What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[89Suburban]

ugh, when I test fit I didn't think the thick one would even fit. sounds like I'll have to force it and hope.


man it's such a long story with hybrid brakes, it's literally the most complicated system on the truck. think if you needed to design fly by wire brakes but 20 years before fly by wire brakes were a thing, so it's completely mechanical. the pedal doesn't actually send fluid to the calipers. that's all done by a 2000psi motor and accumulator. but to make the pedal feel normal, there's a whole brake feel cyl section. and then as a back up if the whole nonsense fails the pedal goes low enough that it bypassed all that and actually works like normal brakes sending fluid from master to caliper. throw in you charge and batteries by regen, and that needs to feel seamless as well. so that transition from regen to slowing down below regen speeds. the back brakes need to kick back in. all without feeling it. oh yeah, there's no adjustments for it. it's just gotta be perfect or you start replacing parts. parts thst are all obsolete and discontinued at this point.


but yes, gm techs have always been clueless in general but more so specifically gm hybrids and electrics. which is sad because gm was away ahead of the curve on all of it. so far ahead they gave up on it all before it became popular enough to be profitable.
they needed a tsb to tell them how to bleed the breaks and that requires a full 30psi with fluid on top while running the automatic brake bleed with the tech 2 with 2 people.

I mainly want to flush the fluid before before it causes me trouble but also be nice not to break it along with way haha.

I keep forgetting you have a hybrid

 

[j91z28d1]

I keep forgetting you have a hybrid

it's dumb but mildly interesting in a nerdy kinda way where you like weird things that make your life more difficult.

things like balance charging hybrid cells

 

[Tonyrodz]

ugh, when I test fit I didn't think the thick one would even fit. sounds like I'll have to force it and hope.


man it's such a long story with hybrid brakes, it's literally the most complicated system on the truck. think if you needed to design fly by wire brakes but 20 years before fly by wire brakes were a thing, so it's completely mechanical. the pedal doesn't actually send fluid to the calipers. that's all done by a 2000psi motor and accumulator. but to make the pedal feel normal, there's a whole brake feel cyl section. and then as a back up if the whole nonsense fails the pedal goes low enough that it bypassed all that and actually works like normal brakes sending fluid from master to caliper. throw in you charge and batteries by regen, and that needs to feel seamless as well. so that transition from regen to slowing down below regen speeds. the back brakes need to kick back in. all without feeling it. oh yeah, there's no adjustments for it. it's just gotta be perfect or you start replacing parts. parts thst are all obsolete and discontinued at this point.


but yes, gm techs have always been clueless in general but more so specifically gm hybrids and electrics. which is sad because gm was away ahead of the curve on all of it. so far ahead they gave up on it all before it became popular enough to be profitable.
they needed a tsb to tell them how to bleed the breaks and that requires a full 30psi with fluid on top while running the automatic brake bleed with the tech 2 with 2 people.

I mainly want to flush the fluid before before it causes me trouble but also be nice not to break it along with way haha.

Sounds similar to the Powermaster brake setup in the 86/87 Grand Nationals. Had an accumulater with a brake bowl setup. Worked great--when it worked. Mine went out while driving on rte 80.

 

[j91z28d1]

Sounds similar to the ****** brake setup in the 87/88 Grand Nationals. Had an accumulater with a brake bowl setup. Worked great--when it worked. Mine went out while driving on rte 80.

I'll have to look it up. I'm guessing it was a hyboboost because of the turbo run off the power steering? I'm curious, seems gm has always like over complicated things. even thou I'd definitely take a gn right now haha. always liked the GN powered trans ams growing up, except I've always kinda been a manual transmission guy.

some old Astro vans had a hydro boost for some reason, I guess it helped stop in the days of tiny brakes and bad pads tech haha. I remember people would swap them into 3rd gens and say how great it felt.

 

[Tonyrodz]

I'll have to look it up. I'm guessing it was a hyboboost because of the turbo run off the power steering? I'm curious, seems gm has always like over complicated things. even thou I'd definitely take a gn right now haha. always liked the GN powered trans ams growing up, except I've always kinda been a manual transmission guy.

some old Astro vans had a hydro boost for some reason, I guess it helped stop in the days of tiny brakes and bad pads tech haha. I remember people would swap them into 3rd gens and say how great it felt.

The 84-85's had the hydro boost setups. The 86-87's used a big electrical motor deal that was mounted under the master cylinder iirc. The hydro boost setup was much better, and more reliable.

 

[Grady_Wilson]

Getting ready to get back on the road.
Stayed overnight in Utah, Yukon got warmer than I liked pulling long grades in 115* heat.
Would sometimes get to the 3/4 matk but would come right back down very quickly. May have to invest in a radiator just to see if that makes any difference.
Didn't get warm at all in temps under 100* pulling grades.
I've got the biggest trailer U Haul rents behind me and it's packed so I know there is weight behind me, I can feel it.
Though it tows nicely and will do 70mph no problem, feels solid.
Calif gas gave me 10mpg while out of state gas is giving me 12.7mpg.

 

[Just Fishing]

I did it yesterday morning, but the new ARP bolt set came at about 5am.
I swapped it for the new one and checked the other bolts.
All tight except for the front two bolts on the passenger side.

Weird, and I know I torqued that shit, the paint marker on the other ones are still there.


Oh well, now I have spares.

 

[89Suburban]

I did it yesterday morning, but the new ARP bolt set came at about 5am.
I swapped it for the new one and checked the other bolts.
All tight except for the front two bolts on the passenger side.

Weird, and I know I torqued that shit, the paint marker on the other ones are still there.


Oh well, now I have spares.

Were the old one ARPS?

 

[Just Fishing]

Were the old one ARPS?

Yes sir.
I only lost a single, but still it's weird that only two came loose.

 

[Runfor5]

It's the little things my license plate bulb covers were super faded. Ordered 2 of these off AMZN, they even came with new screws and bulbs not shown in listing photo! From a auto parts place in Nevada, TX. Arrived bubble wrapped, no GM box, but the markings are the same on the plastic as the ones I took off. For just $40 total, 10/10 would recommend.

https://www.amazon.com/dp/B00GUD9BOM?psc=1&ref=ppx_yo2ov_dt_b_product_details