With all the options for the front, what’s the strongest front axle/IFS setup for a 89 1500?

[Burntoutaccountant]

Apparently I’m swapping in a 14 bolt 8 lug now that my rear end went boom after purchasing my first 89 Chevy truck. I need to address the front now.

My truck is pretty much being overbuilt for overlanding but also to be my daily while my bronco is my fun toy. I have a Dana 60 kingpin available but want to retain good road manners. Unfortunately the guy with the Dana wants $1500 so it’sa steep price.

Would a big brake kit suffice on the 8.5 front diff or is it really that weak? New to Chevy trucks so some input is appreciated.

 

[Nad_Yvalhosert]

Independent suspension means the differential is also independent of the brakes.
There are several upgrade threads involving 2500 calipers on 1500 trucks. Search for them and baske in the knowledge!
Why an 8 lug rear? Why not a 6-lug 2500 14 bolt? That way you'll retain the OE wheel bolt pattern.
Oh by the way, the front diff on the 1500s is an 8.25"

 

[Burntoutaccountant]

Independent suspension means the differential is also independent of the brakes.
There are several upgrade threads involving 2500 calipers on 1500 trucks. Search for them and baske in the knowledge!
Why an 8 lug rear? Why not a 6-lug 2500 14 bolt? That way you'll retain the OE wheel bolt pattern.
Oh by the way, the front diff on the 1500s is an 8.25"

Pretty much I want 8 lug for big stuff up front. If I can upgrade to 2500 brakes that should work. Should be a huge improvement. We were looking at it at my work and laughed at the tiny front rotors.

I put 8 lug k20 jb7 brakes on my bronco when frankensteining the front end together. Mated Chevy outer axles, backing plates, and brakes to a modified ford knuckle and it’s ttb Dana 44.

 

[Schurkey]

89 Chevy truck.

Would a big brake kit suffice on the 8.5 front diff or is it really that weak?

What do you have now? JN3 brakes? If so, those are the smallest, crappiest power brakes that GM put on the GMT400 trucks.

If I can upgrade to 2500 brakes that should work. Should be a huge improvement. We were looking at it at my work and laughed at the tiny front rotors.

WHICH "2500" brakes? The 8-lug 2500s might have 13" drums in the rear, and non-low-drag calipers with a fairly huge piston up front, as part of JB/JD/JN7 brake system. A 6-lug 2500 might have JN6 brakes, which are a significant upgrade from JN3 (front and rear, master and booster) and JN5 (at the rear. Same up front, same master, same booster.) The JN6 is still less-powerful than JN7, though.

My '88 K1500 came with JN3, but has been upgraded to JN6. Works well enough for me.

 

[Burntoutaccountant]

What do you have now? JN3 brakes? If so, those are the smallest, crappiest power brakes that GM put on the GMT400 trucks.


WHICH "2500" brakes? The 8-lug 2500s might have 13" drums in the rear, and non-low-drag calipers with a fairly huge piston up front, as part of JB/JD/JN7 brake system. A 6-lug 2500 might have JN6 brakes, which are a significant upgrade from JN3 (front and rear, master and booster) and JN5 (at the rear. Same up front, same master, same booster.) The JN6 is still less-powerful than JN7, though.

My '88 K1500 came with JN3, but has been upgraded to JN6. Works well enough for me.

What’s involved in the jn6 upgrade if you don’t mind me asking?

 

[Schurkey]

JN5 and JN6 are the same at the front, and have the same master cylinder and booster. JN5 (and JN3) have the horrible 254mm (10") leading-trailing shoe drum brakes, while JN6 uses the wonderful 11.x Duo-Servo rear drums.

JN3 has thinner front rotors, (and therefore different front hubs/bearings) smaller pistons in the calipers. A small-bore Quick Take-up master cylinder (1" instead of the JN5/6 1 1/8" bore QTU master) along with a tiny "pancake" vacuum brake booster. JN5/6 has a much bigger booster to go along with the bigger master cylinder.

If you have JN3 or JN5 brakes, the best single upgrade is to get the 11.x Duo-Servo rear drums. Upgrading the front of JN3 is important, but not as important as getting rid of the 254mm leading/trailing drums.

If you're swapping in an 8-lug rear axle, the rear brakes are now the least of your concerns assuming they're in good condition. (If they're the bigass 13" drums, you'll maybe have problems getting them to balance with the fronts. I guess that'd be a concern.)

My '88 K1500 had the rear axle swapped for a 6-lug 2500 unit because the crappy 10-bolt was worn-out. The bigger rear brakes were a bonus. Later on, I discovered I had a damaged steering knuckle--which broke the ball joint. Replacing the steering knuckle, I grabbed everything from an extended-cab which had the JN5 brakes. I didn't know there was a difference until I got the parts home and started swapping them onto my truck. That's when I figured-out that the extended cab "donor" had thicker rotors and bigger pistons. Had to go back to the Treasure Yard to get the bigger master 'n' booster to go with the thicker rotors and bigger calipers. From a certain perspective, my brake upgrade from JN3 to JN6 happened as a result of other issues, and a good bit of luck.

 

[Burntoutaccountant]

JN5 and JN6 are the same at the front, and have the same master cylinder and booster. JN5 (and JN3) have the horrible 254mm (10") leading-trailing shoe drum brakes, while JN6 uses the wonderful 11.x Duo-Servo rear drums.

JN3 has thinner front rotors, (and therefore different front hubs/bearings) smaller pistons in the calipers. A small-bore Quick Take-up master cylinder (1" instead of the JN5/6 1 1/8" bore QTU master) along with a tiny "pancake" vacuum brake booster. JN5/6 has a much bigger booster to go along with the bigger master cylinder.

If you have JN3 or JN5 brakes, the best single upgrade is to get the 11.x Duo-Servo rear drums. Upgrading the front of JN3 is important, but not as important as getting rid of the 254mm leading/trailing drums.

If you're swapping in an 8-lug rear axle, the rear brakes are now the least of your concerns assuming they're in good condition. (If they're the bigass 13" drums, you'll maybe have problems getting them to balance with the fronts. I guess that'd be a concern.)

Ended up finding a 6 lug 14 bolt. So I’m staying 6 lug. I figured I’d have to use a proportioning valve to get the brakes dialed in. Since it’sa daily I need to not go racecar build with it and the 8.25” front diff should be fine with a truetrac (if they make one).

So there is so much information I can’t figure out what is the right path. I do have jb3 front brakes. They are horrible. I want to upgrade to jb5/6. Do I need to change the spindles or can those be reused? That’s where I’m stuck. What years came standard with jb5/6 brakes? I think I saw later gmt400s having them standard and my truck having unique spindles.

 

[Schurkey]

1. There are no "spindles" on a 4WD. You have a steering knuckle and a hub/bearing assembly on each side. The steering knuckle is the same. The hub/bearing assembly is different between JN3 and JN5/6. I took the entire steering knuckle/hub/bearing pair from the donor truck, since I had a damaged steering knuckle to begin with.

What I grabbed from the Treasure Yard:

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JN5/6 left, JN3 right.

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Master cylinders are the same Quick Take-Up design, but with a 1/8 larger bore for the JN5/6 compared to the JN3.

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2. JN3/JB3 brakes were discontinued for 1992, perhaps. After that, the base power brake system was JN5 or JB5. I think only the regular-cab pickups got JN/JB3. Extended-cab trucks got the JN/JB5. So use an extended-cab pickup, a newer regular-cab pickup, or a Suburban as a donor.

3. If you're using the 6-lug 2500 axle (be sure it came from a K2500, not a C2500--they're different widths) then you'll have the 11.x Duo-Servo rear brakes, and when you upgrade the front, master, and booster, you'll have the equivalent to JN6 just like my '88.

4. There's no limited-slip option for the 8.25 front differential that I know of. I've heard rumors that some Dodge limited-slip differential can be crammed in there, and there may be aftermarket options I don't know about.

5. You're upgrading the rear brakes via the axle swap. You upgrade the front brakes, the master cylinder, and booster to JN5/6 spec, you have a "matched set" front and rear. No problem with proportioning valve--should work as-is.

 

[Hipster]

There's not a whole lot of love for the 1500 front diff. The larger one bolts in different, different width, different length cv axles, 2500 uca's don't bolt on a 1500 frame, etc. The 8.25 is not known to hold up for extreme off road. No lunchbox lockers or LSD's that I'm aware of. Quite a few have tried but none have ever come back to say they completed the bigger diff swap or have been remotely successful that I'm aware of. Most serious guys skip the lift kits and go SAS.

 

[b454rat]

I don’t have a 1500 (other than my Yukon) but I’m putting and IFS lift on my 99, and if where to do it again, screw the IFS n go SAS. Such a PITA taking all thst crap off just to put it back on. Get the hot wrench out n torch all the mounts n brackets off, drill some holes in the frame, mount the brackets n swing an axle under it. I will be SAS’n the Yukon once other truck is done….