Body not sitting on chassis squarely

[C-Mack]

I noticed the left rear tire/wheel seems to protrude out from the fender a little more (about 1/2”) than the right rear tire when viewing down the side of the vehicle. The opposite seems to be the case at the front suggesting that when the body and chassis came together on the assembly line it was twisted slightly to the left at the front and slightly right on the rear if you were to view it from the top down. I assume there is some tolerance allowed when they bring these two giant assemblies together but is this an issue or can it be corrected? I believe there are eight rubber mounts holding the body onto the chassis. I wonder if they can be loosened and the body shifted slightly to align things better?

 

[Logsplitter]

I noticed the left rear tire/wheel seems to protrude out from the fender a little more (about 1/2”) than the right rear tire when viewing down the side of the vehicle. The opposite seems to be the case at the front suggesting that when the body and chassis came together on the assembly line it was twisted slightly to the left at the front and slightly right on the rear if you were to view it from the top down. I assume there is some tolerance allowed when they bring these two giant assemblies together but is this an issue or can it be corrected? I believe there are eight rubber mounts holding the body onto the chassis. I wonder if they can be loosened and the body shifted slightly to align things better?

If that is the case, I would be taking it straight back to the dealers for evaluation and maybe a second opinion of the issue.

 

[Tom D]

I’d be surprised if there’s half an inch of movement there! I would Imagine it’s a more precise fit than that. Could there be an issue with the axle linkage?

 

[C-Mack]

I’ve done some rough measurements from chassis to fixed points on the axles and they are the equal side to side so it’s not an issue of the axles being installed incorrectly or twisted. Also, the panhard rods hold the axles laterally and are not adjustable so the likely hood of them being out that much isn’t the issue. You can see the rear most body mounts under the back of the vehicle and they are slightly offset to the right hand side which is consistent with the body being placed slightly askew on the chassis.

It really has to be something as to how the two assemblies came together in the factory. Vehicle has 200 miles on it and has not been off-road yet so I doubt the body has moved on the chassis on its own. The mounts should be self locating/centering but I’m wondering if there is just enough play in the mounting assemblies when body came down from above on the production line they just didn’t give it a final tweak to make sure it was centered. It’s not glaringly obvious looking at the vehicle but just something you notice as you spend more time working around it. Doesn’t seem to present any drivability issues but it would be interesting to know if there is a tolerance for this on the production line and if there is anything that can be done to straighten it up at the dealer?

 

[AWo]

That could be normal!

Do you have a lift? If, that is normal. However, even if not, the axle is mounted to a radius arm, called Panhard rod to keep the axle where it should be, under the car. It takes all side forces. A Panhard rod means the axle moves on a radius. So if the axle moves up (or the chassis moves down) or vice versa that leads to the axle moving sideways. BTW, that is absolutely necessary for the front axle. If the front axle would not be able to move sideways your steering wheel would turn one or one and a half or more turns, when the axle moves up and down. That's the reason why the steering rod is mounted in the same direction as the Panhard rod. The steering rod is also a kind of link which creates a movement on a radius. If the axle would stay exactly in the middle, the mitigation would be done via the steering rod (pushing it) and thereby turning your steering wheel.

So each change in load and height and each relative movement of the chassis to the axle will lead to a side movement of the chassis (or the axle, depends how you look at it).



This side movement is because of its design and physics and its what makes this kind of suspension not good for rallyes. The Land Rover Discovery 2 had a Watts Mounting scheme on its rear axle, keeping it nice in the middle under the car what is good for fast driving on corrugated tracks and jumping,

Upper picture: spring deflected
Lowe picture: spring rebound


AWo

P.S.
You may want to translate these six small articles I wrote a few years ago about axles and their mountings via an AI engine into you language: https://matsch-und-piste.de/achskonzepte-bei-gelaendewagen-teil-1-starrachse-und-blattfeder/

 

[Jean Mercier]

That could be normal!

Do you have a lift? If, that is normal. However, even if not, the axle is mounted to a radius arm, called Panhard rod to keep the axle where it should be, under the car. It takes all side forces. A Panhard rod means the axle moves on a radius. So if the axle moves up (or the chassis moves down) or vice versa that leads to the axle moving sideways. BTW, that is absolutely necessary for the front axle. If the front axle would not be able to move sideways your steering wheel would turn one or one and a half or more turns, when the axle moves up and down. That's the reason why the steering rod is mounted in the same direction as the Panhard rod. The steering rod is also a kind of link which creates a movement on a radius. If the axle would stay exactly in the middle, the mitigation would be done via the steering rod (pushing it) and thereby turning your steering wheel.

So each change in load and height and each relative movement of the chassis to the axle will lead to a side movement of the chassis (or the axle, depends how you look at it).

View attachment 7869698

This side movement is because of its design and physics and its what makes this kind of suspension not good for rallyes. The Land Rover Discovery 2 had a Watts Mounting scheme on its rear axle, keeping it nice in the middle under the car what is good for fast driving on corrugated tracks and jumping,

Upper picture: spring deflected
Lowe picture: spring rebound
View attachment 7869700

AWo

P.S.
You may want to translate these six small articles I wrote a few years ago about axles and their mountings via an AI engine into you language: https://matsch-und-piste.de/achskonzepte-bei-gelaendewagen-teil-1-starrachse-und-blattfeder/

Your knowledge and help on this forum is impressive! Thanks for that

 

[C-Mack]

That could be normal!

Do you have a lift? If, that is normal. However, even if not, the axle is mounted to a radius arm, called Panhard rod to keep the axle where it should be, under the car. It takes all side forces. A Panhard rod means the axle moves on a radius. So if the axle moves up (or the chassis moves down) or vice versa that leads to the axle moving sideways. BTW, that is absolutely necessary for the front axle. If the front axle would not be able to move sideways your steering wheel would turn one or one and a half or more turns, when the axle moves up and down. That's the reason why the steering rod is mounted in the same direction as the Panhard rod. The steering rod is also a kind of link which creates a movement on a radius. If the axle would stay exactly in the middle, the mitigation would be done via the steering rod (pushing it) and thereby turning your steering wheel.

So each change in load and height and each relative movement of the chassis to the axle will lead to a side movement of the chassis (or the axle, depends how you look at it).

View attachment 7869698

This side movement is because of its design and physics and its what makes this kind of suspension not good for rallyes. The Land Rover Discovery 2 had a Watts Mounting scheme on its rear axle, keeping it nice in the middle under the car what is good for fast driving on corrugated tracks and jumping,

Upper picture: spring deflected
Lowe picture: spring rebound
View attachment 7869700

AWo

P.S.
You may want to translate these six small articles I wrote a few years ago about axles and their mountings via an AI engine into you language: https://matsch-und-piste.de/achskonzepte-bei-gelaendewagen-teil-1-starrachse-und-blattfeder/

I appreciate the insights and totally understand how the suspension works and the geometry change with height due to the fixed panhard rods as your explanation was helpful. This is a bone stock Fieldmaster on factory Eibach springs. This is how it came from the factory. Another spot you can see the difference at the rear is the spacing between the right rear bumper cap and body as compared to the left rear. On the left rear there is a 3/4” gap where you can fully get your fingers in (yes not scientific I know) but on the right rear the gap is only about 1/4” or so and you can’t get your fingers in. The entire bumper is mounted to chassis hard points so where I’m seeing the left rear wheel stick out a bit more there is the wider gap which suggests the entire cab is sitting at a crab angle toward the right hand rear where the gap is only a 1/4”. If this is within manufacturing tolerance for when they mated the cab and chassis in the factory so be it, but I would agree with others in that you would think the cab/chassis alignment would be a bit more precise? Problem is now that I know it’s off I can’t unsee it when I look at the vehicle. Seems like a small gripe yes, but still annoying.

 

[trobex]

I appreciate the insights and totally understand how the suspension works and the geometry change with height due to the fixed panhard rods as your explanation was helpful. This is a bone stock Fieldmaster on factory Eibach springs. This is how it came from the factory. Another spot you can see the difference at the rear is the spacing between the right rear bumper cap and body as compared to the left rear. On the left rear there is a 3/4” gap where you can fully get your fingers in (yes not scientific I know) but on the right rear the gap is only about 1/4” or so and you can’t get your fingers in. The entire bumper is mounted to chassis hard points so where I’m seeing the left rear wheel stick out a bit more there is the wider gap which suggests the entire cab is sitting at a crab angle toward the right hand rear where the gap is only a 1/4”. If this is within manufacturing tolerance for when they mated the cab and chassis in the factory so be it, but I would agree with others in that you would think the cab/chassis alignment would be a bit more precise? Problem is now that I know it’s off I can’t unsee it when I look at the vehicle. Seems like a small gripe yes, but still annoying.

Seems odd others here have not noticed which leads to you issue being a possible production line fault? Hard to say - I would lodge it as a defect see if dealer can rectify or identify etc etc.

 

[C-Mack]

Update on my issue, I removed the two most rearward body mount bolts, as they can be easily accessed from under the rear bumper, and sure enough the bolt holes on both sides were offset to the right rear inside the mount indicating the body was not sitting on the chassis squarely. I loosened six of the body mount bolts under the vehicle (leaving the two under the front bumper tight and in place) and was able to walk the body over so the bolt holes in the body mounts were centrally located. Rechecked the position of the body relative to the wheels and axles and everything is in much better alignment.

Surprisingly, the large body mount bolts were not very tight so I torqued everything back up and rechecked under the vehicle to make sure anything that moved with the body isn’t interfering or fouling with something else. The relative movement of the body to the chassis after the adjustment was maybe about 1/4” or so but it was enough to straighten things up and make the body sit more squarely on the chassis. Pedantic maybe, but it looks like it should now with the rear wheels spaced even in the wheel arches.

 

[trobex]

After reading your post, I checked mine this morning and it seems to be 'dead straight' in terms of alignment. So what you have done, sounds to me like a good fix!!! Maybe IA should employ you! Pity about their RHD Drivers Side Footwell designer... that kid cannot be helped!

 

[Phred]

Late Friday or early Monday build…

 

[C-Mack]

After reading your post, I checked mine this morning and it seems to be 'dead straight' in terms of alignment. So what you have done, sounds to me like a good fix!!! Maybe IA should employ you! Pity about their RHD Drivers Side Footwell designer... that kid cannot be helped!

If you think about how these things come down the assembly line I can see how when the body is dropped onto the chassis there is enough play in the body mounts, and tolerance in the metal cups that house the rubber bushings the body sits on you could get a tolerance stack of up to 1/2” or more front to rear it and would make the body sit crooked. I’ve had plenty of old school body on frame vehicles and always check for this kind of stuff as the factory is not going to take the time to make it perfect. They have a given tolerance they work within and if it’s within spec all is good.

Most folks are not going to notice anything is out of alignment and since it doesn’t impact vehicle operation or functionality nothing is usually done about it. I wager there are a number of Grenadiers out there tweaked to one side or the other just from how they were mated together on the production line. First world type of problem for sure but you pay enough for these vehicles it’s nice to have it sorted right.