Chev truck transmission

RVS · Jun 17, 2015

Looking at putting a 6.5L diesel into my 1979 Chevy 4x4. It has a turbo 350 automatic transmission in it. Will it bolt up to the 6.5L. Has anyone done something like this before any advice will help.

Bob · Jun 17, 2015

Tranny will bolt up. Only issue MAY be the torque converter bolts... NOT sure if there's a dual bolt pattern flex plate available, or if three holes would have to be drilled.

You will need to get injection pump set up with vacuum valve to operate modulator or get a mechanical cable modulator conversion.

They used the THM400 with the 6.2, I would think the IP vacuum valve for that setup would work.

RVS · Jun 17, 2015

Thanks that's what I thought but I haven't done to much with the newer 6.5. The 6.5 has a vacuum pump on it already.. Will that work or do I still need something else.

mite-help · Jun 17, 2015

thinking about doing this, only in reverse. have a 93 with sick 6.5. have 350 tbi gas engine in shop. I like this old 6.5 diesel, but from what I,m seeing [lost piston, I think] may be out of range to repair.

Bob · Jun 17, 2015

The vacuum pump is the SOURCE of the vacuum, you also need an attachment to the throttle shaft on the IP that REGULATES the vacuum sent to the transmission based on throttle position.

Glenn/Mn · Jun 17, 2015

i run a 6.5 with a 400 tranny I have removed the vaccum pump as it only controlled the waste gate vacuum and I installed a shorter belt and a spring controlled boost on the turbo that you can adjust, been running this way for years no issues, I have replaced heads 4 injection pumps and rod and main bearings I am not aware of any other device controlled by vaccum the 400 is electronically controlled, the 350 I not aware if a vacuum is needed, the 6.5 vaccum pump is a POS, removing it will gain a little more MPG

Bob · Jun 17, 2015

HMMMM, I was not aware of an "electronic" THM400.

The updated successor to the THM400, the 4-speed 4L80-E which uses some THM400 parts was, of course, electronic. Is that what you have or is there a late version of the THM400 that's electronic that I am unaware of?

<img src = "http://i160.photobucket.com/albums/t188/TimAT_vette/TH400/DSC00212.jpg">
Note the vacuum modulator extending downward at the lower left of the THM400 in the photo.

bondodust · Jun 17, 2015

When you are switching trans you will have to have a torque convertor for a diesel. Gas engines can use the diesel convertor, but diesel can't use a gas convertor because of wrong ratio and stall speed. Found this out in my younger days of doing transplants for people.

Glenn/Mn · Jun 17, 2015

it must be the 4L80e as I crawled under and saw no vaccum lines unaccounted for, when I blew the tranny cooler in the radiator I got water into the tranny, it wasn't much but I had it rebuilt and updates were installed, I think there was a learn period before the program was burned in or so I was told by the rebuilder, I have hauled a bunch with the tranny and it never failed, the rebuild was because I could not control the temps and I ran in the 260's sometimes, this led to an early failure of the tranny oil cooler, it was then I started down the path of the updates

used red MN · Jun 17, 2015

Beware if you plan on using the stock gasser torque converter. Diesel models were heavy duty with extra internal welding to with stand the greater torsional vibration. Your milage may vary.

jimg.allentown · Jun 17, 2015

What you really need is a donor vehicle so you can get ALL of the parts you need. It is simply not as simple as bolting up to a transmission.
In answer to your question, I do not know if it will bolt up, BUT I do know that if it does, it may not work for long. The 350 transmission was a good reliable transmission in its day. BUT, it is NOT up to the torque output of a diesel. Also, it is only a 3 speed trans. No overdrive. The diesel takes a low stall converter while the gas engine takes a high stall converter. What that translates out to is that when your diesel is just about all wound out, the converter will just be starting to "hook up." Typically, gas engine converters have a 2500 to 3000 rpm stall while a diesel makes its peak torque and power at about 1200 to 1500 rpm.
You will also need the fuel system, motor mounts, exhaust, wiring harness, and front suspension parts for the diesel.
There has not been enough money printed to this date to get me to ever do another conversion. The headaches involved are enough to make Mother Therese curse and P. O. the good humor man.

Mike M · Jun 18, 2015

I did the opposite. I put a 1969 327 in my 1982 (or 83 ?) K10 with auto. Got rid of that JUNK 6.2L diesel.
IIRC I used the torque converter and motor mounts right off the diesel. It dropped right in. Only fab needed was to rework the power steering pump bracket and rig up coolant hoses.
Put a gas engine in your truck you will be much happier in the long run. If you want a diesel then stick a cummins in it !

RVS · Jun 18, 2015

I have a complete donor truck engine tranny and all the bits and pieces. Was going to put the whole unit in the 79 but the driveshaft for the front diff is on the wrong side. that is why I was going to use the original tranny. Will have to look into the torque converter and see if this worth the work. Just have some time off from work this summer and if I'm working on a truck in the shop it keeps me out of my wife's line of sight. This will be a toy project not an everyday driver or work truck.Thanks for the info from everyone. Will let you know if and when I get started and how it works out.

TGP · Jun 18, 2015

Also need to change the Transmission Shift Governor.
Different between gas and Diesel
TomP

RVS · Jun 18, 2015

Ok it sounds like a lot of figuring out for the torque convertor and vacuum issues. Can I exchange a transfer case from a 350 to 4L80E tranny to get the driveshaft on the proper side for my 79

buickanddeere · Jun 18, 2015

10 times more bother and 10 times the expense than what it's worth.
What are your goals with this project ?

RVS · Jun 18, 2015

As I mentioned below it is a Toy project not a daily driver or work truck. I have those already. I am off for 2 months this summer so I need something to work at to keep out of my wife's radar. As mentioned already I have a complete donor truck to use as a parts depot. So cost should not be to big of an issue and besides it's my money!! But thanks for your concern.

buickanddeere · Jun 18, 2015

(quoted from post at 16:26:09 06/18/15) As I mentioned below it is a Toy project not a daily driver or work truck. I have those already. I am off for 2 months this summer so I need something to work at to keep out of my wife's radar. As mentioned already I have a complete donor truck to use as a parts depot. So cost should not be to big of an issue and besides it's my money!! But thanks for your concern.

As previously stated. Without overdrive it`s going to be a dog in 1st gear and barely make freeway speed in high gear.
There are full manual valve bodies to bolt onto TH700R4 and 4L60E transmissions. Operate the torque convertor lockup via a throttle position switch.

Dave in GA · Jun 18, 2015

If you really want to have some fun, why not put a John Deere diesel in it, and a manual tranny? Or pick up some other engine from a tractor junkyard. Maybe you could find a nice Perkins. A few years ago, there was a guy on here who was fitting a Deere engine into a Chevy pickup, I think it was.

bison · Jun 18, 2015

(quoted from post at 08:52:39 06/18/15) I have a complete donor truck engine tranny and all the bits and pieces. Was going to put the whole unit in the 79 but the driveshaft for the front diff is on the wrong side. that is why I was going to use the original tranny. Will have to look into the torque converter and see if this worth the work. Just have some time off from work this summer and if I'm working on a truck in the shop it keeps me out of my wife's line of sight. This will be a toy project not an everyday driver or work truck.Thanks for the info from everyone. Will let you know if and when I get started and how it works out.

You will need to swap entire wire harness from the dash and the ECM from the diesel in as well.+ the rad and oil cooler and numerous other things.
And The brake booster as well

You will curse the day you started on it.

RVS · Jun 19, 2015

Hi Bob Since it looks like you have seen a transmission, can I exchange the transfer case from my 350 to my 4L803 transmission. I need to come out of the other side to match up with my front diff on my 79.

Chev truck transmission

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