, were certainly not great handling cars, either, and I honestly believe that the J and Ms of those years were slightly better handling than their competitors. The fact that they can't handle as well as a modern car is more of things changing over time vs. a bad design. Newer suspenion designs have come along, and handling has more of an emphasis now than it did when our cars were in production. Back then, all of the manufacturers were looking for that mythical "Big Car Ride", and tuned their suspensions that way.

    If in good shape, I don't see why any of our cars would be found lacking, if it is kept in mind the way they were originally designed.

    The radius rod deletion, and the camber limitations actually created a controversy within Chrysler, and some of the suspension engineers even quit over it. But the transverse torsion bar suspension was used in millions of cars, and aside from the first year or so of substandard K members, has proven to be a good design. It was good enough to be used in hundreds of thousands of police cars for many years. It is NOT a sports car suspension; it was never designed to be one. It is a good, solid design for a street driven car, which is what it was designed to be.
     
  15. Bruceynz

    Bruceynz Well-Known Member

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    kkritsilas - I agree, I don't even think many people take their modern cars suspension to the limit in everyday driving, to many people say their car handles so well then I question them and time and time again when I have asked people about the handling of the car they actually mean it takes off fast lol lol not even close to what I consider handling is.
     
  16. slant6billy

    slant6billy Well-Known Member

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    My 76 was sloppy as hell. The 79 currently has a box out of the 85 AHB. My dads 83 Fifth was not as sloppy as the 76, but not nearly as tight as the AHB. My next box will be a FF stage 2
     
  17. Bruceynz

    Bruceynz Well-Known Member

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    Hi Guys,

    In NZ I have had my box machined with ford bearings fitted in the sector shaft and doubled up the reaction springs, I had 2 steering gears and I got the place to pull both apart and build me a super tight box, they managed to get the balls nice and tight in the nut! Sitting on the bench I now turn the input shaft and there is a slightest amount of play before it turns the sector shaft where is my current box has about an inch at the wheel this one I hope will be down to 1/8inch at the wheel which would be close to rack and pinon steering. The rack in my Subaru that has done 30,000miles has a small amount of play in it, you just can't get rid of it all :)

    I will let you know what I think when I put it in, I suspect this is what FF do to their boxes.

    BTW - the steering gear has more play the further you turn it off center, they are set up for straight ahead and that's where most of of driving is done, why I mention it is you should always make sure the wheels are in the straight ahead position when checking for play.
     
  18. kkritsilas

    kkritsilas Well-Known Member

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    My own criteria for handling is based on my 1993 Lincoln Mark VIII, and my current 2006 Monte Carlo SS (daily driver). While neither are all out sports cars by any means, both of them handle well. What I mean with that is that their reaction to turning the wheel is/was instantaneous, they didn't take much wheel movement to turn quickly, they are/were good at keeping a line even when taking a corner at higher speed, and the wheels seem to turn proportionately to the amount of steering input. As well, they were/are both good at communicating what the wheels are doing, whether it be in a bump or roughness of the road surface, as well as letting me know how hard I am working the suspension. Also, the power steering is not over boosted to the extent that I need to concentrate so much on steering that it detracts from keeping an eye on traffic and the road ahead.

    Some of that may be due to the high performance tires I am/was using; Lincoln used 225/60R16s in the winter, and 255/45YR17s in the summer ( a +1 fitment). The Monte Carlo SS is on 235/50R18s. Changing the Lincoln over from the winters to summers made a significant improvement in handling, more than likely due to less sidewall flex. The Monte Carlos SS handles as well as the Lincoln did, but is a front wheel drive car.

    Kostas
     
    Last edited: Apr 14, 2015
  19. Bruceynz

    Bruceynz Well-Known Member

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    Hi,

    I consider handling the ability for the car to hold the road when pushed into a corner, also straight line stability, It will be interesting to see how much improvements will be made when I have all my mods done.

    See You
    Bruce
     
  20. Captain Caravelle

    Captain Caravelle Moderator--Mopar Maniac

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    To me this is an excellent analogy of what the handling of a car is and my cars pass these tests. They most certainly do not drive like a new car but they communicate more than sufficient information to me about what's going on. Given the fact that I've been driving this era of car for a very long time I may be more used to it than somebody younger who is not. Straight line, cornering and overall driveability.....i have no issue whatsoever with these cars. Can they be improved upon? Sure.....but the foundation is there and in my opinion a very good one. Hopefully the OP is getting some good info from this.