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Unibody benefits?

R

ReftonsRed

NAXJA Forum User
Location
Pennsylvania
I have often wondered what the benefits of a unibody 4x4 are and why Jeep decided on using this design for the cherokee. Also what are the benefits of wheeling a unibody?
 
Yeah they are lighter (in most cases) but they are not really that much more rigid that a body on frame. Excluding the subframes, the body is just thin seet steel. It really dependes on the design, quaility of materials and construction.
 
BillBraski said:
Yeah they are lighter (in most cases) but they are not really that much more rigid that a body on frame. Excluding the subframes, the body is just thin seet steel. It really dependes on the design, quaility of materials and construction.
Click to expand...
In the cherokees case how does the unibody compare in strength to a vehicle of similar proportions with a frame>
 
ReftonsRed said:
In the cherokees case how does the unibody compare in strength to a vehicle of similar proportions with a frame>
Click to expand...

The closest comparison I can make is to my old 89 Ford Bronco 2, It was a compact body on frame SUV with a smaller interior than the XJ (It seated 4), The body flexed & squeaked way more than any XJ I have been in, Even with the puny underpowered 2.9L V6 & weak axles (Dana 28 front & Ford 7.5 rear (I think?)) It weighed more than an XJ (like 600 Lbs more according to the registrations) .
I guess this is one reason why XJs are still around/Very popular & most Bronco 2 are in the Junkyard!!
 
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Bronco II to XJ is a good comparison size ....Having a full frame does have some advantages...you can put a snow plow on a Bronco II pretty easily and it makes for a great little plow truck for driveways and tight spots...and do a body mount lift quick and cheap for $100
 
One thing the railroads found out when they tried making the then new compact trucks usable for highrail use. Initially they put standard sized highrail gear on these little trucks and found that the body on frame Fords (Ranger and Bronco II) and GM (S-Pickup's and SUV's) trucks couldn't handle weight of the gear ment for the F/S trucks (normally the big brothers of the afore mentioned trucks), while our unibody XJ's could take the excess weight and not have nearly the structural and suspension problems of the other brands. If you ever watch around Union Pacific tracks you'll still see some of the later '97-'01 XJ highrails in service! The XJ did have a poor reputation as a highrail for a while, but that was mainly due to the Ford and GM trucks being lucky enough to have manufacturer's make lightweight gear for them while there wasn't being any made for the XJ's, so it was instantly a bad vehicle for a while.
 
bjoehandley said:
One thing the railroads found out when they tried making the then new compact trucks usable for highrail use. Initially they put standard sized highrail gear on these little trucks and found that the body on frame Fords (Ranger and Bronco II) and GM (S-Pickup's and SUV's) trucks couldn't handle weight of the gear ment for the F/S trucks (normally the big brothers of the afore mentioned trucks), while our unibody XJ's could take the excess weight and not have nearly the structural and suspension problems of the other brands. If you ever watch around Union Pacific tracks you'll still see some of the later '97-'01 XJ highrails in service! The XJ did have a poor reputation as a highrail for a while, but that was mainly due to the Ford and GM trucks being lucky enough to have manufacturer's make lightweight gear for them while there wasn't being any made for the XJ's, so it was instantly a bad vehicle for a while.
Click to expand...

What's "highrail gear" - is that where the rail wheels can be extended and retracted so the vehicle can follow the rails?
 
bjoehandley said:
Yup, you got it John! I think those tend to add nearly 1000lbs to the weight of a truck for the normal F/S truck equipment.
Click to expand...

I can imagine. Those solid steel wheels (or are they cast iron and ground?) probably tip around 150-200# on their own. Add in the frames and hydraulics...
 
My only complaint about XJ's is the weight distribution. They could have set the engine back 2 inches. The firewall would have been different, as its already made to fit the valve cover. I would like more of a 55-45 distribution. The XJ has pretty good strenth but the roof is a problem.I am planning on tearing apart my 93 and extend the wheel base (D44's too), putting in a cage (My boss just bought a "tube shark"!) and rework the rockers. But that won't be until June.
 
5-90 said:
I can imagine. Those solid steel wheels (or are they cast iron and ground?) probably tip around 150-200# on their own. Add in the frames and hydraulics...
Click to expand...


Not sure on the weight (I'd have to ask Dad), but IIRC they are cast and some converted trucks (no matter the brand or size of truck) have rubber wrapped rail wheels. Dad doesn't like those since them can affect the trucks ability to stay on track (literally, since those are narrower than a standard wheel) and make it harder to hear and/or feel rail damage. Overhang has an affect on highrails too, he's used a '07 4x4 Suburban highrail that on tighter curves like those on indutrial area right of ways can pull the back tires off the track and would make simularly equipped 2wd unable to go anywhere since the main drive wheels still have to provide propultion on the tracks too:doh:

He does enjoy driving that Suburban though, enough power to spin the tires at 65 on damp pavement in 2wd and can pull itself back on track if it de-rails:cheers:
 
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