diesel swap?

[ccmf22]

okay i was wondering what it would take to swap in a 6.5td into my chevy k20 my drive train is 350-th400-208, from what ive gathered it theoretically is a direct swap in, the only issue is the transmission is a vacuum operated so in theory i would just need an automatic shifter like a b&m, any thoughts??

 

[adamv7010]

Many 6.2 came w the 400 or 700r4...the 6.2 ans 6.5 are very similar.

 

[ccmf22]

i was thinking about the 6.2 aswell but the vacuum modulator is still an issue im trying to look up ways around it still

 

[HotRodPC]

It can easily be done Chris. The CUCV military trucks are 6.2/Th400/NP208, so figure out what they are using for vacuuum modulation and problem solved. Its an OEM fix obviously. I happen to have an 85 K10 that was originally 6.2/700r4/NP208. Its not going back to 6.2. The engine harness has been butchered by the idiots I bought the truck from, so no help there for you, but I might have some other diesel related cab parts. Not 100% sure yet if I am going to use it, but for example I still have the Diesel Instrument Cluster with the D321 shift indicator. And likely the wiring harness to the cluster too. You won't have to use a B&M Shifter, you can use the same shifter tha is in the truck now.

 

[adamv7010]

Don't the 400 use an electronic kickdown rather than vaccum ?

 

[HotRodPC]

Don't the 400 use an electronic kickdown rather than vaccum ?

Nope. The Th400 shift points are determined by the Vac modulator, and governor only. NO CABLE AT ALL. Then you have an electic solenoid for full throttle downshift only and does not determine shift ponts at all.
You might be confusing the 4L80-E which is the Th400 overdrive model. Same gear ratios, many interchangeable parts etc. But the 4L80-E must have an ECM to control it since it does NOT have any governor, modulator on kickdown solenoid. Its all computer controlled, unless you go with a modified full manual valve body which take all auto aspects out of it. You must shift it manually.

 

[ccmf22]

hey guys sorry its been awhile ive been dumping all my money into my truck to fix her haha its been an interesting few months flywheel, new carb, wrecked 14 bolt etc etc, but yeah im still looking up how on the cucv they swapped or changed the vacume modulator

 

[HotRodPC]

hey guys sorry its been awhile ive been dumping all my money into my truck to fix her haha its been an interesting few months flywheel, new carb, wrecked 14 bolt etc etc, but yeah im still looking up how on the cucv they swapped or changed the vacume modulator

I believe that was converted to a cable operated mechanism that ran off of the throttle linkage. Very similar to what Th350 uses a detent or kickdown cable except it hooks and bolts to the vac modulator valve orfice instead.

Welcome Back !!!

 

[Stroked]

6.2/6.5 both have an aux. vacuum pump on them. On 6.2's it's ran off the cam like a distributor and on 6.5's I believe it's belt driven like other acc.

Here's the 6.2 vacuum pump:

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And here is the 6.5 vacuum pump. It bolts to the acc bracket I assume and is belt driven:

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[Jims86]

I believe that was converted to a cable operated mechanism that ran off of the throttle linkage. Very similar to what Th350 uses a detent or kickdown cable except it hooks and bolts to the vac modulator valve orfice instead.

Welcome Back !!!

The th 400 had an electric kickdown, that was operated by a switch on the gas pedal bracket.

 

[HotRodPC]

The th 400 had an electric kickdown, that was operated by a switch on the gas pedal bracket.

I'm fully aware of that if you can believe that.
But we're reffering to what was hooked in place of the vacuum modulator to determine shift points in diesel trucks.

 

[Jims86]

I'm fully aware of that if you can believe that.
But we're reffering to what was hooked in place of the vacuum modulator to determine shift points in diesel trucks.

Hmmm...
that would be an interesting setup.

 

[Stroked]

There's a vacuum regulator valve on the side of the injection pump that changes the vacuum signal based on how much throttle you're giving it. Vacuum line runs from the vacuum pump, to the IP, and then to the transmission.

That's how my parts truck was. Unless I'm reading your question wrong

 

[HotRodPC]

There's a vacuum regulator valve on the side of the injection pump that changes the vacuum signal based on how much throttle you're giving it. Vacuum line runs from the vacuum pump, to the IP, and then to the transmission.

That's how my parts truck was. Unless I'm reading your question wrong

That is very possible. I'm not saying it's done by cable. I'm saying, I have seen it done that way, and know the product exists for things like Cummins Conversions or If you have ECM Controlled motor and would like the ECM to have partial control of the Non Electrnoic Auto Trans.

 

[Jims86]

That is very possible. I'm not saying it's done by cable. I'm saying, I have seen it done that way, and know the product exists for things like Cummins Conversions or If you have ECM Controlled motor and would like the ECM to have partial control of the Non Electrnoic Auto Trans.

The modulator would have to have a reversed action from the one on the gasoline powered models, where vacuum decreases with throttle input, and if the diesel version uses vac from an engine driven pump, it would have to wait for the engine to spool up to have any effect when you plant your foot.