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Discussion Starter · #1 ·
was plowing town road with 1984 military(m009).truck is fairly healthy and runs good untill today.the turbo 400 quit.i knew it was running hot as the snow was pushing hard.suddenly no movement in any gear.no noise.sight smell of bad trans fluid.shut everything down and wait 15 minutes.start back up and truck tries to move,but i know things are wrong.shut down and got towed back to highway garage.let sit for 6 hours.started and moved normally.did not drive on the road yet.fluid is blackish tan but clear and has that slightly cooked smell to it.should i pull it out or is there any hope for it.i'll be pulling the pan tuesday and checking for debris.
 

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started and moved normally
If it were me, I would change the fluid and try it. I don't know much about transmissions, but I do know that I wouldn't scrap the trans if the truck still moves.

Somebody else who knows more about transmissions may have more thoughts on this.
 

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If your plowing again with it I would suspect it will fail again. Flush and normal driving it might work.
 

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drain and add a tranny cooler. remember not all tranny fluid will be drained out, alot stays in the torque convertor.
 

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Do like I do. Pull one cooler line off radiator. Over fill trans. Crank and run till clean fluid comes out. Bubbles appear shut off, add more fluid and run again. This will flush fluid out of convertor and lines.

You can also do this as preventive maintance without pulling pan. I sometimes do this before a long hard pull. Fluid is cheap, trans, not so cheap.

Change fluid every 24,000 miles or two years which ever comes first.

Like the red, white , and blue.
 

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Discussion Starter · #6 ·
well guys i thank for your input,but i think its rebuild time for the 400.got called in to work on another town truck whose rear duals were only being held on be 2 very loose nuts.anyhow i took the pick-up in question out for spin.lazy going into gear,stall speed seems to have increased.second gear is very mushy.no high gear(3rd).turn around go back to garage and now things have got worse(everything warmed up now)needs alot of coaxing to move.i think its done.
 

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having torn down enough of these THM400 over the years, you can certainly run it until it doesn't move anymore or you can pull and rebuild while the hard parts are still rebuildable. the "high element" drums are starting to become harder to find and you need as many clutch elements you can cram in a drum for these diesels. Pull it and pray that the drums didn't get torched.
 

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I think the rebuild is on the right track. In my experience when fluid is toast so is trans. a cooler is a must. I have seen alot of different things used for coolers . ac condensers ect. new or old flush cooler and blow out before installing.If you have trans rebuilt make sure and have old oil cooler flushed to get ride of contamination. if the contamination is not from outside (water or mud) I have never changed filters or fluid between rebuilds on our auto's here . if the filter is plugged with shavings chances are trans rebuild time. I get at least 100,000 on trans before rebuild. If it has a transfere case we use low range on hard jobs . trans. temp gauge may save you next time it is amazing to see how fast temp. can spike. of course this is my opionion.
 

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My Dad has 82 chev 1 ton with 6.2 and 400 turbo. he uses it on the farm, had a sprayer in the back. he was replacing the transmission once, sometimes twice a year. until finally the transmission shop suggested installing a heavy duty torque converter from allision. hasn't had any problems since, been almost 10 years. transmission shop guy was pretty sure it was the torque converter that was wearing out and sending metal shavings into transmission and tearing it up. seems as though he might have been right.
 

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The "Allison" is referred to as an AT275 in some aftermarket rebuilder catalogs. I'm not familiar with the Allison's involvement but I believe it was part of their design for their own H.D. convertors. I've used it for years with good success. It's more of a "Hot Rodders" convertor without the high stall speed usually associated with race parts. It has the usual "blah, blah, blah" stuff. Furnaced brazed fins, H.D. bearings, thicker bushings, special machining where needed, H.D. sprag unit, anti-balloon plate, H.D. welded lugs, beefed up, modified, etc.

Indeed, a good piece for any AT400 that's doing heavy pulling. Last one I purchased was a bit over $260. Wello worth it. I've never had one fail. Not the case with stock type, light duty rebuilt convertors.
 

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I have a 86 Chevy K10 pickup with a 700R4 and 3.08 gears, would the AT275
converter work? What do you suggest?
 

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The aftermarket builds the same beefed up convertor with all the same features for the 700. I have on in my suburban and have sold several to customers that I have built transmissions for. No problems yet. (knock, knock, knock on wood)
 
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