Junky 1999 XJ Front Brakes

Good Day to All.
My 99 XJ brakes ( no pun intended) caliper retaining bolts on a frequent basis. I replaced the calipers and mounts and installed high performance rotors and pads... and it's still a problem. They grab, rattle and overheat and just plain stink for performance !! :-(
In a beer thirty meeting, it was suggested that I go to an earlier XJ axle with the earlier brakes to eliminate the problem. I am willing to do just that but I am asking for insight and comment from anyone who has done this swap or has knowledge if I'm headed in the right direction ... Or not.
I live in St Thomas, a very aggressive, mountainous area where the brakes are worked hard and long.
Any help with this will be greatly appreciated cause I'm done spending money on this axle.... it's Time for something that works...
Thanks....

Not sure what that second sentence was mean to say as a key word or two seems to be missing.

Caliper bolts on a 99 locate the caliper assembly on the knuckle, and unlike Early style calipers, the new calipers have the slider built into them and the bolts go though them. Those sliders also tend to freeze up and cause the caliper not to retract.

Often people over tighten and strip the bolt holes on the knuckle side. If that is what you were tying to communicate, you will need to drill out the holes to the size for a helicoil insert.

On brake usage in mountainous regions, use you engine to brake, not the brakes. Works even with automatics.

Thanks for the reply.
The first sentence was a lame attempt at humor...braking brake parts ..
Oh well
The bolts brake at the thread termination.. The pads rattle and wear groves into the sliders that I have welded and ground down for the last time.
I am wholly dissatisfied with the engineering on this brake setup and wish to be rid of it in favor of an older style setup.. It is reportedly superior to my present setup in these conditions..
I am looking for insight or experience with the entire front axle assembly swap out to the earlier and more robust/trouble free design. I have no faith in the present unit..... I'm just trying to save myself a steep learning curve with the swap.
I do have an automatic transmission, and I baby it as there are very few folks (if any) who repair them well here.
Thanks again...

If you are breaking caliper bolts, you are over torquing them. 30ft/lbs is not much past snug.

Look into a WJ brake swap.

Older 1984-89 XJ brakes should only require the outer knuckles to be swapped. Any XJ AMC or XJ Chrysler steering knuckle will fit on any XJ D30. Remember, unit hubs type, and brake caliper type, must match the steering knuckle type, Chrysler vs. AMC.


Unit Hub/Bearing Assemblies:

1) 1984 through 1989 - Original AMC hubs ( Jeep Part Numbers 4723371, 5252725, 53000228, 53000234 )
AMC brake rotors, AMC calipers, AMC steering knuckles, and AMC roller bearing hubs.
The unit hub/bearing are the same part number for both sides of the vehicle.

2) 1990 through 1999.5 - Older type unit hubs ( Jeep Part Number 53007449 )
Uses Composite brake rotors and Chrysler calipers and Chrysler steering knuckles.
The unit hub/bearing are the same part number for both sides of the vehicle.

3) 1999.5 through 2001 - New type unit hubs ( TIMKEN Part # HA597449 - Jeep Part Number 5016458 )
Uses Cast brake rotors and Chrysler calipers and Chrysler steering knuckles.
The unit hub/bearing are the same part number for both sides of the vehicle.

Steering Knuckles:

1) 1984 to 1989 - AMC Steering Knuckles. Left and right side steering knuckles have different part numbers and only accept AMC calipers.

2) 1990 to 2001 - Chrysler Steering Knuckles. Left and right side steering knuckles have different part numbers and only accept Chrysler calipers.

Any XJ AMC or XJ Chrysler steering knuckle will fit on any XJ D30. Remember, unit hubs type, and brake caliper type, must match the steering knuckle type, Chrysler vs. AMC.

Brake Calipers:

1) 1984 to 1989 - AMC Brake Calipers. Left and right sides calipers have different part numbers and only fit on AMC steering knuckles.
2) 1990 to 2001 - Chrysler Brake Calipers Left and right sides calipers have different part numbers.

AMC and Chrysler calipers do not interchange, they must be mounted on the corresponding AMC or Chrysler steering knuckle.


Brake Rotors:

1) 1984 - 1989 - AMC Brake Rotors
2) 1984 - 1999.5 - Composite Brake Rotors
3) 1999.5 - 2001 - Cast Brake Rotors

If you are breaking bolts like that you are over torquing them or there is some other issue. They only get torqued to 11 ft lbs. They don't have much of a job and the primary load is taken up by the sliders.

IIRC there is some sort of cover than can be installed on the sliders.

If you do go to the earlier setup I believe some calipers and rotors off of some year mustang will fit. But I don't recall the details of that.

As said previously if you want the earlier brakes (won't actually help performance unless you upgrade the rotors and calipers) you just need to replace the knuckle and other brake hardware, not the entire axle.

Infact, it might even make it worse as the OBD2 models had darn good brakes.

What rear brakes to you have? Seems to me that there are widths of brakes even on the OBDII models, but I could be mistaken.

The AW4 is good with mountains, and proper decent control will probably reduce your maintaince to a non-issue. Get a cooler on it if you want it to last a long time.

I don't believe a WJ knuckle and brake swap will give you more than you have now.

WB9YZU said:

Infact, it might even make it worse as the OBD2 models had darn good brakes.

I don't believe a WJ knuckle and brake swap will give you more than you have now.

Click to expand...

Those two statements right there prove how absolutely little you know.

A WJ brake swap will definitely help

rockclimber said:

Those two statements right there prove how absolutely little you know.

Click to expand...

Just have to love disrespectful kids.

WB9YZU said:

Just have to love disrespectful kids.

Click to expand...

Nominated.

I hate to brake this up, but.....

WB9YZU said:

Infact, it might even make it worse as the OBD2 models had darn good brakes.

What rear brakes to you have? Seems to me that there are widths of brakes even on the OBDII models, but I could be mistaken.

The AW4 is good with mountains, and proper decent control will probably reduce your maintaince to a non-issue. Get a cooler on it if you want it to last a long time.

I don't believe a WJ knuckle and brake swap will give you more than you have now.

Click to expand...

Sorry... but you are wrong and rockclimber is right.

Brake year splits I'm aware of:
89-90 AMC brakes to Chrysler new design, one piece knuckles (4x4 split this year)
92.0-92.5 AMC brakes to Chrysler new design using same knuckle/bearing as 4x4 (early side of split was spindle based w/ special rotors for 2wd)
91-92 Bendix to Chrysler ABS switchover (the only difference here is one works and one doesn't)
94-95 single diaphragm to double diaphragm booster change
96-97 booster/master design change but no significant difference in braking performance, it was simply a change from a different MC for ABS vs non ABS (95/96) to a common MC for both (97 and later)
99.0-99.5 unit bearing and corresponding rotor change, pad material change as well iirc, no significant braking differences

None of these have anything to do with OBD1 vs OBD2 and only one has a significant impact on braking ability, the single to double diaphragm booster change from 94 to 95.

And WJ brakes are a significant improvement, as well as improving steering angles.

As for what needs to match what, Tim_MN has it mostly right.

Hubs must match rotors.
Knuckles must match hubs and calipers across the AMC to Chrysler split, take note that the AMC to Chrysler split on 2wd is 92.0-92.5 which is later than most AMC to Chrysler splits. All Chrysler knuckles, 2wd or 4wd, are the same, and will fit all Chrysler unit bearings, though I'm not sure if the mounting hole for the ABS sensor is machined and tapped on non-ABS ones.
Calipers must match knuckles.

That's about it I think... corrections welcome.

Wow...!
I'm really thankful for the information... And there is a lot of it too !! Lol.
I'll get to work and line out the different options.
As far as size goes... It's a stock setup except for the rotors and pads that are upgraded ones and are supposed to cool better....I forget the manufacturer
So to all who took the valuable time to respond and share, I Thank You and wish you well.. I'll let you know how it goes... And I'll add the cooler.... Should have done it a long time ago..

Nice to see my fellow Caribbean man on the board. I am from Nevis, lived on Tortola for many years and now in the US for almost 20 years. My Ex and my daughter live on St. Croix.

The information on this board is second to none,...sometimes though you have to take some people's comment with a grain of salt. There is hardly a mile of paced road on the three islands that I have not driven. On STT and STJ, 3 (third gear) is a must. Going down hills, low gear may sometimes be necessary.

I have replaced my entire front brakes with an after market set in an effort to improve their effectiveness especially if you are using larger tires. I good quality rotor and pads will also go a long way to improving stopping ability. Most importantly, do not let the breaks overheat on those long hill descent.

One other thing that have not been mentioned (or did I miss it) is the rear breaks. They are notorious for poor performance. Remove the wheels and drums and have them checked,...every last piece and replace those pieces that are questionable. Many of us here on have replaced the rear drums with disks from a Grand Cherokee or an early Ford Explorer.

Hope this helps.

Gotta love the Internet, I looked up 30ft/lbs (DOH !) caliper torque because my FSM was in the garage, and I haven't used a torque wrench on calipers for years, I just know by feel when they are tight enough. I was going to guess 18 ft/lbs, but trusted some other dam website to be correct.

kastein said:

Sorry... but you are wrong and rockclimber is right.

Click to expand...

Ken, I appreciated your post. Well thought out and informative

My point was that increasing brake capacity up front won't help if the vehicle is not being driven to it's optimum capability.

Picture this: Instead of downshifting, you drag your brakes all the way down the hill to keep a desired decent rate. You will heat the brake pads, discs, overheat the caliper, and possibly boil fluid. In this case, he is putting divots in the caliper guides, snapping retaining bolts, burning out pads, and has reduced brake function. Will putting larger front brakes stop the driving style issues, or just move the system limit up a bit and change the system bias from the factory 60/40 to a more front heavy ratio?

The reason I brought up the rear brakes, and I mentioned OBDII because that is how I break out 96' Plus drivetrain; 8.25s all got the better 2.5" brakes when they started using that axle, and to my knowledge, though the YJ got the 2.5" rears on the D35, I don't know if the XJ did. Rear brakes must be in good condition, esp in extreme conditions. Bias is 60/40, and will be considerably more front heavy if the rear brakes are not up to par out back and will reduce overall braking capacity.

The post by Nevis talks about driving style on the island and recommended upgrading rear brakes. Upgrading the rears to disc is an awesome idea, will prevent many of the maintenance and performance issues with the drum brakes in extreme conditions, and will reduce stopping distance.

Finally...
Re: rockclimbers post, I disagree; being rude is not right.
"Those two statements right there prove how absolutely little you know." is not a discussion, or informative, it is an insult and based on other posts by that Member, was intended to be so.

And I am sorry for corking off in thread - I was wrong in doing so.
I apologize to all who read that.

Bahahahahaha

8.25s started in 91/92 or so and XJs use the same 9" drum brake shoes and drums from '90 through '01 (the 9" drums replaced the 10" AMC drums, 89 was the last year for 10" except on police packages iirc), so I'm not really sure where you are getting your brake system or axle info. The only 8.25 change in '96 was the mid year split from 27 to 29 spline. There is literally no performance difference in the brakes across the OBD1/2 split.

And front brakes do way more than rears, especially when stopping hard - the front squats down and the rear lifts up and you end up with very little actual braking in the back unless heavily loaded.

That being said, I upgraded to rear ZJ discs simply because I absolutely hate working on drums and the axle I got came with the rear brakes completely disassembled. And I lined up a full set of ZJ disc brake parts including almost brand new (could still see the crosshatching on the rotors and there was only the lightest of surface rust on them) rotors and shoes for $70 from the local pull-a-part. Made it a real no-brainer.

No I said "when they started using that axle". That means "all years" of XJ for the 8.25.

So you are saying that all XJs (D35 and 8.25) got the 9x2.5" brakes in 1990?

As far as the rear brakes, millions of race car drivers would disagree with your assessment of rear brakes. Brakes are not digital, but analog. The panic stop you describe is only one application of braking.

From what I've seen, yeah. As far as I can tell only the non c clip d35s got 10" drums, and they stopped with the non c clip axles in 89 or 90 iirc. Hell, I think the rear on my 88 MJ may be small drums, but I'm not sure... don't recall.

Yeah, brakes need to be balanced, but I believe the fronts do most of the stopping.