4 gsk with a auto trans???

hereismylife

hereismylife

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Jan 5, 2009
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I put my springs in a while back. I watched what they will do and such now I am just wondering this.

I can rev to 4000 and that is fine. If you are driving it will pull hard to 2500 then it seems like like you over rev it past 2500 and you need to shift.

My question is what do I need to do so it will pull hard to 3500 to 4000 rpm?

thanks

Read more: 4 gsk with a auto trans??? - Diesel Bombers
 
My 96 does the same thing. I installed the 4k kit per smokems instruction, leaving a few springs out. It free revs to about 3200 which is about what he said it would do. When driving, if I get past 24-2500 it loses a lot of power. I think my timing has slipped some and my stock turbo limits me on the top end??
 
I wish I could get some video of someone driving reving it out to 3500 to 4000 with a auto. Maybe it is just the turbo is out of air. I would like to know what the problem it. It would be great to pull to atleast 3500 then stop....hhhhmmm
 
It takes alot of fuel/air to make power beyond 2500 with these engines. Even heavily modded trucks seem to fall off at about 3200-3500 rpm. Timing does affect your rpm range, but without supporting mods It doesn't help to add a bunch of timing.

Derek
 
so what you are saying I need more boost lets say 60 instead of 30? Also a bigger turbo?
 
More boost out of the hx35 won't make more power, just heat and back-pressure. Not to familiar with autos, but my 5 speed seems to pull pretty good, although the turbo is pretty much at a loss past 2800. I'm just chucking black smoke w/40psi over 3k or so. Maybe you auto guys are jsut blowing through the converter?
 
I would maybe agree but I have a 3 disk billet converter. I lock it at 40 and it pulls just to 2500-2600 then takes forever to 150 mph

If I could find a different turbo to try for a day then I could find out what is going on....
 
j_k_auto said:
so what you are saying I need more boost lets say 60 instead of 30? Also a bigger turbo?
Click to expand...

More boost won't help. You need added airflow. When you add a bigger turbo then you will need to add fuel. A cummins is no different then any other engine, everything has to work together.

Derek
 
Oh here we go again with the turbo thing.... I was thinking about putting a 14 or 16 cm exhaust housing on and seeing if that would help. I think that is what is hurting us 12v owners......
 
I went to a 14 housing on mine and noticed very little change. I would just upgrade to a s300 based turbo, then you'll notice the extra airflow.
 
My truck pulls hard right to 3500-3600 rpm and when it shifts it never drops below 3000. But I have a 66mm turbo on mine.
 
j_k_auto said:
Oh here we go again with the turbo thing.... I was thinking about putting a 14 or 16 cm exhaust housing on and seeing if that would help. I think that is what is hurting us 12v owners......
Click to expand...

I swapped the 18.5 exhaust housing on from my 1st gen and the added airflow didn't help any. The problem is that the compressor isn't moving enough air at that RPM to make power, so no matter how clear the exhaust path is, not enough fresh air is being introduced by the HX cold side to burn the available fuel, so the engine falls on its face. I swapped back to the 12 within a week. much more fun to drive, still no power up top, but that's why guys step up to bigger overall turbos, IMO. Wish I couldLOL
 
If you want to make power you had better be looking at bigger turbos. An hx35 with any exhaust housing on it isn't going to help. Your problem is a lack of airflow on the cold side.
 
mondtster said:
If you want to make power you had better be looking at bigger turbos. An hx35 with any exhaust housing on it isn't going to help. Your problem is a lack of airflow on the cold side.
Click to expand...

This would be correct. it doesn't matter how high you can rev or how much fuel you have if you don't have the airflow to support it. a bigger turbo is a must for the added airflow your looking for... hx35s tend to fall on their faces right around 3k depending on your setup
 
The first thing I would do is put a pressure gauge on the fuel system. A temporary gauge on the fuel filter housing with enough line so you can see it when driving. Without enough pressure it will nose over like your talking.
 
You need MORE TIMING!
Put the power up in the higher RPMs.
Heck, pullers run in the 30s and 40s IIRC.
 
I think you've got some issue other than the turbo. When I had a stock turbo and 4k springs bringing it up to 4k under a load then grabbing the next gear was never a problem. I never felt like I was loosing any power or defueling. I even pulled my truck and was able to maintain 3800 rpm down the track. The only mods I had was 4kgs, 60lb springs, boost elbow, and a 100 plate full forward.
 
Thanks for the input guys. I know I am getting plenty of fuel from what I have tested.

I will have to look at turbos or at least housing upgrades.

Something like a 64/14 or64/16 or 62/?

Yea it pulls like a rape date of the line at the track but lacks at the top end pretty bad. smoke the how way down till I let off......:rockwoot:
 
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