First long trip... got problems. Not happy.

[OrangeCrush]

Okay, got back to NC from Fla. late last night. This is my first trip with the lift kit. I wasn't sure after installing the 4.56 gears if they would make up for the 38" taller tires.

First, I am truly disappointed in the performance. I installed the Volant air intake, 4.56 gears, Magnaflow exhaust and the SuperChip's programmer. I wasn't expecting seat of your pants performance difference but was hoping for something...anything.

The entire 1200 mile trip, I averaged 10.0 mpg. I was running 80-85 down there for the most part and stayed under 80 mph all the way back.
I realize that the gas mileage drops at speeds over 55 but I thought I'd at least average 12'ish mpg.

Secondly, I didn't notice on the way down but on the way up, I COULDN'T drive over 80mph. I'd get a terrible vibration. I don't think it was anything to do with tire balancing as a)usually you can feel it in the steering wheel fairly easily. and b)if you do have a tire out of balance, it's not normally in the 80mph range and if you increase the speed by 5-10mph, the wobble goes away.

My vibration felt in the drivetrain and stayed with me until I hit 95mph. I don't know if it would have gone away at a higher speed but bad tire balancing usually goes away 5-10mph faster.

Has anyone using the Fabtech kit had a vibration problem from their front driveshaft? I've had enough lifted vehicles and to me it feels like the front driveshaft is out of balance. Anyone else?

My third complaint (and this might have been me) is you can't leave the cruise control on at 80mph. It will go into passing gear in a heartbeat. I know the 4L60e transmission shifts by mph so this might be my fault. Before I left town, I used the Superchips programmer to move the shift points. I extended them by a couple of clicks so it would stay in gear longer before it shifted. Would that have affected how easily the trans would go into passing gear. It's like the kickdown setting was low. It wouldn't just drop one gear, it was going down two gears when the cruise was on.

Of course, the truck is so gutless, going up any kind of incline, it would at least drop one gear if I wasn't using the cruise.

I'm going to look into a supercharger. I can't drive a vehicle on the highway that can hardly maintain an 80 mph speed...

Any help or suggestions would be appreciated.

Mark

[OrangeCrush]

Okay, got back to NC from Fla. late last night. This is my first trip with the lift kit. I wasn't sure after installing the 4.56 gears if they would make up for the 38" taller tires.

First, I am truly disappointed in the performance. I installed the Volant air intake, 4.56 gears, Magnaflow exhaust and the SuperChip's programmer. I wasn't expecting seat of your pants performance difference but was hoping for something...anything.

The entire 1200 mile trip, I averaged 10.0 mpg. I was running 80-85 down there for the most part and stayed under 80 mph all the way back.
I realize that the gas mileage drops at speeds over 55 but I thought I'd at least average 12'ish mpg.

Secondly, I didn't notice on the way down but on the way up, I COULDN'T drive over 80mph. I'd get a terrible vibration. I don't think it was anything to do with tire balancing as a)usually you can feel it in the steering wheel fairly easily. and b)if you do have a tire out of balance, it's not normally in the 80mph range and if you increase the speed by 5-10mph, the wobble goes away.

My vibration felt in the drivetrain and stayed with me until I hit 95mph. I don't know if it would have gone away at a higher speed but bad tire balancing usually goes away 5-10mph faster.

Has anyone using the Fabtech kit had a vibration problem from their front driveshaft? I've had enough lifted vehicles and to me it feels like the front driveshaft is out of balance. Anyone else?

My third complaint (and this might have been me) is you can't leave the cruise control on at 80mph. It will go into passing gear in a heartbeat. I know the 4L60e transmission shifts by mph so this might be my fault. Before I left town, I used the Superchips programmer to move the shift points. I extended them by a couple of clicks so it would stay in gear longer before it shifted. Would that have affected how easily the trans would go into passing gear. It's like the kickdown setting was low. It wouldn't just drop one gear, it was going down two gears when the cruise was on.

Of course, the truck is so gutless, going up any kind of incline, it would at least drop one gear if I wasn't using the cruise.

I'm going to look into a supercharger. I can't drive a vehicle on the highway that can hardly maintain an 80 mph speed...

Any help or suggestions would be appreciated.

Mark

[shipbldr]

Wow! Great detail... you've given me a lot to think about!

I can tell you that the SC will completely change the highway manners...

Please keep us posted... you've really got me thinking.

[HGW]

Some people on here are sold on Fabtech. For me, the jury is still out. I do not like the fact that the front wheels are 2" wider than the rear with the Fabtech--due to their spindles. I also have fixed some because the panhard bar bracketry is sub par.

At higher speeds, the kit just does not perform in my opinion for a number of reasons. In your post, it does sound like a driveshaft balance issue but there are many other things that could cause it. To save yourself some bucks, just remove the front driveshaft and take it out for a spin.


If you are close to NJ, I will fix the kit's weaknesses for you!

[Fastest H-Town Realtor]

Ahh,the wonders of modifications..Sorry to hear you have probs, but hopefully they are an e-z fix

1-The idea that any manufacturer would leave an appreciatable amount of coveted HP on the table with something as easy as exhaust of intake mods is the folklore of vaporware. The mods listed, less the gears, do little to improve HP. Maybe, maybe you gained 10 hp. The gears simply made up for the tire circumference increase. And, at that, prolly stole the hp you gained in parts. Bigger gears=More HP to drive them. For the missing MPG's, see previous line.

2-Vibration= rims/tires/recip items-Rotate the wheels front to back. Did the vibration change? No? Go to the drive shaft(s). FWIW, did you see the balance on the tires? Does the wheel/tire combo have a ton o'weights on them? These areas are both problematic. An installers idea of "close enough" may not be. And any tire with a truck of balance weights on it needs to be broken down and rotated 180 degrees. Or replaced.

3-Adding those gears plays havok with the trans settings. Yea, the tires to sort of offset that, but,HummersGoneWild correct me if I am off, but the trans also uses a vacuum modulator. The added strain of the tire/gear combo makes the trans think it is doing more work than what it really is. Hence, the itchy trigger finger.

Anytime you have driveability problems, another mod is the last thing you want to do. Fix the current combo-then add more power.

And remember-bigger tires/wheels/gears soak up HP/torque big time. Something has to turn them.

[JamesT]

OK I had to see if mine did any of this. Remember what mods I have...see below.

I dont think I've ever hav mine past 70 so it went out on the freewat and tested it.

Got it up to 90 and stayed at 90 for approx 15 miles. I noticed no difference in the ride. 19 or 90 it was VERY smooth. I think its the tires you run. I tried 3 brands before my ride became what it is now. Each tire took less than 8 oz. to balance out.

IMO...

James

[MSeeb]

Before I installed my SC on my 03, I had the same issues of the transmission kicking down a gear, sometimes even two gears on mild grades. Once the SC was installed, this no longer happened. A supercharger should help.

[VTSTOMPER]

funny how when you start big mods...it leads to other big mods!

[OrangeCrush]

Guys,

Thanks for the suggestions. After modding about every vehicle I've ever owned, I know all too well the effects of adding another mod without fixing the current problem. And as anal as I am, there is no way I won't make it perfect first.

I took the truck to my shop and put it on the lift. On the bright side, I found why I have a vibration problem. I can grab the rear of the front driveshaft and wiggle it back and forth at least 1/8". The bushings/bearings in the front of the transfer case is worn out. I'm not sure that came from an out of balance driveshaft or the fact that the truck has 53K miles on it and with the new driveshaft, it became more apparent.

I guess you're right Phil, 10mpg isn't bad considering my average speed was 69 mph over 1200 miles. That's a pretty high average speed. Other than when we got stuck in traffic, we were running 80'ish the whole time. I guess averaging 10 isn't bad.

Besides, I didn't buy the H2 for gas mileage.

Hey Phil, you said you LOWERED the shift points?? I did the opposite. I raised them to drag out whatever particular gear I was in and therefore raising rpms before it shifted.

Should I have lowered it and made it shift sooner?

Thanks everyone for the help.

Mark

[HUMMERcustoms.com/TAZ]

I think the H2 does not have vacuum modulation. It is electronically controlled. That is the reason I will be going to vacuum modulation to still get the benefit of higher line pressure but, smoother shift.

The vacuum makes the shift a little smoother rather than a bang when it shifts like it does if You have tuning running at firm shift.

If You play with line pressure try to keep it at low 200 PSI. Stock runs 175 PSI. You can do seriuos damage if You get line pressure to high say 250 PSI & up. You will loose the benefit of removing torque to make tranny last longer.
You will burn bands up by making them hold longer than what You really need. Same problem if you run HP on the 175 the tranny is going to slowly slip into next gear because of to low line pressure and it just slips and burns the bands. So You have to be careful on both ends of the scale and use a happy medium and the research i have done says stay in the low 200's PSI. This way You get the best of both.

It is not just throw all the line pressure You can as it will die on You at some point and You would most likely have gotten longer usage havng it in the stock pressure.

TAZ

[JamesT]

Phil,

I wonder why I get 12 and you get 10. We have almost identical set ups??

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PhilD:
I get 10 mpg on a good day, as low as 8.5 mpg on a bad one. If a lifted H2 does much better than that, then you are doing well in my view.

Never had vibration from the front driveshaft, nor the rear for that matter. Driveshaft issues are often like tire balancing issues and often will only resonate at certain speeds, although I wouldn't expect it to be from 80-95 mph. I'd make sure all the bolts are tight too, as they can vibrate lose.

I use a Superchips and lowered the shift points and it drives fine for me. The cruise control would always kick down even when my truck was bone stock and I rarely use it anymore. With the SC programming, it still kicks down on hills, but isn't too bad, but still annoying enough not to use. </div></BLOCKQUOTE>

[OrangeCrush]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PhilD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by OrangeCrush:
Hey Phil, you said you LOWERED the shift points?? I did the opposite. I raised them to drag out whatever particular gear I was in and therefore raising rpms before it shifted.
</div></BLOCKQUOTE>I lowered them so it stays in gear longer as speed decreases, this seems to work for me and gets rid of some hunting issues I had around 60 mph, when it would all too often jump between 3 - 4 and 4 - 3.

I also raised the shift pressure, not so high to feel a "bump" though.

Here's the setting's I use for my truck with 38's

Gear Ratio: Stock
Tire Height: 36.75"
Shift Point 1-2: Min - X - - SC - - - - Max
Shift Point 2-3: Min - X - - SC - - - - Max
Shift Point 3-4: Min - - X - SC - - - - Max
Shift Pressure 1-2: Min - - - - SC - - X - Max
Shift Pressure 2-3: Min - - - - SC - - X - Max
Shift Pressure 3-4: Min - - - - SC - X - - Max </div></BLOCKQUOTE>

Phil,

Thanks... my brain doesn't comprehend it, seems opposite to what you'd want but I'm gonna change it out and try that setup. One question though... did you use the performance setup or the 87 octane setup?

Thanks,

Mark

[OrangeCrush]

Just got back from a test run. Completely drove like a new truck. The shifting was faster and firmer. Put the engine in the cam's powerband and makes the truck much more responsive.

If I could only make the top end like the bottom end, I wouldn't need a supercharger...

Thanks for your help Phil.

Mark