Th400 Diesel Conversion Vac Modulator Help

[adriner]

Ok, My knowledge of automatic trans's and diesels is low and I'm putting a 6.2 in my new truck which currently has a 350 gasser and th400, so what issues will I run into during the swap? Like anything with the tq converter, fuel lines, shift points in the trans, ect? (I'm really not kidding when I say I know nothing about automatics) Any knowledge will be appriciated, thanks!

 

[HotRodPC]

Hey Adam, Sorry about not responding to your PM. I read it about 4am one morning when I was sleep walking, never responded but it wasn't new anymore so I never responded. I forgot all about it until I seen this post.

I do believe on the 6.2's with Th400's the Vac Modulator line is connected to the vacuum pump. Be sure to use an adjustable modulator. Another thing guys will do is use an electronic vac modulator eliminator. Have no fear, it can be done. That's what is in all the CUCV Military trucks is the 6.2 and Th400. IIRC, there is a specific port for the Th400 Vac Modulator on the Vac pump itself.

 

[HotRodPC]

Also Adam, while on this topic, Transmission aside. How about you start a thread about your Gas Conversion to 6.2 Diesel Swap? We do have a category for that in Engine and Performance, Swaps to Diesel. As of yet, I don't recall that we have a swap to 6.2 from gas thread yet. Whether you know what you're doing already and it be a How To, or a mix of you do know and others adding advice. I think it will be beneficial to the forum if you'd do so. Here's a link to the that category.

http://www.gmsquarebody.com/forum/forumdisplay.php?f=50

 

[adriner]

Ok so does the trans being hooked to the vacuum pump determine when it will shift? Also about the tq converter will it work on my 6.2?

And I'll definaty start a thread, Mabye I can get opions while I'm in the process of the swap. I'm planning on starting next weekend!!! Hopefully

 

[Jims86]

Does the vac fluctuate with a vac pump?

 

[adriner]

Does the vac fluctuate with a vac pump?

I'd imagine so since it runs off the back of the cam

 

[Jims86]

I'd imagine so since it runs off the back of the cam

Ahh, ok. Would have to be a diesel specific modulator if vac increases with speed. Gas engine vac reduces as the throttle opens.

 

[Stroked]

We had this discussion awhile back on another forum and I believe it was a diesel specific modulator like Jim said.

Also, I'm pretty sure you'll need a different torque convertor specifically for a diesel.

 

[adriner]

We had this discussion awhile back on another forum and I believe it was a diesel specific modulator like Jim said.

Also, I'm pretty sure you'll need a different torque convertor specifically for a diesel.

I got another parts diesel with a 6 bolt tq converter but I think it was off a 700r. Will it work with my th400? Are the trans inputs the same?

 

[HotRodPC]

No No No. Most transmissions WILL NOT interchange Torque Converters. There is an exception to this rule however. TH and for those who don't know, when I use Th and sometimes Thm, it is for Turbo Hydramatic. So exception being, the Th350 and Th400 DO interchange torque converters. I do warn that it's Th350, not the Th350C, where the C designates Lock Up Converter. Th350 and Th400 DO interchange. Th350 and Th350C do not even interchange. So to answer your question directly, NO the 700r4 Torque Converter WILL NOT interchange with the Th400. I'm trying to think if any 6.2's came with a Th350 or not. I don't recall, but if you can find a Th350 Torque converter from a 6.2, then it will also work with the Th400 for a 6.2. In fact, I'd imagine is such an animal existed for a Th350 behind a 6.2, it would be the same exact part #. The other advantage to this is, if the Th350 never did come OE behind the 6.2 and you wanted to give it a try, then you could sure do so using the Th400 6.2 Torque Converter since it's backward compatible to the Th350.

 

[adriner]

Did all the military blazers come with a th400?

 

[Jims86]

Did all the military blazers come with a th400?

Me thinks so....HR, Retro?

 

[HotRodPC]

Yes, ALL the CUCV's came with 6.2, 400, NP208. There is one exception to that rule. The trucks that had a reason for a PTO, did come with NP205's. The Blazers came with 10 bolt coporate axles in 3.08 ratio. The 1.25 Ton trucks came with 4.56 ratio's, 14B Full Float Detroit Locker rear axles, Dana 60 front axles. A couple models with Lockers in the D60 also.

 

[adriner]

Yes, ALL the CUCV's came with 6.2, 400, NP208. There is one exception to that rule. The trucks that had a reason for a PTO, did come with NP205's. The Blazers came with 10 bolt coporate axles in 3.08 ratio. The 1.25 Ton trucks came with 4.56 ratio's, 14B Full Float Detroit Locker rear axles, Dana 60 front axles. A couple models with Lockers in the D60 also.

Well then I lied that extra tq converter I had, it was out of a military blazer (I thought some came with a 700r), well good then I can use it!!