Offroad Trailblazers and Envoys

Trailblazer EXT power steering pump on SWB model.

Trailblazer and Envoy related, but not off-road related...

by v7guy » Fri Jul 05, 2013 2:48 pm

Since my steering has been rather noisy for quite some time, I was poking around looking at this and that. I noticed there's a different part number for the EXT power steering pump. I assume it would up the pressure/volume a bit to deal with the added weight.
I also noticed the steering rack has different part numbers between the EXT and the SWB trucks.

Maybe there's a small chance the SWB rack wouldn't care for the pump from the EXT... I dunno. Searching around doesn't show anything other than the standard replacement.

Has anyone tried this out?
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by The Roadie » Fri Jul 05, 2013 3:16 pm

The only difference in the pump is the diameter of the pulley. Smaller on the EXT to generate more pressure at idle.
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by v7guy » Fri Jul 05, 2013 3:25 pm

well that's disappointing.
That's what I get for going off of rockauto pictures and descriptions. None of them show a pulley, so I ass u me there was a pump difference given different part numbers and prices for the aftermarket brand and the ACDelco brand. Then GMpartsdirect listed 2 different parts with the ext version being double the price.
The different part numbers for the rack made me further suspect I was barking up a new tree.
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by blacksheep » Fri Jul 05, 2013 10:13 pm

I could try to get some pics from my EXT for comparison if interested
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by v7guy » Sat Jul 06, 2013 2:49 am

from all the pics I've seen they look identical...
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by Blazintrails03 » Sat Jul 06, 2013 11:55 am

There are now 3 TB's in my family. My 03 and my mother and sisters almost identical 07's. All 3 have made power steering whining noises at one point. With a simple turkey baster to suck the fluid out and filling it back up the noises have gone away to date and not returned. For good measure I sucked it out and filled it, went lock to lock with the wheel a couple of times, and sucked it out and filled it again. I wouldn't recommend a flush since it isn't a true flush and the method I used achieves the same results without the pneumatic extractor of a BG flush machine
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by Shdwdrgn » Mon Sep 16, 2013 11:13 am

So is it possible to swap in a smaller pulley on the SWB and get a lighter-touch steering? Anyone know if the pulley is a press-on or bolt-on style? I really miss the feather-light steering from my old car, would love to improve the response on my truck.
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by fishsticks » Mon Sep 16, 2013 11:52 am

Press on. Rent the puller from your local parts store. It's an easy job.
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by The Roadie » Mon Sep 16, 2013 11:56 am

Heating the pulley helps reduce the force. Before putting a pulley on the new pump for a friend's TB, I put the pulley in the oven at 250 for 15 minutes. Slid on easily.
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by Shdwdrgn » Mon Sep 16, 2013 12:06 pm

Sounds easy enough, and I have a small puller that might fit it. So has anyone ever actually tried this mod, and if so, did it make a difference?
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by dirty anton » Mon Oct 14, 2013 7:18 am

http://westtexasoffroad.homestead.com/p ... ering.html Like Stated I Would Try In small Steps Till You Get What You Want. This Is Geared Toward A Hydro Assist Setup But Some Of The Steps Here And A Smaller Pully May Get You There.
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by mikekey » Tue Nov 26, 2013 2:06 pm

Yes, I'm revving and older thread. Has anyone actually switched to a smaller pulley or a better pump?
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by ErikSS » Tue Nov 26, 2013 6:03 pm

I'm curious if my SS pump is the same as EXT, standard swb, or if its different yet. Maybe this hotel will have working WiFi.
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by Shdwdrgn » Tue Dec 12, 2017 4:04 pm

Time to resurrect this thread again since I found out today a failing pump is the most likely culprit for recent steering problems (no power at idle once the engine heats up), although the turkey-baster idea above seems easy enough to try since the problem started immediately after a recent steering rack replacement...

So it's been four years, has anyone actually tried changing the pulley diameter yet? How about using the EXT part number steering pump in a SWB vehicle? Any difference?

Also while I'm at it, the mechanic told me the pulley on these is plastic and requires a fork-type tool to pull them, but considering it is a press-fit and the above comments talking about putting the pulley in the oven at 250 degrees, now I'm wondering what I'll actually be dealing with in replacement parts? If I do have to get a new pump, I'm going to get a new pulley as well and not bother trying to remove the original one.

[EDIT] I found the following Dorman pulleys:
Dorman 300-137 -- 5.224" diameter, Fits EXT
Dorman 300-138 -- 6.14" diameter, Fits SWB

That's a pretty significant difference in diameter so I'm guessing I will need to also change my serpentine belt (not a bad idea anyway, I think I still have the factory belt!) so I'll also try to dig up some numbers on the belt lengths and see if an EXT belt looks like it will fit. Since the belt wraps about half way around the pulley, I'm calculating a difference in belt length of about 1.4" shorter.

[EDIT 2] Yeah there's definitely a difference in the belts. 91.54" for the SWB and 90.55" for the EXT. That seems suitable for the difference in the power steering pulley. Seems like I have a plan for the parts now, will just wait awhile and see if anyone else has done this mod...
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by Shdwdrgn » Sun Dec 17, 2017 5:04 pm

Per the advice above by Blazintrails03, I sucked as much fluid out of the reservoir as I could, which looked pretty dark. Wouldn't surprise me if that too was factory-original. Refilled with new fluid, drove it a bit, but still getting the same noises and resistance. I'll give it a couple more days just to see if anything settles out of the system, but at this point I'm pretty sure I'll be replacing the pump soon. Of course we have a big snow storm and blistering cold weather predicted by the end of the week, but I doubt I'd have all the parts on hand before then anyway.
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by DirtyBacon04 » Sun Dec 24, 2017 1:46 pm

So if I'm reading this right, the pumps are the same, and the difference in part number is attributed solely to the size of the pulley?

So, Shdwdrgn, are you replacing the pump with a SWB p/n and putting on the smaller pulley and belt?
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by Shdwdrgn » Sun Dec 24, 2017 2:02 pm

No, the other way around... I have a SWB model and I'm replacing it with the EXT version parts. From what I could find of part numbers, the pulley on the SWB is 6.14" diameter while the pulley on the EXT is 5.224". I ordered the pulley online (Dorman brand) last week and I'm going to head to the parts store today to get the new pump and belt ordered. I don't know if there's any actual difference in the pumps but I plan on getting the EXT part number, just in case it's been tweaked to better handle the higher RPMs.

Not seeing anything promising in the weather forecast though so it may be a few weeks before I get them swapped out. In the meantime the old pump is continuing to get louder. Not horribly, but it's enough to bug *me*. I want to make the swap on the street because I just really don't want all that fluid all over my garage floor.
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by Shdwdrgn » Fri Dec 29, 2017 7:57 pm

Project complete! So first the bad news -- the steering *may* be slightly lighter to the touch, but it's such a subtle difference that I can't tell if it's not just wishful thinking. If you're planning on changing out your power steering pump and/or pulley just for easier steering, this is by no means worth the time or money involved to make the switch! Disappointing, to say the least.

As for the actual process, and for anyone else who may pass through before they do their own PS swap... The process itself isn't that difficult, just time-consuming. To begin, remove the serpentine belt and pull out the air cleaner and washer fluid reservoir. Note there are three electrical plugs on the washer reservoir that should be disconnected, then you can lay the tank across the intake with the washer lines still attached. This will give you a wide-open space to work on the power steering pump.

As for the pump itself, as mentioned above use a turkey baster or similar to remove as much fluid as you can from the pump. There is a depression inside the reservoir on the passenger side towards the front that is an inch deeper than everywhere else, so you can get almost all the fluid removed. On the rear of the passenger side is a rubber return line with a simple clamp that can be removed. Next you want to remove the pressure line from the bottom side -- I used a 5/8" wrench but it might actually be a 16mm? Use a small can underneath the pump to catch whatever fluid comes out from the lines. There is a wire clamp on the back side of the reservoir which is a press-fit, just use some needle-nose pliers to pull it straight out and the clamp can be re-used on the new pump. Finally, there are three bolts holding the front of the pump to the engine block. Access these with a 13mm socket through the holes in the pulley, then remove the pump.

To prepare the new pump and pulley I iced the pump shaft and heated the pulley in the oven at 250F for about 20 minutes, then tapped it onto the pump shaft. Here's where I ran into the only problem... I picked up a Dorman pulley for an EXT, part # 300-137, which is just over 5" diameter, a full inch smaller than the SWB pulley. Unfortunately the Dorman part does not have the center hub in the correct position, or maybe the mounting on the EXT is just that different. When I put the pulley on facing the same direction as the original equipment, it was too far back by about half the width of the belt. If I had simply pulled the pulley back out to correct alignment, less than half of it would have still been on the pump shaft. So I pulled the pulley off completely, heated it in the over again, and then tapped it on backwards. I tapped it down as far as it would go without binding against the body of the pump, but when I checked the belt alignment it was still out too far. I fixed this by adding a thick lockwasher between the mounting bracket and the pump on all three screws. Now this will become quite a nuisance the next time I have to remove the pump, but it got the belt lined up exactly, and everything appears to be solid. Keep in mind if you are changing to the smaller EXT pulley, you will also need to replace the serpentine belt with a shorter EXT model.

Re-attach both fluid lines to the pump after tightening the three bolts. Then put the serpentine belt back on, fill the reservoir with new fluid, and start the vehicle. Turn the steering slowly back and forth all the way from one end to the other to get any air bubbles out of the lines, then shut off the engine and re-check the fluid level. Visually verify the belt alignment with the shiny spot on the idler pulley to make sure everything looks right, then reassemble the washer fluid reservoir and air cleaner. And you should be done!

In my case, the power steering pump was starting to go out and the serpentine belt has a minimum of 80k miles on it (it may actually be OEM), so I had to replace much of this anyway. After driving a few miles around town the air has worked out of the lines and the new pump is perfectly quiet. I'll check the belt again in a few days to confirm there is no wear from the new pulley being out of alignment, but otherwise I don't expect to need to do this again. I really lucked out because we've had some bitter-cold weather for the past week, then it got up to 60 today... and it will be dropping back into the 30's tomorrow and into the teens by Monday. Hopefully that's the last work I'll need to do before Spring!
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