Hello everyone and Happy Holidays.

I've been getting some things checked out on my new truck over the last few days and have come up with some questions...... the truck is a 1986 F250 XLT Lariat, 2wd and SRW, 6.9, C6 tranny

The Questions:

1) Is there an easy way to identify what rear diff I have? I can't find a tag on the cover or the sticker on the driver's door. It is some sort of limited slip set up if that helps any.....

2) Parts stores and that keep asking me about which rear brakes I have, heavy duty or light duty... they look pretty heavy duty to me but I am used to working on mostly smaller/lighter vehicles. Any suggestions of how to determine what I have?

3) As I said before, my experience working on vehicles is mostly limited to passenger cars and light truck (1/4 and 1/2 tons) so some things are a little different. My truck was once used to haul a cattle trailer and has 2 different trailer brake set-ups. The first is all electrical and I am familiar with that system. The other I am not familiar with. I think is is for some sort of vacuum assisted hydraulic trailer brakes. I has a controller in the cab attached to the steering column, some sort of distributer/proportioning valve on the right front inner fender with "air brake" lines taking vacuum from a tee next to the trucks brake booster to the valve in the engine compartment via the controller in the cab and then back into the box where the 5th wheel hitch used to be. it also has a line teeing of the brake line coming out of the rear brake portion of the master cylinder going to the engine compartment valve unit.
Am I on the right track here as far as my understanding of this particular trailer brake system? Is this something that is still common on trailers? It doesn't have the 5th wheel set-up anymore and I don't have any plans of getting it rigged up for one so I'm wondering if it's worth keeping on the truck or just remove it all? I think I'm at least going to disconnect it as it increases the possibility of a vacuum leak....

Any thoughts are much appreciated!

 

I'd think you'd have a 10.25" rearend if you have a HD truck.

For your rear brakes, block your front wheels and jack up one rear wheel, or both. Pull the wheel off. Pull a brake drum off. Measure the width of your brake shoe. 3" = Heavy Duty. 2-1/2" = Light Duty.

I've got an oldschool trailer brake setup. It's some odd lever that moves back and forth when you hit the brakes. I haven't had a trailer on this truck because I didn't really have brakes. That's how I found out I have a HD truck because of those rear drums and shoes. Not sure about your trailer brakes.

I believe the HD's have 9/16" wheel studs and the LD's have 1/2" studs. I could be wrong.

 

All diesel engine trucks were classified Heavy Duty.

Rear axle fill plug, if it is on the driver side by the pinion than it is a Sterling 10.25".
Rear fill plug on the rear cover of the differential, Dana 60 more than likely.

Probably the Sterling axle, which should have 3" x 12" brake shoes.

I have actually seen a couple trucks from the early 80's that had hydraulic over air brakes on the trailer.
Not something you will find today.

I would probably get rid of thet system and go with electric only for trailer brakes.

 

That is vacumn over hydraulics only found on some heavy goosenecks and not even very popular on the heavy trailers anymore. they are in my opinion a better brake system but more complicated than straight electric so they are going the way of the dinosoar.

 

Thanks folks! That's very helpful...

Dave S: fill plug is on the driver's side by the pinion so Sterling 10.25" it is with 3"x12" brake shoes. I'll have to confirm next time I pull a wheel off.

Dave S and starmilt: great information... I think I'll just remove it all

Thanks again

 

About like that hydraulic over air system.
The only part I would keep is the air compressor and tank.

I don't even know where I could buy parts for the hydraulic part of the system.

 

Dave his is vacumn over hydraulic so no pump and tank. parts are still available but the systems cost more than electric and are not very popular anymore. I have seen auxillary vacumn pumps but usually they use the existing vacumn.

 

There is no air compressor or tank..... just vacuum using the existing vacuum pump (there is a tee in the vacuum line just before the brake booster)

Dave, when you say all diesel engine trucks are considered heavy duty... does this also apply to u-joints? Just went to the parts store to get one and they asked if I wanted the standard or heavy duty u-joint...... they are slightly different and the truck is an hour away in my dad's barn so I can't just run out and check.

Thanks again everyone

 

Diesel F 250 trucks share the same frame and drive line that are in F 350 trucks.

The only difference is the front axle and the blocks between the spring and axle on the rear.

250 front axles are IFS Dana 44 or 50 axles.
350 front axles are Dana 60 straight axles.

250 rear spring blocks are 2"
350 rear spring blocks are 4"

Looking at your avatar, looks like your truck is an extended cab.

You should also have a two piece rear drive shaft, so the wheel base would be relevant info.

Some parts stores have heavy duty U joints and regular U joints for the same application.
Cap diameter and cross width are the same for both joints though.
The cross may look a little different, or may be grease able or non grease able.
So without more info that question still can not be answered.

Where are you shopping?
A national store like Autozone that has a web site?

 

I had some other stuff to pick up as well so I checked a few things out at Canadian Tire. And the differences were more than just superficial.
The 'standard' u-joint's end caps had a smaller diameter than the 'heavy duty' u-joints. So, while they are listed for the same application in Canadian Tire's system is seems obvious to me that they are not for the same application. If I had the truck here I'd just run out and measure but as I said before it about an hour away, I thought that someone may have encountered this before.

As far as the wheelbase is concerned.... I'm not certain what the exact measurement is but it is a long box extended cab truck with a 2 piece driveshaft.

 

At NAPA
Precision U Joints

Regular strength, regular zerks, greasabe

At transmission PUJ 434 $17.49 uses U bolts or straps
At transmission PUJ 354 $16.99 uses clips

At carrier bearing PUJ 354 $16.99

At axle PUJ 434 $17.49

Super Strong, needle zerks in caps, greasable

At transmission PUJ 265 $26.49 uses bolts or straps
At transmission PUJ 270 $27.99 uses clips

At carrier bearing PUJ 270 $27.99

At axle PUJ 265 $26.49

I looked at the measurments on the crosses and caps.
Both are the same for all of the listed joints for each application.
I only posted the greasable numbers.

The only thing you will have to know is if you have a slip yoke at the transmission or a slip joint in the drive shaft and bolt to a transmission flange.
They list it both ways for the three joint two piece drive shaft.

 

Thank you Sir!

I'm heading to Napa when I get back in town!

It seems to me there is a fault with Canadian Tire's part inventory system.... because the caps on the 'regular' u-joint were obviously smaller than the 'heavy duty' u-joint.

Thanks again... a man with such a wealth of knowledge is the best tool another man can have!

 

I got that off of the NAPA website, so I guess I better hope their numbers and joint info listed is correct.

I usually have good luck with the info I pull off of their site though.

 

And all this time I thought you got all this from memory!

 

Single piece driveshaft in mine, so not from memory.