TH400 question

[jboyes]

Sorry if this has been asked before, I did a quick search and didn't notice anything that stuck out.

What are the differences between a gas th400 and a diesel th400? Can I take one from a diesel and just bolt it right to my 454 and run it no problem?

Thanks guys,

Jason

 

[76zimmer]

govenor, and torque convertor at a minimum....

 

[imiceman44]

Sorry if this has been asked before, I did a quick search and didn't notice anything that stuck out.

What are the differences between a gas th400 and a diesel th400? Can I take one from a diesel and just bolt it right to my 454 and run it no problem?

Thanks guys,

Jason

the diesel Torque converter and governor shift at lower RPM.
If you use it behind a 454 you might be OK if you don't have an agressive cam.
You need torque at low RPM to run a diesel tranny.
These parts are easy to change before you put it in so find out your engine specs before you put it in.

 

[muddog]

Hey Jason, the vacuum modulater is non adjustable on that one and the converter does have a lower stall versus a gasser. I have run them in my trucks though. THat white tahoe you may have seen yesterday has one in it and i couldnt tell a difference. WElcome to call anytime.

 

[jboyes]

Hey Jason, the vacuum modulater is non adjustable on that one and the converter does have a lower stall versus a gasser. I have run them in my trucks though. THat white tahoe you may have seen yesterday has one in it and i couldnt tell a difference. WElcome to call anytime.

Hey Brian, I meant to ask you yesterday what if it was a diesel or not but forgot. I didn't think it would make that much difference but wanted to make sure I didn't need to change anything before putting it in. I saw the Tahoe, do you guys do a lot of mud bogs? If so, where? One of my buddies built an S-10 just for mud competitions and he was wanting to go to a few if they were fairly close.

I am running a TBI 454 bored 60 over with a mild cam and headers. This is in K5 frame that has no body, it is all tube. It is considerably lighter than a K5. All I do is trails and rocks (mostly at Disney), very little mud.

Brian, if you ever head down to Disney let me know a couple weeks before you do and I could probably get a few guys together to wheel with. March 12-13 is Long John's Big Meat Run. There will be a group of us there for that.

Thanks for your help guys.

Jason

 

[diesel4me]

The diesel torque converter has 6 bolts,and gas ones have 3,but they are the same bolt pattern,so you can bolt a gas version to a diesel,though its probably not recomended,I know a few guys who stuffed a gas TH400 or a 700R4 in place of their diesel ones and ran them ,and they worked fine as far as they were concerned,for street use and light plowing ..(In fact,I'm not so sure my '82 K2500 has a true "diesel" tranny,it has a car type case with a tin flywheel dust cover and no place to bolt up the strut rods to the bell housing!..never looked to see if it had the 6 bolt converter either,maybe it does,maybe not--I have plowed many BAD storms with this truck and had no issues yet,but I barely use it on the road other than dump runs)..

The short answer is yes,you could swap a gas tranny right into a diesel,but how long they live without the proper converter,pressures,shift points from govenor calibration being different,I cant say..I do know some GAS engines used the same 6 bolt diesel torque converter,in fact GM put them in some vehicles that had a recall for vibrations,,and my brother bought a automatic to put in a 78 G10 van he had (was a manual and he wanted an automatic) ,he got it from a 77 GMC school bus van with a 292 and it had the 6 bolt converter in it from the factory..worked fine with his 250 six..

 

[jboyes]

The diesel torque converter has 6 bolts,and gas ones have 3,but they are the same bolt pattern,so you can bolt a gas version to a diesel,though its probably not recomended,I know a few guys who stuffed a gas TH400 or a 700R4 in place of their diesel ones and ran them ,and they worked fine as far as they were concerned,for street use and light plowing ..(In fact,I'm not so sure my '82 K2500 has a true "diesel" tranny,it has a car type case with a tin flywheel dust cover and no place to bolt up the strut rods to the bell housing!..never looked to see if it had the 6 bolt converter either,maybe it does,maybe not--I have plowed many BAD storms with this truck and had no issues yet,but I barely use it on the road other than dump runs)..

The short answer is yes,you could swap a gas tranny right into a diesel,but how long they live without the proper converter,pressures,shift points from govenor calibration being different,I cant say..I do know some GAS engines used the same 6 bolt diesel torque converter,in fact GM put them in some vehicles that had a recall for vibrations,,and my brother bought a automatic to put in a 78 G10 van he had (was a manual and he wanted an automatic) ,he got it from a 77 GMC school bus van with a 292 and it had the 6 bolt converter in it from the factory..worked fine with his 250 six..

Thanks for the info. I am doing the opposite though. Putting diesel tranny to a gas motor. I have also read that you can put a 350 converter on a 400 and it will run just fine. Is this a fact?

I think I will probably just hook it up as it is and see how it does.

Thanks,

Jason

 

[onetonjimmy]

I'm running the diesel th400/convertor with a 454 and d60/14ff w/o any problems. I did install a shift kit along with an adjustable vacuum modulator to firm things up.

 

[diesel4me]

Putting a diesel converter in gas applications just lowers the stall speed some and makes it feel more direct drive,and more likely to want to "creep" at idle at a stop sign--putting a gas torque converter in a diesel raises the stall speed some,and might make it feel like it is slipping a bit (but isnt) ,if your used to the diesel one..

Yes,TH350's and TH400's use the same converters,they are interchangeable.same size and spline ,etc..(excepting the difference in stall speeds and bolt hole count we already discussed)..

Whether or not its true a "diesel" TH400 uses a different case,line pressures,more clutches,etc,or other things are "different" I cant say for sure,but I know many tranny shops here just swap in a diesel govenor and torque converter and slap them in,if its a diesel truck--seeing there aint many diesel "cores" around to rebuild,I suspect they just build a gas tranny to heavier specs and put them in...

 

[muddog]

Brian, if you ever head down to Disney let me know a couple weeks before you do and I could probably get a few guys together to wheel with. March 12-13 is Long John's Big Meat Run. There will be a group of us there for that.

Thanks for your help guys.

Jason

THere are quite a few mud runs around here. THe closest is parker...6 miles from my house. I just take the tahoe on my neighbors and my trails and through his mud pit. Nothing too serious..its too nice..trying to sell it actually so I can build something else. As for Disney, Ill see if any guys from up here are going. Lots of them have their rigs down for the the winter rebuild. They do hit up Disney pretty often in the summer and fall so I will keep in touch.