Well,that was a waste of 15 bucks and time..

[diesel4me]

Tried changing the fluid in my TH350 to see if perhaps the filter was clogged,or if I could see anything wrong with the pan off--nothing wrong as far as I could see--valve body bolts werent loose,filter had ripped the brass screen out of its holder in 2 spots,but I see that quite often,not all clogged either--not much clutch material in the pan either,considering this tranny was used for plowing and has had some abuse...but after changing the filter and fluid,nothing improved--still no sign of reverse----I would have taken the valve body off,but decided against it--its bad enough trying to just change the filter lying on your back--you really need it up on a lift to do that kind of work,and I have never disected a tranny before--and after looking at the manuals,I dont think I would have much luck fixing it anyway--and it was a 40 degree drizzly day,so I wanted to get it back together before dark---guess the tranny must have a blown seal on the direct clutch--I think the clutch discs are ok,but there just isnt any hydraulic pressure to apply the clutch pistons and make reverse work....I've talked with a few local tranny guys here--they all say its the seals on the clutch pistons most likely--the weird thing is they say it should make a "whistling" noise while in reverse if fluid is leaking by the seals--mine is silent--I ran it for 15 minites in reverse with no noise,or any sign of reverse--its another "neutral"!!-The foreward gears still work(havent tried to see if third gear works,they also said if reverse doesnt work,usually third gear goes away too-)-after it ran out of gas,I was out of cash--so I guess the next thing to do is get my rolling "A" frame hoist erected again,and start cutting the truck up for scrap--I shouldnt have wasted my money and time on it--but I was hoping to get lucky--I still hate to cut up what was once my favorite"beater" truck for the past 15 years,but its really beyond ever being a good rig again,I might advertise it for parts first--its only going to be 20 degrees here the next few days,not exactly fine weather for cutting up a vehicle--I have another truck I'd like to buy,and cash is of the essence--the 80 dollar a ton scrap price means I could get about 300 bucks for whats left of it,after I save the bed,motor and transfer case--I'd save the 14 bolt SF 4.10 axle and front D44 8 lug,but the rear diff cover is rotted and leaky,and the housing is rusted pretty bad-not really worth keeping to me......And I need money for christmas and to maybe buy another truck I have my eye on--so I guess its RIP 74 K20

 

[big_truxx]

that sux!

 

[JK5]

I had a problem like you've been having...about 10 years ago..
Just before I pulled the trans..I got pissed..and did a couple neutral drops.

LOL...and that fixed it..
I must have had something sticking in the valve body.
The trans worked well for years...before I sold it.

 

[k20]

yeh when my th400 lost reverse, the first time i noticed it, seemed like i could increase throttle in 3rd and not pick up speed, then mash it alittle more, and itd start goin faster. Pulled in the yard, tried to back out after i washed the truck, no good, had to push it back so i could loop around and into the driveway.
Guy I took my trans to said it had never been rebuilt,(from the factory th400 has some seal he says you cant get the same style) and my 496 roasted the 17yo build.

 

[mountainexplorer]

I bought a truck once that had a bad TH400 in it. I towed it home, then tried to see what as left of it. It would go forward, but not back. I spent some time with it, and drove it around the block once, slipping all the way.

I got back to the house, tried reverse... and it still went forward. I put it in nuetral, and it still went forward. I figured, what the heck, I put it back in reverse, and drove halfway around the block going forward with it in reverse gear before it finally gave out all together and we had to push it back.

 

[dyeager535]

So did you try some of that tranny fluid that is supposed to help with problems like this? At this point I don't think $10 to try is going to hurt anything.

 

[99firehawk]

My tranny was making some cool noises in drive while stopped, SO me being the even headed anmd calm guy that I was. Did a few neutral drops and then brake torqued it for a few minutes, figureing if I was gonna pull the trans I was gonna do becasue it was broke not becasue it was noisey.
Well much to my dismay the truck laughed at my attempts to hurt it and I frustraded I walked away. Let it sit for 2 days went out there fired it up and its been quiet for the last 5k miles of so.

 

[mrk5]

So did you try some of that tranny fluid that is supposed to help with problems like this? At this point I don't think $10 to try is going to hurt anything.

Do you know the brand or anything? I'm ready to try it in mine. I was thinking about trying some of the stuff BG sells.


I'm really suspicious that something is stuck/sticking in my TH400. I've got a book at home about rebuilding transmissions. I'm going to look through it and I'll see if there is anything that might apply to your problem also diesel4me.

 

[dyeager535]

Nah, no idea, but I bought some powersteering stuff that said it helped with leaks, sure enough, it did stop leaking after a day or so later. (it does seem to take some circulating/penetrating time to work)

I think anymore that stuff is so common that any chain auto parts store will have it around where they have regular tranny fluid.

 

[diesel4me]

magical mystery oil

You must mean the Lucas transmission treatment stuff--I saw it at autozone and considered buying it for 8.99 +tax when I got the filter and dextron--but I had a feeling I was not going to have any success just changing the filter and fluid,and why waste another 10 bucks I really didnt have to spend on additives that probably wont work anyway--I'd rather put 10 bucks in the gas tank of the other truck I'm driving.
But I also see this new "Seafoam" line of products they are selling now,at lower cost--I've heard little about them,but the little I've heard is good,a few mechanics said the combustion chamber cleaner works good(I said so does a glass of water trickled down the intake!)--and there is "Trans Kleen"--"K-W Tranny treatment"--"Stop-Slip"and a bout 10 other miracle cures for whatever ails your tranny--I trust the Lucas brand--I have seen it work before in other junks!!--but I'll have to wait till I have the 10 bucks yo waste on a truck thats probably coming off the road unless the tranny comes back to life like some of yours did-Maybe a couple quarts of gas and a match down the dipstick tube would help.... .

I just spent the evening burning my eyes out of my skull reading the Want Ad book,dam fine print like a phone book,and about as thick as one too--there are over 2 dozen 4x4 trucks (GM) in just the "for parts" section alone,maybe 50 others similar to mine ranging from 500-1500 bucks--many with plows!!--there seems to be a lot of people selling their older trucks --like me,they probably have reached the "point of no return"--they dont want to fix them anymore,or spend money on them,probably short on cash this time of year like me,but there are some good sounding deals in there too--I might just wait before getting the sawsall out just yet--I might find a diamond in the rough,and be able to use some of my trucks parts to make another one--the truck I really want is the 89 K30 big block my friend is selling--theese others are just beaters I might buy and fix up for parts or use to plow,then sell later next year...I'm getting too close to broke to go too crazy buying trucks--of course ,since I havent much cash,there are a hundred trucks out there looking for a new owner,and hoping to escape the crusher--its really gone nuts here--I've never seen such a glut of used vehicles on the market,and the junkyards are crushing everything,and still overflowing with cars and trucks..pretty soon the 80's and older trucks will all be gone in short order--its already getting harder to find parts like a TH350 for a 4x4--I looked--3 huge yards have over 150 trucks in stock--only 1 TH350,in a rolling chassis that was burnt!--no thanks!!--all the rest had the 700R4,or 4l80 tranny--the TH350's are about extinct!--I have more at home(need rebuilding!)than they did!
I wish I had the money to buy a local salvage yard that my friend works at--its closing dec.31st--he's been there 20 years--its going to be hard this xmas for him,knowing his job is gone--and so will the junkyard most likely,since 10 yuppie homes will fit on its 19 acres(and it passed the EPA tests!)so it wont be long before its history--it was sad watching them crush 650 old packards,studes,and all the 50's and 60's cars and trucks--it was like a museum there,the last place around here with any old stuff left--many 20's and 30's cars were there--now its just a big empty feild with tires and rubbish scattered about--nothing sadder than the death of an old junkyard--I had some good times there--its all history now,but I guess such is life--full of dissapointments,and blown trannys----

 

[mosesburb]

That BG p/n 310 Transmission Conditioner works fantastic!! Around here we call it transmission in a can. I have fixed several customer's transmissions with that stuff. If a cure in a can exists, that is it.

 

[dyeager535]

I'm a firm believer that the stuff can't make things worse, ever since being in a bind when a hydraulic jack failed, (leaked, wouldn't develop pressure) and squirting it full of silicone, the only fluid I had around.

Didn't start working right away, (day or two maybe) but that was two years ago, and that jack still works like new, and doesn't leak a drop.

I've since tried silicone on hardened pieces (like the tail light gaskets) and sure enough, it does soften it up at least a bit.

Rubber seals in the tranny are what hold the pressure back to apply the clutch pistons, if they leak, they won't develop enough pressure to apply. Of course there are millions of things to go wrong in auto trannies, but a $10 can of stuff that seems to work extremely well, is a good bet IMO. If it doesn't work, you are out $10. If it DOES, then you've got a running vehicle again. Thats worth much more than $10.

 

[blazen86]

That BG stuff is awsome, Ive never heard a bad thing about it, but the good things people speak are pretty dag on good. I put it in mine

 

[diesel4me]

Who makes it??

Is BG the brand name,or part of the part #??--I listed most of the brands I've seen for sale here,but that one I've never heard of that one...I've seen Trans-Kleen(Siloo brand,now defunct,was good product line too),Marvel Automatic Transmission Treatment(by the folks who make Marvel Mystery Oil),The Lucas brand,various ones by Solder Seal(Trans-Fusion,Stop Slip,Leak-Stop),K-W brand tranny treatment,and the Dura-Lube and Slick 50 automatic tranny treatment,plus a few others like Berryman--but I dont recall seeing a "BG" brand line--maybe its a reigonal company,and they dont sell it here in the northeast???.


One of the tranny guys said I should have used synthetic tranny fluid,that it would help free up a stuck valve if thats the problem-( at 5 bucks a qt--yea,right!)-he just grunted when I mentioned stuff like Lucas,asking if he thought it would help a leaky seal build up pressure and make it work-- --I took that as a "no"!---he suggested brake fluid might swell and soften a hardened seal enough to make it work temporarily--but usually the seals crack,and fall into the case--then its hopeless,as is a cracked clutch piston,another common failure on TH350's he says...

I guess I'm willing yo try a "ten dollar cure"--whats ten when I have to pay the insurance tomorrow (130 bucks --cant even afford gas to drive it,or buy parts--but they get their money every month,while it sits--good racket,huh?)its like they hold it hostage!--chances are excellent I wont have any accidents--because its stuck at home!!.


The only thing about having the stuff actually work--I'll never be able to stop wondering when it will screw up again,when I'm miles away!!!

 

[468k5]

Try the sea foam, stuff works great for sticky valve bodies

 

[mrk5]

Is BG the brand name,or part of the part #??--

BG is the brand name. They make lubricants and addatives that are supposed to be the shiznit. They did a presentation for my hot rod club and it was pretty interesting. I've been using some of their stuff since. There's a couple of good ole boy hot rod mechanics in the club that swear by it, so I figure it must be pretty good.

Here's their website http://www.bgprod.com/

 

[surpip]

good lord 130 bucks for one truck? wow i have full coverage on the MINI, Blazer, and my motorcyle,3 speeding tickets, and renters insurance, and im ony paying 180 a month

 

[diesel4me]

Once,Twice,Three times the misery...

Actually its 130 bucks for the 3 trucks,the 82 K20.the 79 C10,and the 74 K20,so I guess its not THAT bad--but bad enough considering the fact they probably get driven 100 miles a month,only a few hours of road use per month--the odds of the insurance company having to pay out any money for an accident are definately stacked in their favor when the trucks sit in the yard most of the time-( or in a parking lot for 8 hours while your working)-I think insurance is a rip off--for the amount I've spent on it,and never had an accident,or filed a claim in 15 years--I could have retired on that much money!--I realize its nessasary,but it sucks when all you have is compulsory,and it only protects the "other guy"--and that 130 bucks a month would buy a lot of gas and parts...... But thats another subject for another thread I guess.....

 

[mrk5]

Oh, and I was going to mention that the Advance Auto Parts and Carquest here in town sell the BG stuff.