A shocking message

I have a 1999 Dodge Caravan 3.0L V6. I am towing a folding trailer and have
other camping stuff loaded in the back.
Between these two situations I find the rear of the vehicle sits quite low.
Should I consider getting stronger beefer shocks in the rears or are the
factory ones generally good enough? Can one put stronger shocks in without
negatively affecting the ride of the vehicle?

Any suggestions?

thanks.

 

Ride height is controlled by the springs, not the shocks. Raising the back
end of a vehicle using shocks is not a good way to do so. Shocks aren't
supposed to carry the load of the vehicle, the springs are. Putting that
sort of stress on the shock absorber mounting points might cause them to
fail.

You need to evaluate how much weight you're trying to move around and
compare that figure to the GVWR. It sounds as though you're overloading the
vehicle, which has a nasty tendency to bite you on the a** when you're least
expecting it. You need to find out what the tongue weight of the trailer
is, as well as its overall weight. You also need to find the weight of the
cargo, including the passengers. Compare these figures to the ratings in
the owner's manual. If you're anywhere near the maximums indicated, you can
assume the vehicle is being overloaded. In hilly terrain, this can have
disastrous and perhaps even fatal consequences.

You can sometimes improve things with 'helper' leaf springs to pick up the
ride height. This might alleviate one factor in your situation, but note
that this modification wouldn't do *anything* to help, say, braking
performance, another serious factor (which might be alleviated with trailer
brakes, for example). And with a 3.0L/4 speed engine/trans combination, you
can safely assume that you will significantly shorten the life of the
drivetrain if you're overloading the vehicle. There's apparently not a lot
of tolerance in the design for this; 'tis one of the reasons why people on
this newsgroup find themselves rebuilding blown transmissions.

So my suggestion is that you take a very serious look at what you're trying
to do with this minivan, and try to decide if it's really up to the task
you've presented. Good luck.

--Geoff

 

If you can, try moving some of the stuff to the trailer, but do not put
excessive weight in front of the trailer axle otherwise you will still have
the problem.. putting excessive weight behind the axle is treacherous.. you
can get devices that will measure downforce on towing hitches. they are
useful for distributing weight properly acrros the whole train..

 

I don't do any towing, but I had the rear springs in my 94 GC beefed
up with an extra leef in each rear spring.

The reason I did it was that the original springs are SHIT!!!!!!! Even
with the slightest load in the read of the van - even a small bike
rack and two bicyckes - the rear of the van would go WAY down. To the
point that driving onto a ferry deck at low tide would cause the back
of the van to bottom out! (((

That extra leef was AMAZING! The shop told me I will now have an extra
400 pounds of tongue weight above factory spec.

And I went camping a few weeks ago with the van FULLY LOADED. The
height of the rear end did not even budge more than an inch! In fact,
the van actually looks "jacked up" - which it is not. (Why would
anyone jack up the rear of a front wheel drive?? lol!).

I and very happy with the upgrade, and I am sure that I will never
have any problem towing small trailers for short periods of time (like
for moving and stuff), should I choose to do so.

hth

 

You may never have any problem towing, etc., but be prepared to start wearing
out front rotors and brake pads considerably faster than you have to this
point. I had a '92 T&C and I, too, was not happy with the rear leaf springs and
excessive sagging with hardly anything in the back. I did some research and
found that Air-Lift had a system available that would compensate for this when
installed. Bought it, installed it and solved the problem --- or so I thought.

The recommended minuimum pressure was 25 lbs. but I felt every little bump.
More pressure gave a harsher ride. No pressure was still stiff but mostly
acceptable so I left them on. I then started going through rotors and pads as
if they were paper but the rear shoes and drums rarely showed any wear. Found
out the reason was the "brake proportioning valve". Without the rear end
lowering as weight was loaded the valve was not allowing the brake system to
compensate. As a result I was essentially stopping using only the front brakes
whenever the van was loaded or I was towing a Coleman camping trailer. I
removed the Air-Lift system and then traded the van in '96 for a T&C LXi that
had the height-adjustable shocks.

 

Is that really true about the proportioning valve? I did not think they
changed their proportioning action due to weight or positional changes.
Are you sure that the extra wear was not due to the fact that you
started towing and carrying those heavy items more (rear brakes aren't
going to wear as fast as the fronts anyway, so you wouild have noticed
the fronts waearing out faster)?

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Yes, that is really true about the proportioning valve. I had the van for
almost four years three of which had the Air-Lift system. I towed the camping
trailer a total of three weeks over the three years and I had the van full of
people and kids that would probably total six weeks of those three years. The
van had close to 80,000 miles on it when I traded it for the '96. In that time
I replaced the front brakes and rotors six times and traded it with the
original brakes on the rear. The last time I had the front brakes replaced I
asked why the van had worn out the front so many times. The technician
explained that the proportioning valve was there to compensate for heavier
loads so the rear brakes would be applied equally as more weight was added. He
further explained that with the Air-Lifts keeping the rear end level I was
essentially fooling the system into thinking there was no added weight hence
the majority of brake pressure was absorbed by the front brakes. Made sense to
me then, makes sense to me now. I leave it up to you and anyone else to draw
your own conclusions. I only posted the response based upon my experience.

 

I am with you on this one Bill... I remember in the old days when front
disks were new on cars in the US , Chrysler at least used to put a valve in
the front brake circuit,,, think it was called a "metering" valve.. don't
remember for sure,, long time ago), haven't worked on many cars in the last
30 years or so.... and it's purpose (again as I remember) was to balance the
front and rear wear by restricting flow to the front disks until (30 lbs or
so?) to over come the return springs on the back shoes before the disk pads
were applied.. there of course was also a proportioning valve on the rears
also.

Just guessing by this memory, I suspect that "light and often" braking would
contribute to the extra front wear without this device, but I really don't
know.. I am sure Stern will have something to add.

I remember my father in law bought a Saab 96 (1969 in 1969)and that car
really needed such a device as it went through pads about every 5000 miles,
but that is another story.

Some one with an old service manual may be able to comment,, as I think you
had to put a clip on this "metering valve" in order to bleed the brakes with
the old block the pedal down part way and let it drip method...(then again
all from memory)

Anyone?

 

That would go along with the normal proportioning valve action - it
would have two slopes (in curve of front pressure vs. rear pressure) and
a changeover point, called a "split point", at the vertex of the two
slopes.

I'm really skeptical about that part of the tech's explanation - but I
very well could be wrong.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

I am NOT here to debate - I only posted from experience. I only know what
happened with my van. I only posted as a "heads-up" FYI piece. I haven't had
the van for 8 years. Whether that was the cause for going through front brakes
and rotors the way I did no longer matters. I do know that for the first year
of ownership I put about 29,000 miles on the van and replaced the front pads
and rotors at 28,000 miles. I then replaced front pads and rotors five more
times over the next three years (after the Air-Lift installation) which
averages out to every 10,400 miles.

BTW - In posting this reply I remembered why I finally removed the Air-Lift
system. I called Air-Lift to explain what had occured with me and was told that
they had discontinued this item. They had discovered through their testing and
calls from consumers that it caused problems with the braking system and ride
quality on these vans.

RP

 

Nor I. I'd really like to know the answer about the proportioning valve
sensing vehicle level - hoping someone in the know would post.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

I know nothing about Chrysler minivan brake systems but I can tell you
that that is exactly how the prop valve works on a FWD VW so it is not
outside the realm of possibility. (especially since Chrysler took a few
pages out of VW's notebook over the years.)

nate

 

I haven't looked at either of my vans that closely, but my last two
pickup trucks have a proportioning valve that senses the load. It is a
rotary valve mounted on the rear axle that has an arm that connects to
the bed of the pickup. As the truck is loaded, it is supposed to bias
the brakes more and more towards the rear. So, in this case having air
bags or other load leveling devices would defeat this proportioning
system. I wouldn't be surprised that minivans would have this, but I've
never crawled under mine to take a look.


Matt

 

Never heard of it !... thanks Matt !!!!,, going to have to crawl under the
van now for sure,,,, well maybe not..

Ted

 

I'd really like to know the answer about the proportioning valve

I didn't realize that proportioning valves had gotten that complex (or
sophisticated, depending on your point of view) even if it's so for only
a limited number of appliations. I learned something. Thanks!

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

I still haven't felt like looking under my minivans, mainly because I
can't get under then without jacking them up, but I did go pull out my
service manual (genuine Chrysler manual). From the description and the
pictures, it does NOT appear that the 1996 minivan has a load sensitive
proportioning valve. I do not see any linkage on it that connects to
the rear axle. Just two lines going in and two coming out.


Matt

 

Look at this link under "mechanical proportioning valves" for a
description of the height/load sensing valves.
http://www.babcox.com/editorial/bf/bf50014.htm

Matt

 

Thank you Matt !!!!

Man did I learn a bunch... and why the new cars (FWD to be specific) don't
have the "metering" valve...been wondering about that one.

Enough people like you around I just might get smart before I die.... .. ..
... nah,, I know there isn't enough time left for that anymore,, probably
never was... but,, 1 less thing I am totally ignorant about !!

Ted

 

Interesting. Thanks!

That article indicates that the typical height sensing valves are
adjustable for changes in ride height. Perhaps that is the answer for
those who add helper springs or air shocks. However, stiffening the
suspension will decrease the sensitivity even if it is adjusted to
compesate for neutral height.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")