99 Suburban LT K1500 - Slow build

[99'Subourbon]

35s (technically they measure 34.5").

But yet, I'm still holding onto some hope that getting a retune will fix some of this winded feeling. It seriously felt like it had more go with the 3.73s and the same tires when I drove it to the valley to get the gears swap.

It almost feels like prior to having headers and an exhaust, like it can't breath/being held back.

 

[98sierra4x4]

Did they swap the right grears in?


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[99'Subourbon]

Did they swap the right grears in?


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Havent checked yet but my speedo is way off now, where as it was dead on before after putting on the 35's with 3.73s. When it reads 80 its actually about 65 mph, and I run 2050~ rpms. When it reads 93mph, its actually about 75 mph and its turn 2350~ rpm. That, and the ABS light comes on now after each start as soon as I get up to about 15-20 mph.

I haven't yet, but I intend to jack up the rear, mark the driveshaft, and turn the tires 1 full rotation - counting how many times the driveshaft turns will tell me what gears I have.

 

[slowburb]

This is a bit puzzling to me, too. Did you ever have the speedo calibrated for the 35"/3.73:1 combination? Do you have a higher or lower rpm crusiing at 65?

 

[99'Subourbon]

This is a bit puzzling to me, too. Did you ever have the speedo calibrated for the 35"/3.73:1 combination? Do you have a higher or lower rpm crusiing at 65?

I had the speedo corrected for the 33s I had originally, when I got my tune (to go along with the 3.73s). It ended up being ~5 off after the correction. Then I put on the 35s, and it was dead on (not sure how that worked out, but it did) with the 3.73s. And now here we are, with it being like 12-18 off after about 55 mph, with the 4.56s with 35s.

The rpm's were lower before the gear changes.. I want to say about 1800 at 65mph.

Here's why I think it may be tune related. It shifts into the next gear much sooner now, or so it seems. If I get on it, it'll wind way up before it shifts down to really start accelerating. Never did that before the swap - it would just downshift and go. Also, it wants to engine break all the time now. Uphill, downhill, slow, fast... doesn't matter what, if I get off the gas, it starts engine breaking. Something it seldom did before, only when going downhill at highway speeds.

The tune, I am assuming, was setup specifically for my gear size, tire size, and shift points. Since that is all off now, it just doesn't know how to run.

 

[slowburb]

There was a night and day difference in my truck going from 33's/3.73 gears to 33's/4.56 gears. Very obvious low speed torque improvement and very obvious highway cruising rpm increase.

 

[SwampHound]

I had the speedo corrected for the 33s I had originally, when I got my tune (to go along with the 3.73s). It ended up being ~5 off after the correction. Then I put on the 35s, and it was dead on (not sure how that worked out, but it did) with the 3.73s. And now here we are, with it being like 12-18 off after about 55 mph, with the 4.56s with 35s.

The rpm's were lower before the gear changes.. I want to say about 1800 at 65mph.

Here's why I think it may be tune related. It shifts into the next gear much sooner now, or so it seems. If I get on it, it'll wind way up before it shifts down to really start accelerating. Never did that before the swap - it would just downshift and go. Also, it wants to engine break all the time now. Uphill, downhill, slow, fast... doesn't matter what, if I get off the gas, it starts engine breaking. Something it seldom did before, only when going downhill at highway speeds.

The tune, I am assuming, was setup specifically for my gear size, tire size, and shift points. Since that is all off now, it just doesn't know how to run.

Definitely the tune. IIRC black bear offers free retunes for life. I would get it properly adjusted for the latest upgrades.

 

[99'Subourbon]

Definitely the tune. IIRC black bear offers free retunes for life. I would get it properly adjusted for the latest upgrades.

Yeah, they do - I'm in contact with them atm, should have my PCM sent out today or tomorrow, and hope that gets me feeling better about the whole thing.

You ever get your alignment straitened out?

 

[SwampHound]

Yeah, they do - I'm in contact with them atm, should have my PCM sent out today or tomorrow, and hope that gets me feeling better about the whole thing.

You ever get your alignment straitened out?

Nope. Truck needs balljoints first. Probably won't get done until next week if the money comes through

 

[99'Subourbon]

Whelp - no news is not good news, these days.

I've been ill with mycoplasma pneumonia for 3 weeks, money gone that I couldn't afford.

and now, I'm pretty sure my tranny is toast.
It is revving high, and barely moving, then starts to move, and slams into 2nd, then does the same thing for 3rd - won't go into OD. Its at about 5K rpm doing 30mph in 3rd.
On top of that, or DD envoy, is reading 0 oil pressure, and sounds like it. Hoping its just the sensor, or a clogged oil valve lifter filter; googling shows that to be a common issue.

...and right before Christmas for our kids. I'd take it in stride any other time of the year, but when interjects into my kids Christmas, boy is it depressing.