NEED HELP Extenses and Adjustable Control Arms

scandelario90

Newbie
Original poster
Jun 5, 2021
4
LA
So I've been helping my buddy build up his trailblazer and since i don't live near by to measure this and as a group I would like to share and confirm some of the things I've been tinkering with.

Current lift is the Z71 tahoe springs and a 1 Inch spring spacer.

As of now i see the Spohn Rear Control arms as the go to fix for the pinnion angle and recentering the rear wheels.
These control arms look street worthy but not offroad worthy.

From what I've read the stock Rear control arms are:
  • 17.5 inches eye to eye upper
  • 21 inches eye to eye lower
  • 2.625 (5/8th) inches wide at the bushing (ALL ENDS)
  • M14 or 9/16th's mounting hardware (ALL ENDS)

I am looking for the circumference of the end, from what I am seeing, a lot of control arms are kind of generic in the mounting options. If so I have found some possible candidate for use.
  • -Adjustable Lower Rear Control Arm from a Jeep JK for 0-4 inch lift can be used (Freedom Offroad USA; SKU - FO-J703RL-ADJ)
  • a Stock JKU Rear Lower Control Arm is 19.75 Inches so a control arm adjustable for a lift should cover the 1.25 difference in length. I HOPE, or a control arm covering a different set of length could cover the range we are looking for in a lifted trailblazer

  • - Adjustable Upper Front Control Arm from a RAM 2500/3500 (03-07) IF the Bushing on one end can be changed to Accommodate the M14 (9/16ths) hardware. (Freedom Offroad USA; SKU FO-D701F-ADJ)
  • Adjustable to provide proper geometry for vehicles lifted 1-6" (17.5" at shortest and 20.4" fully extended center to center measurements)

Concerns:
the Upper control arm might have a slight angle on it, A johnny joint might help. Need to find out what those Specs are.
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,275
Tampa Bay Area
You might be looking at the WRONG Rear Suspension Component(s) as being at issue here:

(1) Install the Identical Rear Suspension Gear Items.
(2) Test Drive the Vehicle.
(3) If the Truck "Dog Tracks" like THIS one does...


(4) Follow on with what is being recommended HERE:


(5) Or Follow on what is recommended HERE for "Dog Tracking" Lifted Trucks:


(6) Ultimately... a Pro Shop Alignment may be required.
 

scandelario90

Newbie
Original poster
Jun 5, 2021
4
LA
Its not crab walking. Its definitely aligned as it can be at the moment. None of what you mentioned are the concerns I have. As lift is added the position of the axle is shifted slightly forward. That in conjunction with larger wheels can create some rubbing while articulating and will certainly cause some issue if sliders are installed.

Also the axle to transmission relation has changed. The angle of the pinon is expected to be off. This causes excess strain on the rest of the drivetrain. the G80 is a known weak LSD (E-lockers will likely replace this eventually) and the 4L60-E transmission, kind of a known dud for GM.

its very common for full lift kits of other vehicles to include adjustable extended control arms to correct these issues as you increase the lift height.

obviously as stated, trailblazers just don't have that after market support. The only adjustable suspension parts I have found still in production Sept 2022 that are a sure drop and go component are the SPOHN racing control arms. they do not look up to the rigours of any long term offroading. my guess is they were designed with the SS trailblazer in mind.

short of Fabricating control arms from scratch, the option I am trying to explore is borrowing after market parts from another vehicle.

If I do end up discovering usable parts. I will share what ever information I find.
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,275
Tampa Bay Area
Okeedoke... And don't forget to ask your "Buddy" to Join Us as a Member Here at GMT Nation and show some images of his ride. It would be nice to see his participation in this Thread and give us his opinions, too on such a rare topic as him Building Up a True Off - Road Trailblazer.
 

scandelario90

Newbie
Original poster
Jun 5, 2021
4
LA
My Jeep is in the background. I have the same control arm issue. My issue isnt finding the part, its finding the budget hahaha. he already trimmed the front wheel wells. the rear isnt as bad but why not just correct the rear suspension geometry if we can. those chevy 8.6/8.5 axles are pretty good. i recently found out that aftermarket yukon springs will work on the rear.

the goal is to get it through Cleghorn in San Bernandino or to atleast outperform this other newer tacoma in the group haha.

for some reference this is and overview of the trail.
 

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