Truck Origin

[redneckchevy9]

The truck I drive for work is a '91 FORD LTS9000. Is there anyway of figuring out what chassis is began it's life with? I read somewhere that the 9000's were mainly used for semi, but of course that could be wrong. I am just curious to see how this truck was configured before it was stretched and made into a boom truck. I am not sure if this is a clue or not, but I have this switch on my dash & I'm not really sure what it is for. It is not the diff. lock because that switch is on the left side of the dash.

 

[Raildudes dad]

5th wheel lock? I'd have to go look at my 87 LTL9000 tractor to see if it's the same. Your local Freightliner dealer should have the microfiche on the truck as built from the factory. Take in your VIN and they should be able to look it up. That's how I found out mine came from the factory with a CAT. (It was repowered with an 82 Cummins at one time) . Freightliner has the Ford / Sterling records.

 

[Oxbow]

I have no idea what that switch is, but some of the older trucks (up until 70's perhaps) had limiter swithces for steering axle brake application. :beatsme

 

[51kw]

That should be the switch for the posi traction. Use when normal diff lock is already on.

 

[Tiny]

That should be the switch for the posi traction. Use when normal diff lock is already on.

I believe this is correct . I know you have flipped the switch and prob nothing happened . Just wait for the next sloppy spot and try it LOL

 

[FWD]

It's for locking up all four drive wheels or just three, but usually they are set for both drive axles. Just make sure you don't engage it while the wheels are spinning. Unlock it as soon as you are out of the slippery area. They usually kick out themselves once you are over 20 or 25 miles per hour.

I know a guy from Prophetstown. He lives and works here. Still goes back to Illinois as has people there yet.


FWD

 

[redneckchevy9]

It's for locking up all four drive wheels or just three, but usually they are set for both drive axles. Just make sure you don't engage it while the wheels are spinning. Unlock it as soon as you are out of the slippery area. They usually kick out themselves once you are over 20 or 25 miles per hour.

I know a guy from Prophetstown. He lives and works here. Still goes back to Illinois as has people there yet.


FWD

Really, is sure is a small world. I am sure they don't like speed, just like when locking your rear end.

 

[redneckchevy9]

5th wheel lock? I'd have to go look at my 87 LTL9000 tractor to see if it's the same. Your local Freightliner dealer should have the microfiche on the truck as built from the factory. Take in your VIN and they should be able to look it up. That's how I found out mine came from the factory with a CAT. (It was repowered with an 82 Cummins at one time) . Freightliner has the Ford / Sterling records.

That's what I thought & that's what made me question is the truck started as a tractor & later converted to a longer WB truck.

 

[redneckchevy9]

I believe this is correct . I know you have flipped the switch and prob nothing happened . Just wait for the next sloppy spot and try it LOL

Damn, if I had a smart phone, I could've seen these post this morning & used the advice. 1st decent snow of the year yesterday & first thing this morning, had the front wheel sink in the grass at a jobsite about 8". Even with the rear end locked & no weight on the truck, the drives couldn't catch anything but slippery snow, so I couldn't even pull steer axle out of the holes. 5minnutes later I was moving again, but I thought not a good way to start the winter.

 

[redneckchevy9]

5th wheel lock? I'd have to go look at my 87 LTL9000 tractor to see if it's the same. Your local Freightliner dealer should have the microfiche on the truck as built from the factory. Take in your VIN and they should be able to look it up. That's how I found out mine came from the factory with a CAT. (It was repowered with an 82 Cummins at one time) . Freightliner has the Ford / Sterling records.

I did some looking around on google & found www.fleet.ford.com/maintenance/vin-decoder. Come to find out, the truck was a 382" WB & the CAT that is in the truck is what it came with.

 

[ValleyFirewood]

I'm guessing that the other switch you aren't showing is for the PDL and the switch in the photo is for one or both axle diff locks.

 

[redneckchevy9]

Here is the switch I am not showing you - my diff. lock switch

 

[redneckchevy9]

I believe this is correct . I know you have flipped the switch and prob nothing happened . Just wait for the next sloppy spot and try it LOL

I flipped today when sitting still (I've never flipped it on before). It must run on air because I got a little hiss when I turned it on.

 

[Tiny]

Sometimes it is easier to call that in this last pic an inter axle lock .

Much like the single spinner rear axle on a pickup the diff lock out works the same way . That is , which axle turns the easiest gets the bulk of the power . But in the slick stuff that works out as one axle spinning and the other doing nothing . That's when you bring everything to a halt and flip the diff lock . You will have both axles pulling equally .

You appear to have a wheel lock switch also , That switch is suppose to act like a locking mechanism . Working correctly you have posi trac in a big truck .

I am guess that your truck must have walking beams under it. That's probably the only way you wouldn't know what the diff lock did by now .

Now before you think you have a new found 4 wheel drive , Here are a couple of warnings . If you forget about the diff lock and run it on pavement , that is not the end of the world . It's not recommended on dry pavement and extend use will heat things up .

The wheel lock is complete different . It's for slick stuff only and for all practical use straight a head only . 1st time you get everything locked you will find that turning is next to impossible .
If you are spinning and one corner finds a dry spot ... If your lucky you only break an axle .

The wheel lock is a good option to get you out of trouble but if you have the Idea that you will kick all this in and plow thru mud or snow like a dozer your going to be highly disappointed stuck ... umm D9 stuck

 

[redneckchevy9]

I am guess that your truck must have walking beams under it. That's probably the only way you wouldn't know what the diff lock did by now .

That is correct, a spring ride Hendrickson - no air unfortunately. Rides pretty good if you put 8,000lbs or more on it. I understand everything you are saying about the use & non use of it. In 10yrs, I have only had to lock the rear end a few times driving slowly down a very icy road. I understand that locked axles & rear ends don't like turning, especially on dry stuff. In the words of my grandpa, 4wheel drive only gets you 50yards more stuck.

In a nutshell, if I just flip the "inter axle lock" switch, just the rear drive axle is pulling. Flipping the "wheel lock" switch makes the front drive axle pull also correct?

 

[Fastdirt]

I have both those switches in my L9000. Greatest two switches ever. You lock those two switches and your unstoppable or you will be digging eight holes at once. Every truck in the world should have those double lockers. So true what Tiny said, if you get her stuck with all 8 tires pulling you're gonna be "D9 stuck" LOL. It will understeer while locked so use your head and you only get one or two tries before it's all over....

 

[ValleyFirewood]

Yes, they can run on air, but the way you think it works isn't correct.

With everything unlocked... ie open differentials you can be in a situation with only power to 1 set of drives out of 4.

Turn on the power divider lock (PDL) (interaxle diff lock... same thing) and you will have equal power being sent to both the front rear and rear rear axle. So you will have at least 2 sets of drives spinning.
The power divider is the unit that is on the front rear where the driveshaft goes in. It sends power to the pinion gear of the front rear and also power to the jackshaft to the rear rear axle (which goes to the pinion on that axle)

The other switch is a axle differential lock. It locks the two axle shafts in the axle. Often it's just in the rear rear axle. With the PDL and 1 axle locker you will have 3 tires with power. Some trucks do have axle lockers in both axles. I don't know if any use just 1 switch for that though.


Some of the issue is people and companies haven't agreed on what to call them so many names for the same thing.

Positrack for example is a Chevy brand of limited slip diff, not anything used on a big truck.

In a nutshell, if I just flip the "inter axle lock" switch, just the rear drive axle is pulling. Flipping the "wheel lock" switch makes the front drive axle pull also correct?

 

[mitch504]

Valley, you are close, but...

A lot of people don't quite understand open differentials, between the axles (power divider, actually an IH term), or in the axles.
When the diffs are unlocked, the truck is applying exactly equal torque (twisting force) to all 4 hubs. Just like using a torque wrench, it is impossible to apply more torque to a thing than the force necessary to turn it, thus, all 4 wheels get the torque needed to turn the one with the least traction or to move the truck. When you lock the inter-axle diff, it locks the axles' input shafts together. Thus you get the torque needed to turn the easiest wheel on one axle, and then the easiest wheel on the other axle, or to move the truck.

If you have a tandem truck that can lock both axle diffs, you get the torque needed to turn all 4 wheels or to move the truck.

 

[ValleyFirewood]

My explanation was a quick 5 min deal while I was waiting in line at the store. Please edit it if I put incorrect info. I just read over it again and it all makes sense to me. Pretty much says what you just said.

I suppose my use of "power" isn't the scientific one, but I think we can all understand where I was going with it.

If the truck is stuck and 3 tires are not doing anything, they are not putting power to move the truck.

 

[redneckchevy9]

THANKS EVERYONE FOR YOUR INPUT!! I feel a little silly because I just got schooled big time. I am glad that I know this information now. All the other trucks I have run have never had the axle diff. lock switch, just the interaxle diff. lock. This is exactly why I wanted to become a part of HEF, the wealth of knowledge all you guys have on here is priceless.