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Super Moderator
13,734 Posts
Discussion Starter · #1 · (Edited)
The community here at urges you to please use caution and seek professional assistance when performing modifications to your vehicle. Before attempting any modification it is advised that you refer to your Colorado or Canyon service manual or contact a certified mechanic as not all GMT355 trucks are the same. The staff and the associated members are in no way responsible for any damages, injuries or other harm inflicted to your vehicle or yourself which may result in attempting these modifications. The posts and content presented on this site reflect in no way the views of or it’s ownership.

A 355nation How To presented by

Project Name
How-to: Low Profile Transmission Crossmember Installation

Project Description
A low profile or high ground-clearance transmission crossmember improves ground clearance by about two inches, compared to the stock crossmember.

On a ZQ8 truck, the cross member is about 5-1/4" above the ground. If the ZQ8 truck is heavily loaded, or lowered, then the crossmember will be even closer to the ground, and can contact bumps in the road, or speed bumps in parking lots.

Skill Level

Project Vehicle
Make: Chevrolet
Model: Colorado
Year: 2009
Engine: 5.3L

Notes: These picture and procedures show a Belltech #6963 being installed on a 2007.
They were NOT taken of my JTR install. I'll update the pics once I get mine installed.

Recommended Tools
  • Blocks and Wheel chocks
  • Properly rated floor jacks and support stands
  • Ratcheting Socket Wrench (15mm & 18mm)
  • Combination Wrench set (15mm & 18mm)
  • Safety Glasses
  • Abrasive cutting wheel
  • Sawzall
  • Air Ratchet
  • Torque wrench 10-75lb.ft range
  • White marking pen
  • Plasma Cutter (optional)

Parts List

Project Time
4-5 hours.. depending on your cutting tool. Goes pretty fast with a plasma cutter and a lift.

Project Cost
The JTR Low-Profile crossmember was $175 shipped.

I opted to powdercoat mine for an additional $20. POR-15 Chassis Coat Paint or Line-X are also good options.

  1. Open the hardware kit and remove all the contents. Refer to the parts list to verify all parts are present.

  2. Park the vehicle on a smooth, level concrete / asphalt surface and put the vehicle in gear or park. Place a block in front of and behind the front wheels. Jack up the rear of the vehicle and place the jack stands in the factory specified locations. Refer to the Owner’s Manual.

  3. Using a properly rated floor jack, lift the front wheels of the vehicle off the ground. Place the support stands, rated for the vehicle’s weight in the factory specified locations. Refer to the vehicle Owner’s Manual. Prior to lowering the vehicle onto the stands, make sure the supports will securely contact the chassis.

  4. Slowly lower the vehicle onto the stands and, before placing the vehicle’s entire weight on them, again check that they properly and securely contact the chassis as described above. Check for possible interference with any lines, wires, cables, or other easily damaged components.


Prior to removing the O.E.M. Cross-member, support the rear of the transmission housing with an adjustable jack stand.

  1. Using an 18mm and 15mm wrench or socket head, remove the top mount hardware that attaches the O.E.M. Cross-member to the underside frame chassis.

  2. Using an 18mm wrench or socket head, remove the four outer O.E.M. mounting bolts.

  3. Using an 18mm wrench or socket head, remove the two center mount hardware.

  4. Once all the hardware has been removed, carefully remove the O.E.M. Cross-member from its original position and set aside.

  1. To gain access to the passenger side bracket, the muffler will need to be removed. This is the section the catalytic converter is attached to. Three bolts mount the engine end (front end), with two bolts mounting up to the muffler end (rear end).

  2. First, disconnect the electrical wiring connector.

    NOTE: Use of a pneumatic ratchet can be used if accessible.

  3. Using a 15mm wrench or ratchet with a 15mm socket head, remove the mounting bolts (front end) completely.

  4. Using a 15mm wrench or ratchet with a 15mm socket head, remove the mounting nuts (rear end) completely.

  5. Remove the muffler (catalytic converter) section from the vehicle.

  1. With a white marking pen, mark the areas where the cuts will be made

  2. The horizontal cut-line is measured at 35mm (1.37in), from the top of the lip of the bracket.

  3. Mark both brackets.

  4. To avoid damage to any brake or electrical lines, we recommend moving them slightly out of the way. Disengage the lines from the clips and tie aside out of the way.

  5. Using a cutting wheel, begin cutting the bracket where you had marked.

  6. Remove the discarded bracket. Do this to both sides.

  7. Once you have removed the O.E.M. Cross-member brackets, grind the remaining pieces left on the chassis, smooth. For a finished look, you may spray the newly cut areas, black.

  1. Holding the new cross-member up to the mounting points, finger-tight the mount hardware only.

  2. With the new cross-member up in its position, install the center mount hardware, but do not fully tighten.

  3. Using a 18mm wrench or a ratchet with a 18mm socket head, tighten the outer mount hardware. Once that is done, tighten the center mount hardware.

  4. Torque all mounting hardware to manufacturer’s specs.


If for any reason the muffler pipe actually touches the top of the new cross-member, once it has been installed, follow the steps below to rectify the problem.

  1. Install the O.E.M. muffler (catalytic converter section) back up into its original position. This will be located above the new cross-member. Attach all the respective mounting hardware and finger-tight only.

  2. Once you begin tightening the hardware, keep pressure on the muffler, pushing it upward to the underside of the vehicle cab. Torque the mount hardware (while still pushing upward) to the manufacturer’s specs.

  3. There should be a minimum clearance of 3/8” between the top of the new cross-member to the muffler.


  1. All hardware being fastened to the vehicle’s original fastening points should be torqued to the proper specifications. To prevent chassis damage, never over-torque the hardware.

  2. Check that all components and fasteners have been properly installed, tightened and torqued.

  3. Check brake hoses and other components for any possible interference.

  4. Lift the vehicle and remove the support stands. Carefully lower the vehicle to the ground.

  5. Immediately test-drive the vehicle in a remote location so that you can become accustomed to the revised driving characteristics and handling. Be aware that the vehicle will handle substantially different now that it has been modified.

  6. Installation is complete. Check all of the hardware and re-torque at intervals for the first 10, 100, 1000 miles.

US Army 19yrs and ......
45,275 Posts
Excellent write up for sure!

I did not personally remove any of the exhaust system though.

Nation Affiliate
351 Posts
Great write up! Will be installing my lo pro member in a week or two. I'm thinking that I will have to take off my exhaust because my crossmember sit in between the frame rails. Not un the bottom side of the frame

Super Moderator
13,734 Posts
Discussion Starter · #8 · (Edited)
I had the truck in the shop this morning getting my new JTR low-profile transmission cross member installed. I was just me and the owner in the shop, so I was able to take a bunch of pics.

Before: Factory Transmission Cross Member

After: JTR Transmission Cross Member

JTR Low Profile Transmission Cross Member

After a trip to the Powered Coater...

Getting her up in the air..

Factory Cross Member Removed..

Cutting the Factory Mounts..

Factory Frame Mounts cut off..

Factory Frame Mounts Removed..

Cleaning up the rough edges...

Painted the exposed metal chassis black.

Bolting it up..

We used a couple of wire ties to secure the rubber vent tube for the tranmission.

We had to fabricate a bracket to support the fuel lines.

Finish and back home... Looks so much better.

508 Posts
Excellent write up for sure!

I did not personally remove any of the exhaust system though.
:yeahthat: i don't think it's really necessary to remove the exhaust
Just my $0.02 from installing mine.

I had to remove the exhaust section because I couldn't use the Sawzall or grinder to get the OEM mounts cut off without moving the exhaust. I'm sure I wouldn't have had to remove it if I'd had the truck lifted on a hoist but with only jackstand clearance under the truck I couldn't get the tools at the areas to take them off.

Excellent write up RSHADD. :thumbup:

Super Moderator
13,734 Posts
Discussion Starter · #12 · (Edited)
i noticed you said at one step that you used buttonhead bolts but another later step u said to use a 18mm socket.... looks like the pics show a hex style button head. can u please clarify. mine came in today.
Either will work. The button heads are less prone to catch on something and shear off.

Member's Technical crew
4,308 Posts
Hey guys would anyone be kind enough to post up dimensions? Since mine will be custom I only need the main cross member not the mount. Goanna price it out to see if a local metal shop can break and shear it for me. Looks like 3/8" think? 5-6"wide?? 45 inches long? 1.25" break up on either side?

Super Moderator
13,734 Posts
Discussion Starter · #20 ·
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