If you don't find anything when you pull the pan, I would start asking around at local parts stores for someone who rebuilds GM transmissions. With any luck you can find someone local to help you better. Good luck and keep us posted.
CK5
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TH400 has no gears
- Thread starter nad
- Start date
It sounds fishy,that you'd have good shifting and no slippage,then "lose" all the gears..to me that indicates a valve body problem,something isn't letting the fluid get to the clutch packs and engauge them..sometimes the pressure regulator valve thats under the valve body sticks and wont allow sufficient pressure to the clutches...extremely low fliud levels can do it also...the noises might be the pump whining due to it being run low on fluid or the pressure regulator valve ,or even fluid trying to be pulled thru a clogged filter...
I had a TH350 that refused to go i any forward gears after a cold start,especially if the truck sat overnight--I'd have to wait for several minutes until the engine warmed up for it to engauge any forward gears,once it finally went into gear,I could drive it anywhere and it would shift perfect,no slippage,etc..I tried every tranny additive sold at the time,to no avail--even followed one old tranny rebuilders advice and added a small bottle of Lestoil to the fluid (yes,Lestoil!--he claims it works better to free up sticky valves and varnish than many store bought additives,and assured me it wouldn't hurt it any)--didn't have much to lose anyway,so I tried it--it did cut down the length of time I had to wait for drive to appear every morning,but I eventually swapped a SM465 into the truck,before I lost my job from being late so often every morning...I suspect the TH350 had some hardened rubber seals that let fluid leak by until the warmed up some ,then let the forward clutch apply..
I would try testing your line pressures before doing much else--there are little pipe plugs on the side of the tranny case you can hook up a test gauge too,and yourun the engine and jack up the wheels and put it in the appropriate gear and read the pressures at a specified RPM,that tells you if the pump is putting enough pressure out,and the pressure regulator valve is working,and if any servos or clutches are not receiving sufficient pressure..you'll need a tranny service manual to find the plug locations and the proper procedure to check it out,the specs for the pressures at certain rpm's,etc..
If the truck sat a long time there might be some water in the tranny from condensation,and it wont take much rust on a valve or other internal part to cause this kind of intermittent problem..adding some Lucas tranny treatment to the fluid after changing it might help,I've seen it revive some "dead" trannies before ..
I had a TH350 that refused to go i any forward gears after a cold start,especially if the truck sat overnight--I'd have to wait for several minutes until the engine warmed up for it to engauge any forward gears,once it finally went into gear,I could drive it anywhere and it would shift perfect,no slippage,etc..I tried every tranny additive sold at the time,to no avail--even followed one old tranny rebuilders advice and added a small bottle of Lestoil to the fluid (yes,Lestoil!--he claims it works better to free up sticky valves and varnish than many store bought additives,and assured me it wouldn't hurt it any)--didn't have much to lose anyway,so I tried it--it did cut down the length of time I had to wait for drive to appear every morning,but I eventually swapped a SM465 into the truck,before I lost my job from being late so often every morning...I suspect the TH350 had some hardened rubber seals that let fluid leak by until the warmed up some ,then let the forward clutch apply..
I would try testing your line pressures before doing much else--there are little pipe plugs on the side of the tranny case you can hook up a test gauge too,and yourun the engine and jack up the wheels and put it in the appropriate gear and read the pressures at a specified RPM,that tells you if the pump is putting enough pressure out,and the pressure regulator valve is working,and if any servos or clutches are not receiving sufficient pressure..you'll need a tranny service manual to find the plug locations and the proper procedure to check it out,the specs for the pressures at certain rpm's,etc..
If the truck sat a long time there might be some water in the tranny from condensation,and it wont take much rust on a valve or other internal part to cause this kind of intermittent problem..adding some Lucas tranny treatment to the fluid after changing it might help,I've seen it revive some "dead" trannies before ..
nad
1/2 ton status
Yeah, I let it warm up to normal temps, left it running for like 30 minutes after I put fluid in it, and it still won't go into gear.
Tried it again tonight, just to see if maybe magic happened sometime in the last 24hrs, and still nothing.
Looks like I'm dropping the pan Sunday afternoon. Ugh, it's cold here, and the truck is parked in the mud. This is when I wish it was 4WD, getting underneath it is a pain.
Tried it again tonight, just to see if maybe magic happened sometime in the last 24hrs, and still nothing.
Looks like I'm dropping the pan Sunday afternoon. Ugh, it's cold here, and the truck is parked in the mud. This is when I wish it was 4WD, getting underneath it is a pain.
bronc3buster842001
1/2 ton status
nad
1/2 ton status
A K30 dually? Problem is I'm broke, and wanting to sell this one, but not gonna get much from it with a broke tranny. Wish I had the money for a K30 
bronc3buster842001
1/2 ton status
Last i knew he only wanted like 3 grand for it. He might even do some trading with ya.
Loosen the pan as suggested in an earlier post, then the filter pickup tube should be attached to the valve body with one bolt through the center of the filter, and a tube that goes up into the trans case at the front. See if it is in place as described like this:
If not, start with a new filter, and make sure the O ring is on the tube and it is pushed up into the case firmly in the hole on the upper right in this pic:
and
then put the shouldered bolt back through the center of the filter. Also check the shift rod to see if it is actually moving the valve body control valve. Check it with the filter off, it will be easier to see. If this don't get it, try the pressure test as recommended above if you can. If not, time to take it out and start seeing whats wrong in there. An auto trans alot of times will tell you what is wrong with it when you start taking things apart.
If not, start with a new filter, and make sure the O ring is on the tube and it is pushed up into the case firmly in the hole on the upper right in this pic:
then put the shouldered bolt back through the center of the filter. Also check the shift rod to see if it is actually moving the valve body control valve. Check it with the filter off, it will be easier to see. If this don't get it, try the pressure test as recommended above if you can. If not, time to take it out and start seeing whats wrong in there. An auto trans alot of times will tell you what is wrong with it when you start taking things apart.
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nad
1/2 ton status
Thanks for the illustration, at least now I kinda know what I'm looking for. I'll let you know what I find, won't have time to pull the pan until Sunday. Wish it was driveable, I'd move it into the garage and do it.
nad
1/2 ton status
Well it's way too damn cold outside for me to be doing anything on the truck today. But I did go outside and start it once, and as soon as I started it, the pump made that whining noise for about 30 seconds, then stopped. Then I put it in gear, and IT MOVED, R and D both worked!! Then I put it back in Park, checked the transmission fluid, then tried going back into gear again, and NOTHING.
I put some Lucas transmission valve lubricant in it to see if maybe that will free something up. I just think it's odd that it works sometimes, then suddenly doesn't....
Does this signify anything else? Before I pull the pan, I just want to make sure I'm not wasting my time, when it's something more simple, or more complex, than just the pickup tube/filter.
I put some Lucas transmission valve lubricant in it to see if maybe that will free something up. I just think it's odd that it works sometimes, then suddenly doesn't....
Does this signify anything else? Before I pull the pan, I just want to make sure I'm not wasting my time, when it's something more simple, or more complex, than just the pickup tube/filter.
wasted wages
1 ton status
I bet it's one of these:
1) low on fluid
2) filter is plugged up.
3) filter fell off.
4) front pump is failing or there is a internal leak....
I would just dump in 1 or 2 more quarts...crank it up and see if it moves...if it does, pull it into the shop and drop the pan...
if the filter is in place and not plugged...I would bet it's rebuild time....
1) low on fluid
2) filter is plugged up.
3) filter fell off.
4) front pump is failing or there is a internal leak....
I would just dump in 1 or 2 more quarts...crank it up and see if it moves...if it does, pull it into the shop and drop the pan...
if the filter is in place and not plugged...I would bet it's rebuild time....
nad
1/2 ton status
Well I'm 99% sure it's not low on fluid, because I've put about 1.5 quarts in it plus another quart of Lucas stuff. It's reading full on the dipstick. Good idea, I'll try it again tonight and if I can get it to move, I'll drive it straight into the garage.
I just don't see how a filter like that could get plugged up.
I just don't see how a filter like that could get plugged up.
Well I'm 99% sure it's not low on fluid, because I've put about 1.5 quarts in it plus another quart of Lucas stuff. It's reading full on the dipstick. Good idea, I'll try it again tonight and if I can get it to move, I'll drive it straight into the garage.
I just don't see how a filter like that could get plugged up.
It sounds to me like sticking valves in the valve body, but I am no expert.
I would definitely try and get it to move and get it to the shop and pull the pan and see.
And you'd be amazed how this filter can get plugged.
Most of the time some moisture gets in there and creates a film of sludge and blocks the screen completely.
That whining sounds like a pump, but it does sound like the valve body problem to me also. if you can get it in gear again, 1st priority...get it to the garage. If you make it there...jack up the rear on secure jackstands and warm up the drivetrain, including rear axle. Once its warmed up try putting it in gear again, if it moves let it idle there for a minute or two, then drop it through the gears to see what happens. If it still moves, drop it into reverse to quickly change fluid direction within the valvebody. See what happens.
nad
1/2 ton status
Got it moving, got halfway up the driveway, then it quit. Stuck halfway blocking the street. My neighbors hate me. Now I'm waiting for a tow truck, just gonna have it towed to the shop and have them look at it tomorrow. I'm about done with this 73-87 Chevy game. Too much money, time, and breakage for me.
I think he failed us.
I thought he was more determined.
Well I am just kidding, some people enjoy fixing things, some people just enjoy driving them, if he's getting too much trouble with it and he just wants to drive it then he should just go to a shop and get it fixed and then sell it.
nad
1/2 ton status
I didn't give up on anything. Just got frustrated to the point that I didn't know what else to do. Having a 10,000lb truck stuck on the middle of a main road that's on a hill in front of your house, and having nothing else to try pulling it with was just overwhelming. Tried pushing it uphill, obviously that wasn't going to happen. On top of it, it was about 25*F outside, so that added to the frustration.
Had a tow truck come get it and take it to the shop right down the street. Got the pan pulled down today, filter and pickup tube are in place. Looks like the front pump died and caused the tranny to fry.
Anyway, the guy that works at the shop has a buddy that works at a tranny shop that's gonna do a full rebuild for $200 plus the cost of parts. So we should have the trans out tomorrow then off to the transmission shop it goes to get rebuilt. Total cost is gonna be something like $500. Not too bad for a full rebuild at a shop.
Thanks for all your suggestions guys, was really hoping it was gonna be something simpler.
Had a tow truck come get it and take it to the shop right down the street. Got the pan pulled down today, filter and pickup tube are in place. Looks like the front pump died and caused the tranny to fry.
Anyway, the guy that works at the shop has a buddy that works at a tranny shop that's gonna do a full rebuild for $200 plus the cost of parts. So we should have the trans out tomorrow then off to the transmission shop it goes to get rebuilt. Total cost is gonna be something like $500. Not too bad for a full rebuild at a shop.
Thanks for all your suggestions guys, was really hoping it was gonna be something simpler.
Im glad you decided to rebuild the 400.
Alright Nad, I thought pump when you said whining....that ain't good usually, since it rely's on pressure to make it work.
200+ parts is ok, the pump will be about as much as a rebuild kit for it, so your doing alright. Just think a 4L80E is like ~2500$ rebuild
200+ parts is ok, the pump will be about as much as a rebuild kit for it, so your doing alright. Just think a 4L80E is like ~2500$ rebuild
