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Discussion Starter #1
I have been thinking of swapping out my current turbo...

After having so manny issues with a 4L80 and converters, I finally swapped to a Th400. Now it is harder to spool turbo. First conveter came in way to tight and sent it back for restall... Neal chance told me they wouldn't go more than 500 rpm more, because it would lead to probably start having issues blowing through it again.
Put new converter in and it is better but still not happy. Initial foot stall is 3100-3200 rpm, then can sit on it, and will get to 3500 then as boost starts coming in will go higher.. I stop it at 4000 on 2 step and get 5-6 psi. But the whole process takes way to long and causing plenty of heat

Rather than changing conveter out, I have thought of changing turbo or going to twins. The current turbo I have on it was purchased with the intent of going 427ci, but will not happen yet.

On 18-19 psi, 10psi launch, 1.48 60 ft, in San Antonio
Truck went [email protected] mph on the 4L80
Bouncing off rev limiter on the 1-2 shift. Could never make it shift right under full power. Low power was no issue
And a couple of 10.00 passes then tranny let go again.

Have only taken to track once on the TH400
On 18-19 psi, 5-6 psi launch, 1.61 60ft, in Amarillo 6600 DA
Truck went [email protected]
Broke tires loose every time top of first going into second.
Suspension would not stay planted where boost was slow to come in.


Current setup:

99 GMC RCSB
Garret 98MM - Large frame
3" id custom KB Log
9.5:1 408
235 trick flow heads
235/235 .610/.610 114+4 cam
Vic jr intake
90mm TB
120# injectors
Dual A1000 pumps
A/W Intercooler
Alky Control dual nozzle
Running pump gas
Neal Chance conveter
TH400
3:42 gear
29.5x10.5 rear tire



Looking for ideas... Thx
 

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Discussion Starter #2
Have been told by a few that this turbo is fine, other say that can't believe it's not choking with 1.0 a/r

Might just loosen converter more.

Have seen another truck very similar build with a PT88/91, spooled very quick and truck went 8.80's...
 

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Who your getti g the converter from is an issue

Lenny at Ultimate did a converter for one of my customers cars that will stall 4000 on a footbrake...4700 on the transbrake and has less than 5% slip at 7800.

compressions low.

Cam is leaving something on the table.

Rear gears wrong.

Turbo is effin huge. You could drop down to a GT55 sized unit amd eliminate alot of your spooling issue.
 

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Discussion Starter #5
This has been a learning experience as I go...

Converter will go back one more time. Neal chance told me the issues was that I was only spinning motor to 6500-6600 rpm. Not enough there to couple conveter. Once boost starts coming in I can take it past 4300 very easy

Compression, what would you suggest, that seemed to be the number most builds I saw where going for.

Cam was speced by Par G, but I have no problem re-specing and changing it out.
Current Springs are good for .700 lift.

Gear ratio, seems to be working for others with trucks, or 3:50 ratio... What size did you have in mind?

I had looked into a GT5518, but didn't want to just throw money at it without others looking at the whole picture and sharing some of there experience.

Thx for the pointers, I will be giving both of you a call..
 

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Is this a 2 or 4wd truck?
 

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I have been thinking of swapping out my current turbo...

After having so manny issues with a 4L80 and converters, I finally swapped to a Th400. Now it is harder to spool turbo. First conveter came in way to tight and sent it back for restall... Neal chance told me they wouldn't go more than 500 rpm more, because it would lead to probably start having issues blowing through it again.
Put new converter in and it is better but still not happy. Initial foot stall is 3100-3200 rpm, then can sit on it, and will get to 3500 then as boost starts coming in will go higher.. I stop it at 4000 on 2 step and get 5-6 psi. But the whole process takes way to long and causing plenty of heat

Rather than changing conveter out, I have thought of changing turbo or going to twins. The current turbo I have on it was purchased with the intent of going 427ci, but will not happen yet.

On 18-19 psi, 10psi launch, 1.48 60 ft, in San Antonio
Truck went [email protected] mph on the 4L80
Bouncing off rev limiter on the 1-2 shift. Could never make it shift right under full power. Low power was no issue
And a couple of 10.00 passes then tranny let go again.

Have only taken to track once on the TH400
On 18-19 psi, 5-6 psi launch, 1.61 60ft, in Amarillo 6600 DA
Truck went [email protected]
Broke tires loose every time top of first going into second.
Suspension would not stay planted where boost was slow to come in.


Current setup:

99 GMC RCSB
Garret 98MM - Large frame
3" id custom KB Log
9.5:1 408
235 trick flow heads
235/235 .610/.610 114+4 cam
Vic jr intake
90mm TB
120# injectors
Dual A1000 pumps
A/W Intercooler
Alky Control dual nozzle
Running pump gas
Neal Chance conveter
TH400
3:42 gear
29.5x10.5 rear tire



Looking for ideas... Thx

Take the cover off and measure the wheel. Easy to identify. GT55 would indeed change the response quite a bit.
 

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Discussion Starter #11
Can you give me the specs on the GT55?
And do you take trade-ins?? Lol

Goals for truck are mid to low 9's...
Not sure what stock block will handle, or what people are pushing them to nowadays.
Truck weighs 4450 with me in it, hope to put it on a diet soon

PM me a price
 

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Can you give me the specs on the GT55?
And do you take trade-ins?? Lol

Goals for truck are mid to low 9's...
Not sure what stock block will handle, or what people are pushing them to nowadays.
Truck weighs 4450 with me in it, hope to put it on a diet soon

PM me a price
pm sent
 

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The weight, rear gear, tire size and low shift rpm does make it hard on the converter to couple and still be easy to spool. If the turbo is a large frame its on the large side for sure. I'd put a turbo on it that better suits your needs but I can also spec a PTC converter that will spool faster without giving up slip. Looser down low, tighter up top.
 

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From my experience sizing the turbo for your goals will make things a lot easier on you. I don't think Neal Chance did anything wrong, part of your combo is a 1600 horsepower turbo, you are using about 950 of that. Sizing the turbo will make the power earlier and probably make the truck quicker.

We have had really good luck with the Borg Warner stuff. For the price it is hard to beat.

From what I have seen out of a BW cast s480 out here in West Texas it would put your truck in the 9.35 range.

With a billet wheel you can get a little more power potential without any downside other than a little extra price.
 

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Discussion Starter #15
From my experience sizing the turbo for your goals will make things a lot easier on you. I don't think Neal Chance did anything wrong, part of your combo is a 1600 horsepower turbo, you are using about 950 of that. Sizing the turbo will make the power earlier and probably make the truck quicker.

We have had really good luck with the Borg Warner stuff. For the price it is hard to beat.

From what I have seen out of a BW cast s480 out here in West Texas it would put your truck in the 9.35 range.

With a billet wheel you can get a little more power potential without any downside other than a little extra price.
I know what you mean, I took this turbo in on a trade with the
intent of building a 427 LSX down the road.
Calculated 4450lbs and 143 trap speed about 1050 rwhp, no where close to 1600hp..

Was not trying to say Neal Chance was the problem, was just stating what they told me they could do for me.

I am looking into a 83MM from Steve Morris or a S588 made by them
 

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Ah ok ;)
I would go with the new BW billet 84/100, or Gt5088 on that with a yank sc3000 or py3400 or ptc converter. Also need to ditch the pump gas if you plan on pushing it to 20+ psi. I have a cam that works well in the 88-94mm 408 trucks that isn't too far from where you are now but might help a little. The tighter the converter you can get away with the better the truck is going to run IMO.
 

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Discussion Starter #17
Who is making the 84/100?
Same thought about converter, but need to be able to spool, lol
I like the rpm drop and power now, just takes way to long to come in.
I should have a turbo ordered next week, just to many decisions and choices..
 

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Jose at Forcedinductions builds it. A 408 should have no problem spooling a 84-88mm with a Py3400. My 6.0 spooled a PT88 with no problem at all, it even spooled in 8000+ Da.
 

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Discussion Starter #19
I do add race fuel to it at 18+ psi

The converter I have now is about 3400-3500 foot brake
 

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Discussion Starter #20
Yeah the 88mm shouldn't be a problem..
I recently tuned a 4.8 with a PT88 and was surprised at how well it spooled.

Just don't know and learning about what would work on turbine side to not choke the 408
 
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