turbo 350 behind cummins, PLEASE HELP!!
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From: live oak, ca
turbo 350 behind cummins, PLEASE HELP!!
we are doing a conversion on a 75 chevy, got it all hooked up and maybe driveable tomarrow, but how does the kickdown and vacuum systems work on the turbo 350? my understanding is that the kickdown is only used for full throttle downshifts, is this correct? and the vacuum... does it need straight vacuum to shift, or or will it shift way to soon with vacuum all the time? i can make a bracket and extention to get the kickdown to work, but what do i need to do with the vacuum, anyone done one of these yet?
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ok, i think i got it after about 4 hours of searching... looks like the kickdown does only control the full throttle downshift, there is a vacuum regulator valve on early 80's chevy 6.2 diesels, (AC Delco part number 14057219) that controls vacuum to the trans via throttle position (mechanical linkage) to control part throttle shifts, and there is a trans govenor calibration kit offered by B&M to adjust wideopen upshifts... UGG looks like just more work and $$$, but oh well, the best part is all this stuff will also work for the turbo 400, the 350 we have is very strong, so we are gona run it till it dies, we have a good 400 sitting on the shop floor to start building on soon...
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okay.... wrong again, the chevy vacuum regulator would work but would be a real PITA to hook up, however i did find a conversion kit on ebay to turn the vacuum modulator to cable operated for $120 and still need a cable, so once again just more $$$$$
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If i am not mistaken, the 6.2's used a TH400, which was electronic kickdown with a switch on the gas pedal.
The cable on a TH350 as you said, is for "passing gear" (just kicks it down to the previous gear in proportion to vehicle speed).
The vac modulator controls "when" it will shift in proportion to engine vacuum.
They make adjustable modulators which will raise up shift points by limiting vacuum, and they also make governor kits, but either way, you'll need vacuum or it wont shift at all in most cases.
My best suggestion is to just tap it right into the T fitting by the brake booster, which will give it a steady vac pull, and use the adjustable modulator to fine tune it.
I'm not really sure how a TH350 is going to hold up to 600ft/lbs of torque when it shifts, so be prepared to pick up parts with a shovel after the first test drive lol
The cable on a TH350 as you said, is for "passing gear" (just kicks it down to the previous gear in proportion to vehicle speed).
The vac modulator controls "when" it will shift in proportion to engine vacuum.
They make adjustable modulators which will raise up shift points by limiting vacuum, and they also make governor kits, but either way, you'll need vacuum or it wont shift at all in most cases.
My best suggestion is to just tap it right into the T fitting by the brake booster, which will give it a steady vac pull, and use the adjustable modulator to fine tune it.
I'm not really sure how a TH350 is going to hold up to 600ft/lbs of torque when it shifts, so be prepared to pick up parts with a shovel after the first test drive lol
Thread Starter
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Joined: Feb 2008
Posts: 391
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From: live oak, ca
If i am not mistaken, the 6.2's used a TH400, which was electronic kickdown with a switch on the gas pedal.
The cable on a TH350 as you said, is for "passing gear" (just kicks it down to the previous gear in proportion to vehicle speed).
The vac modulator controls "when" it will shift in proportion to engine vacuum.
They make adjustable modulators which will raise up shift points by limiting vacuum, and they also make governor kits, but either way, you'll need vacuum or it wont shift at all in most cases.
My best suggestion is to just tap it right into the T fitting by the brake booster, which will give it a steady vac pull, and use the adjustable modulator to fine tune it.
I'm not really sure how a TH350 is going to hold up to 600ft/lbs of torque when it shifts, so be prepared to pick up parts with a shovel after the first test drive lol
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The cable on a TH350 as you said, is for "passing gear" (just kicks it down to the previous gear in proportion to vehicle speed).
The vac modulator controls "when" it will shift in proportion to engine vacuum.
They make adjustable modulators which will raise up shift points by limiting vacuum, and they also make governor kits, but either way, you'll need vacuum or it wont shift at all in most cases.
My best suggestion is to just tap it right into the T fitting by the brake booster, which will give it a steady vac pull, and use the adjustable modulator to fine tune it.
I'm not really sure how a TH350 is going to hold up to 600ft/lbs of torque when it shifts, so be prepared to pick up parts with a shovel after the first test drive lol
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