Lock Right Install in Iron 7.2 Front Diff

Miles · Post by **Miles** » Fri May 11, 2007 4:50 am

This write-up will cover the install of a Lock Right locker in the Iron S-10 7.2 front differential.

1.) With the front diff removed and drained of oil, you can set the diff on the drivers side, and remove all the bolts that are around the perimeter of it: CLICK

2.) With all the bolts removed, use a large screwdriver to help separate the two diff halves. CLICK

3.) Lift the diff carrier out of the housing, and thoroughly clean it with Brake Clean. Remove the center pin lock bolt: CLICK

4.) Turn the carrier over, and carefully secure it in a vice. Loosen & remove the ring bolts. CLICK

5.) Using a brass punch & hammer, tap very lightly around the perimeter of the ring, so as to remove it from the carrier. Be ready to catch the ring, so that it is not "dropped" on the vice and possibly damaged. CLICK

6.) Remove the carrier from the vice, and flip back over. Using your finger, simply push the center pin out of the carrier: CLICK

7.) To remove the spider gears, simply push on one of the spider gears and they will roll to one side. Be VERY careful to not let the side gears fall or get mixed up with one another. This is especially important in the next step. CLICK

8.) It is incredibly important that you place the side gear shims on the outer Lock Right side gears, and replace them in the EXACT same side of the carrier that they came out of. If they are visibly worn, then you need to replace them. CLICK

9.) Place the four supplied Lock Right dowel pins in their appropriate slots in the inner Lock Right side gears. You might use some assembly grease to keep them in place during installation. CLICK

10.) Secure the carrier back in the vice as shown. Then install the inner & outer side gears & inner spacer all together on one side first, and just the outer side gear on the opposing side as shown (note: the inner side gears must be installed in the carrier with the flat sides facing up & down): CLICK

11.) Install the opposing side inner side gear & inner spacer as one assembly, with the flat sides facing up & down. This part is somewhat tricky, so go slow & take your time. Also, the inner spacers can only go in one way so as to allow for enough clearance for the center pin.

12.) Slide all four dowel pins over into the opposing sides of the inner Lock Right side gears as shown: CLICK

13.) You can now reinstall the center pin in between the inner side gears & inner spacers. You may need to slide the inner spacers inside the side gear assemblies, so that the center pin can slide in. If the inner spacers do not slide inside the side gear assemblies all the way, you may have them in backwards. This center pin can only be installed one way, because there is only one hole in it where the center pin lock bolt goes through it. Make sure the hole in the center pin is lined up with the lock bolt hole in the carrier during installation. CLICK (NOTE: I took this pic before I had installed the dowels. Just know that they should already be installed before you install the center pin.) You can also temporarily screw the center pin lock pin back into the carrier, so that the center pin will stay stationary while you install the springs.

14.) Insert all four small springs inside all four of the larger springs, so that they are four total spring assemblies, rather than 8 separate springs: CLICK

15.) Using a scribe, carefully insert the spring assemblies in the wide dowel pin holes as shown, behind the dowels. It is very important that the springs snap all the way down into these spaces, otherwise your Lock Right may not function correctly. CLICK

16.) It should look like this when you are finished installing the Lock Right in the carrier: CLICK

17.) Using a new center pin lock bolt, put red Loc-Tite on the threads, and torque it to 24 ft. lbs in the carrier. CLICK

18.) Reposition the carrier in the vice, and reinstall the ring back on the carrier. Using a cross pattern like what you use in tightening your lug nuts, SLOWLY tighten up the ring gear bolts. This part may take awhile, as it is important to NOT tighten one side more than the other. It must be re-pressed back on the carrier evenly, and it is the tightening of these ring bolts in a cross pattern, that presses it back on. Once the ring gear is tight, torque the bolts in a cross pattern to 59 ft. lbs. CLICK

19.) It is imperative that you have new carrier bearings pressed onto the carrier before you re-install the carrier in the diff.

20.) Remove the old carrier bearing races from both diff housing halves. Thoroughly clean the inside of both diff housing halves with Brake Clean, and clean the mounting surfaces very well with a razor blade. CLICK & CLICK

21.) Install the new carrier bearing race in the drivers side diff case. Set the carrier back in the drivers side diff case. The teeth of the ring should set inside the teeth of the pinion: CLICK

22.) Using Permatex Ultra Copper Seal, put a good bead around the perimeter of the drivers side diff half: CLICK

23.) Use some assembly lube on the other carrier bearing race, and install it in the passenger side case half. Carefully set the passenger side case half back on the drivers side case half. If the case does not set completely flush, something is not right. Just be careful not to let the passenger side carrier bearing race drop out. Install the case bolts back in the diff case, and torque them to 37 ft. lbs in a cross pattern.

24.) Ta-Da! Here is a few pics of the completed diff: Pic 1 & Pic 2

***If you intend to install this locker in the front diff, I would HIGHLY recommend running 1 Ton Idler & Pitman arms from a 1992 Chevy 1 Ton 4WD, to keep the tires pointed straight while in 4WD (...frame mods necessary for this steering upgrade). Secondly, I would VERY highly recommend installing the newly designed one-piece Posi-Lok cable, in place of the factory vacuum actuator for the front diff. This will give you the ability to manually engage, and disengage the passenger side axle shaft & tire. Makes for much easier turning on the trail, and alleviates stress on the idler arm, when that tire is not necessary to be engaged. Lastly, I would also recommend installing a quality steering stabilizer, like the Rancho unit that is available for our trucks. This will help absorb the side to side impacts that the idler arm normally has to deal with on its' own, while in 4WD, in high torque situations.

If you happen to already be running the 1 Ton Pitman & Idler arms, now would be a great time to clearance the front face of the diff, so that the center link will not contact it. I removed about 1/4" of material. Here is what it should look like when you are done: CLICK

Aside from installing the Lock Right, it would be a good idea to go ahead and replace your axle seals while the diff is out of the truck. Check any other seals & bearings for wear, and replace as needed.

gocntry · Post by **gocntry** » Fri May 11, 2007 10:39 am

Nice Write Up.
I've Been Watching Your Build On Txzr2, You Did An Awesome Job With Your Build And Staying Stock Looking.
Can't Wait To See The 231 Swap. (I've Been Waiting To Try This In My Crew). And Can't Wait To See What Your Blazer Is Capable Of At The Zr2 Meet In August.

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 11:20 am

Ok- I have a spare front diff in my shop (e-bay - $65 shipped). I have been thinking about trying to swap to 4.10 gears in it myself just to see if I can do it - thanks for the step-by step.

Question - How do we tell if we have that "iron" diff?

Post by **HenryJ** » Fri Jun 22, 2007 12:35 pm

adrenalnjunky wrote:How do we tell if we have that "iron" diff?

They are usually painted and a magnet will stick to them.

F9K9 · Post by **F9K9** » Fri Jun 22, 2007 12:51 pm

We don't have iron diffs, to the best of my knowledge. I participated in his survey.

Post by **HenryJ** » Fri Jun 22, 2007 1:02 pm

Crew cabs, no. Chris has a four door Blazer. Could it have one? Or the ebay diff he bought?

F9K9 · Post by **F9K9** » Fri Jun 22, 2007 1:20 pm

Chris?

Sorry, I got lost somewhere. I thought that most of the iron diffs were in ZR2s with 5 speeds and possibly some Bravadas,

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 2:00 pm

Chris = Me

4 Dr Blazer owner

And if I remember right the Safari/Astro with AWD also was a potential source of the iron front diff.

Honestly, I haven't even opened the box that the ebay unit came in - and it's been almost 2 years.

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 2:01 pm

HenryJ wrote:..... and a magnet will stick to them.

DOH! 4th grade science fails me again!

F9K9 · Post by **F9K9** » Fri Jun 22, 2007 2:03 pm

Sorry, I was always bad with names and I know that Jeremy didn't touch on Astros but, knew that some had the iron diffs.

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 2:08 pm

I checked, my spare is alloy.

F9K9 · Post by **F9K9** » Fri Jun 22, 2007 2:47 pm

Was that a difficult box to open, BTW?

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 4:25 pm

lol - nah, just didn't have a reason to

Now that I've seen the step by step on splitting and rebuilding - I'm going to start researching 4.10's again. I've got 3.42's in my truck now, open rear diff, no G80.

Mainly I'd like to be able to go to 31's and try and recover some of my fuel mileage - I'd even stay with 30's if it would get me back into a respectable MPG rating.

I'm guessing a lockright and the aluminum case is a bad idea.

F9K9 · Post by **F9K9** » Fri Jun 22, 2007 5:12 pm

adrenalnjunky wrote:l....................I'm guessing a lockright and the aluminum case is a bad idea.

I am guessing the S Series platform and good gas mileage is like mixing oil and water

I remember a road trip, a gentle foot and gas prices got me 22 mpg in a real Z28 34 yrs ago. A gentle foot, gas prices,and a flat state got me 20 mpg one time with a trip to IN in my '97 ZR2. Hit 20 mpg in my CC one trip and would not want to relive the nightmare again

adrenalnjunky · Post by **adrenalnjunky** » Fri Jun 22, 2007 5:23 pm

Yep- I've been driving the 4.3 since my GMC Jimmy in 1989 - I love the 4.3, but it's thirsty - especially in the gear-ratio and tire size I'm spinning.

Plus i keep getting an intermittent DTC - PO420 - Service Engine light - it's been happening for over a year now. It started showing up after I had my catalytic converter replaced after the stock one came apart inside. DTC says the left bank catalyst is below normal efficiency or something - bit I'm leaning towards it being a bad O2 sensor. Never seem to have the time to look at it. Cant be helping fuel mileage though.

Miles · Post by **Miles** » Sat Jun 23, 2007 10:08 am

If you plan to run 31's, I'd personally step up to 3.73's, not 4.10's. The 4.10's will give you more power, but will negatively affect gas mileage on the highway. On my old 92 GMC Jimmy 4x4 w/30's, I stepped from the factory 3.42's, up to 3.73's, and it was like driving a whole nother vehicle! Power increased significantly, as did my mileage.

On my Blazer w/33's, I've gone back and forth between the 4.10's & 4.56's. 4.56's would be nice for more low end grunt off-road, but it would affect my mileage too much on the highway. I've decided to just install a 4:1 low range gear set in the 231 x-case I am going to swap in instead, and install 4.10's to better match the 33's. I'll never run 35's on these axles.

Through that Iron Diff Poll, we learned that most all '98+ S-10 4x4 Pickups, that came equipped from the factory with a 5-speed tranny, got the iron front axle (ZR2 or not). The "magic" combo is a 5-speed tranny, coupled with the 3-button NP-233. Since all S-10 Pickups after 1998 only have one option for a transfer case....the 3-button NP-233....all you gotta find is one that has a 5-speed.

adrenalnjunky · Post by **adrenalnjunky** » Sat Jun 23, 2007 3:32 pm

thanks Jeremy - sounds like I need to check out the local u-pull-it salvage yards