Before the SWAP meet and any other future repairs/upgrades I'd like to know what I have/should have. I've looked on CB.com and I can find examples but not a complete graph. Broncohio had something close but no axle info. Any help from you all would be appreciated

Glove Compartment Door (numbers match the diverside ID):

U15GLK53673
092 6 U150 9U C B8
74

I know:
6=Bright Med Blue
U150= 3900 GVW
C= 3 speed


I was told by the PO that it was a 71. I just assumed it was. Is it a 74? I was also told by the PO that the 3 speed was swapped out for a C4. Assuming the axles are stock, what are they? I posted up pics a few weeks ago and was told the rear was a medium duty (big bearing w/ 10" drums)
Any additional info would be awesome. Thanks!

The rear axle code is for a 3.50 with limited slip but as I understand, the LS was good to about the time you drove off of the dealer's lot before it started slipping full time. There's no J so that would mean manual steering. I've attached something from JBG that may help you further. Is it possible the 74 you see is the DSO (District Sales Office), if this is your case, the truck was shipped from Michigan to Seattle.

Does the sticker on the door post say anything about federal emissions for the model year? e.g. 1971 or 1974.

Hope this helps.

Dec '70 which makes it a '71
GVWR for U150 was probably 4300lbs by '71
9U is parchment buckets with rear seat
B8 is 3.50 gear, 2780lb rear axle (small bearing) with track-lock
74 is DSO code, Seattle

Awesome guys, thanks.

So does the following rear axle look like a small bearing? The PO had a camper on it so maybe he put on a medium duty. I've looked for a tag but its long gone. Is there a stamp I can look for?

Suppose the track lock is in there. Repairable?

Thanks.

That's a big bearing hump. Rear axle isn't original. If you pull the driver's side axle out and look at the spline wear pattern you can tell if it has a track-lock. Open diff has one wide spline contact pattern. Track-lock has 2 narrow ones.

TracLoc is repairable but why? You can replace the clutches, springs and such or at least you used to be able to get the parts to do it. If I remember correctly you had to look the case over real well to look for cracks that would lead to premature failure, but I could be thinking of something else. The old TracLoc's you could wear the clutches out in one weekend of hard abuse.

Yep. Track-lock is not very durable. Good for mall crawlers. Currie makes a billet clutch cover for them. If you have one I say just run it until it breaks, then buy something else.

I thought I'd do that simple gear test to see if it was a 3:50 and then later figure out the trac lock issue.

I jacked up the rear, put it in neutral and spun the tire 1 rotation and counted how many times the drive shaft turned. It came to just under 4 1/4 so I'm guessing its 4:10 ish? Then I did the same to the front (except I locked the hubs and put the t-case in neutral) but got 2 drivehaft turns for 1 tire rotation. I must be doing something wrong.
Did I do the rear correct (given its probably open)?
What am I missing on the front (open diff too)?

Thanks again!

What was the tire doing on the opposite side? Try the rear again with only one tire in the air.

Rear (with driver rear tire lifted): 1 tire rotation = 2 1/8 driveshaft rotations

Front (with driver front tire lifted): 1 tire rotation = 2 driveshaft rotations

I may have to go back and do a little research with open diffs.

Thanks again!

That be roughly 4:1. With only one tire able to turn it has to go twice as fast as normal. Makes for better burnouts.

The really good news for you is that your planned upgrade to 33's should make your gearing just about perfect.