Truck wont run in 3rd gear??

[Baged72]

Finally got my truck going so its drivable and it will lite up the tires 1st through 2nd and as soon as the truck hits 3rd gear it bogs down and will even shut off if I reach higher mph, any ideas???

400 smallblock
TH 350

[sean1969c10]

Could be running out of fuel, 1st thru 2nd running on what is in the float bowl and what the fuel pump can add but the pump ends up running behind and by the time you hit 3rd gear you don't have enough fuel in the bowl. Just my 2c worth

Sean

[crushermechanic]

x2 sounds like maybe the float level is to low. it could also be the pump is weak.

[longhorn396]

my trans pump just went out of mine and it was doin close to the same thing. so it might be the pump

[Baged72]

I can drive my truck all day long in 1st and 2nd gear but once i hit 3rd it happens......
I have a brand new holley 600 carb and a new electric fuel pump, what is a transmission pump??

[longhorn396]

well the guy working on mine said that there is a pump right behind the first panel behind the bell housing on the inside. idk i have never worked on a trans but just my 2cents. idk

[69GMCLonghorn]

I don't think this is trans related at all... This sounds like a classic case of fuel loss, as prev stated. Even a new carb can either have a problem, or just can't keep up if your foot is in the secondaries... I've had this happen on a Chevelle that I had. It would bog down if I had the secondaries open for more than a few seconds. I'd take my foot out of it and it would recover, then I could nail it again... No wonder I wore that engine out!! I think the secondaries were open more than they were closed!

[longhorn396]

i thought u meant it was slipping. my bad man. sorry bout the wrong info

[Baged72]

It feels like its running out of fuel but... in 1st and 2nd dont the secondaries open up also? I have it to the floor throughout 1st gear and also 2nd, doesn't the carburetor act the same as it would in 3rd? Do i need a regulator that produces more psi? I have a basic 1 to 6 psi regulator and its on 5psi now.

[longhorn396]

Its probably like everyone else is sayin. it probably just sucking all the gas and not getting enough to get it back in time. and yes they do open also. Not sure bout the regulator psi. Do someresearch and u might be able to find it.