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Are there any differences between 700r4's that were in gas trucks vs. diesel trucks? I have a line used ones of both. The guy with the diesel one said his has a gas torque converter. Is there anything I would have to swap between the two?
 

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hidesertwheelin;1599407; said:
Are there any differences between 700r4's that were in gas trucks vs. diesel trucks? I have a line used ones of both. The guy with the diesel one said his has a gas torque converter. Is there anything I would have to swap between the two?
The torque-converter for the diesel is designed with a different torque-curve. Other than that, the transmissions should be the same - as long as the gas-transmission came from a V-8 - and NOT a V-6 -or a four-banger. You can tell by the ID code on the rear of the trans.
 

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I don't deal with transmissions much, but I've been told that the valve body is different on the diesel 700r4 compared to gas. Maybe somebody can tell us if that is true.
 

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I have been told there's no difference between the gas and diesel 700's other than torque converter. I recently had a V6 700R4 built with the upgrades and the hydraulic lockup feature for a 350 V8 that I was going to put into the '68. When the THM400 died in the bus, I decided to swap it into that instead. I asked the guy that built the tranny if I could expect any problems. As long as I swapped the gas TC for one for diesel, he said he would honor his warranty on the tranny. That was good enough for me. Only about 3000 miles so far, no problems.
 

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I don't know for sure whether or not there was a difference between the gas and diesel transmissions, but I do know that if there is a difference it is minimal.

In my opinion, the torque converter isn't the biggest thing. I ran gasser torque converters behind my diesel and they worked fine. They're probably a bit different, but that isn't going to be the thing you notice. The thing that really makes the noticeable difference between a gas and diesel transmission is the way the governor is set up... If you don't adjust the governor to work with the diesel the shift points are going to be too high. I drove mine a little bit with the gasser governor setup and it ran all right but the engine raced so much the truck sounded like a city bus, which was kind of cool (although a little annoying and uncomfortable)...

That said, governor adjustments are easy. If you keep your old transmission you could just pull the governor from that if you didn't want to mess with it, but if you don't you can just pull the governor out and set it up the way you want it. You would need a governor adjustment kit (which you can buy from any tranny shop) to do the adjustment.
 

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The valve body configuration is slightly different between gas and diesel 700r4's. The pressure switches can be changed around to match the tranny you currently have. In my experience, the diesel torque converters tend to hold up better than the gas torque converters. Converters tend to have a high failure rate. Other than that, make sure you change the governor like high sierra 2500 suggested and make sure to propperly adjust the tv cable. The later the model of 700 trans, the better with the best being 87 and later. They have totally different valve bodies.
 

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hidesertwheelin;1599407; said:
Are there any differences between 700r4's that were in gas trucks vs. diesel trucks? I have a line used ones of both. The guy with the diesel one said his has a gas torque converter. Is there anything I would have to swap between the two?
I assume that many people choose a 6.2 diesel because of it's low RPM torque characteristics. It is also a low RPM engine, as compared to a gas engine. Subqequently, the torque-converter is custom-tailored to the diesel including torque-curve and stall-speed. So, yes, a gas coverter will fit and run the vehicle -but it will NOT take full advantage of the torque-curve of the 6.2. I cannot think of a single good reason to go through the labor involved and intentionally install the wrong converter.

I also assume, but do not know for sure - that GM doesn't make torque-converters specifically for diesels. I believe they are all rated by a set of four basic characteristics - and engines get converters that match their performance. When the 305 gas engine was created, it was designed to provide a lot of low RPM torque - similar to a diesel - because it was given a very long stroke as compared to it's bore. The 6.2 diesel - was designed to be very close to the 305 gas engine (close, but not the same). So, it's possible that some 305 gas converters are close to the same a 6.2 converters.

The best way to tell is the tag on the converter. The numbers or letters tell the story - and the second letter in the sequence is the stall-speed rating.

G,H,K = 1200-1400 stall-speed

E,F,L = 1611-1654 stall-speed

B,C = 2000 stall -speed





 

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I can think of one good reason to install a gasser torque converter... Because you are out of money and need you truck to run so you can make some more money and all you've got is gasser stuff to work with. No, it doesn't take full advantage of the diesel torque curve, but it does get you down the road if that's all you've got to work with. My point is that if you're in a bind the gasser converter will work, not that it works the same as the diesel converter.
 

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High Sierra 2500;1600368; said:
I can think of one good reason to install a gasser torque converter... Because you are out of money and need you truck to run so you can make some more money and all you've got is gasser stuff to work with..
Well yeah . . . you could use that sort argument to do just about anything. When I said "good reason" I think I put it into proper context.

If I was stone broke - and had nothing else to drive - of course things would be different.

Considering you can buy a newly rebuilt torque converter for $100, and your labor time is worth anything to you, and driveability is also - I can't come up with what I call a good reason. But, I'd say the same to putting a used converter of any type back in. It is one of the few components you cannot take apart and visually inspect - unless you want to cut it into pieces.
 

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I definitely agree. If you aren't completely broke there's no good reason to use the wrong converter...
 

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Discussion Starter #11
This is the tranny I'm looking at. Does anyone know what these number mean?





 

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jdemaris;1600399; said:
Considering you can buy a newly rebuilt torque converter for $100, and your labor time is worth anything to you, and driveability is also - I can't come up with what I call a good reason. But, I'd say the same to putting a used converter of any type back in. It is one of the few components you cannot take apart and visually inspect - unless you want to cut it into pieces.
Where can you find a rebuilt torque converter? Do you have a link? I am in the market for one
David
 

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good start...

Hidesertwheelin...good to know your starting with a K model 700-r (obviously indicated by the large cast letter k on the housing).IIRC the k models have cases that are a little thicker than the non k models.if you can,pick up the inspection cover that matches this model trans,as i don't see it in your photo's...the covers for the k models are cast aluminum,rather thick compared to the stamped ones,and add strength to the case when it's all bolted up.

can't tell you what the numbers mean.as for the converter...personnaly i'd never reuse one unless i had a good idea where it's been,and the life it's been leading.iv'e seen used converters cut apart,and you would not believe the crud and busted parts that can hide in there.if your broke,run it.if your not,it's money well spent.
 

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djw32;1601393; said:
Where can you find a rebuilt torque converter? Do you have a link? I am in the market for one
David
I'm not a transmission expert, I only fix them on an ad hoc basis. So, there are probably people that know of better buys then I do. That being said, I usually buy my transmission parts from Makco. The link follows. Also general autoparts stores like www.partsamercia sell them pretty cheap also.

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=4L60-700R4tc
 

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The only difference between the gas and diesel is the flywheel and torque converter. The diesel torque converter uses 6 bolts to the flywheel the gasser uses 3 bolts.
 

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As I recall only early diesel 700R4s had six lugs while later models had only three like the gassers... I might be wrong, though...
 
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