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What is the correct transmission dipstick length for TH400 transmission?

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Ancient4X4

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So I have a 1977 K10, TH400 transmission, and years ago I lost the transmission dipstick. I found a used one at a junkyard a long time ago and it seems to fit fine, but it doesn't stay in place, it always pops up and sticks out after driving awhile. So I decided to order a new one from JC Whitney a few years ago and it was way shorter than the junkyard replacement one I have in the truck. There's no way this one was going to register any tranny fluid. So I kinda forgot about the entire thing and it's been laying in the garage ever since as I figured I ordered the wrong one and don't drive the truck very often.

Fast forward to last month, I decided to order an OEM replacement from Classic Auto and it comes in. It's the same shorter length as the JC Whitney one. I call them up and the operator said that the correct length for TH400 is 24 1/8" and TH350 is 27 1/8". So I'm wondering if I have one for a TH350 in the truck right now. The end of the junkyard one looks like the tip might be broken off though, I can't tell. Hard to believe I'm running 3" or so low on tranny fluid all this time, but maybe that's been the case. I don't want to overfill it. Anyone else have a TH400 or TH350 they could measure the tranny dipstick on?
 
Do yourself a favor and get one from the dealer. Somewhere in the later 80’s GM started using a locking dipstick that has a flip lever that doubles as a pull handle. This type is far better than the earlier pull ring design.
 
My 1998 S-10 Blazer has that style dipstick from the factory.

Chevy makes one like that they sell for a 1977 K10 truck? I can buy it at a Chevy dealer? I have trouble finding anything for this old truck.

The original transmission dipstick that came with the truck never popped out like this replacement junkyard one always has.
 
GM made on later model trucks so you’ll have to use something other than your 77. Try an 88-90 V3500 with an automatic.

The junkyard stick probably pops out because the seal is worn out.
 
Yea, I'm not really concerned about it that much. I already have three, I don't plan on buying a fourth. The reason I posted this thread is that I just want to know if the other two are the right length and if I need to add transmission fluid.
 
Ancient4X4 said:
Yea, I'm not really concerned about it that much. I already have three, I don't plan on buying a fourth. The reason I posted this thread is that I just want to know if the other two are the right length and if I need to add transmission fluid.
Click to expand...
I will try to find mine and measure
 
First off are you sure you have a T-400 ?
Is the pan square shaped or Texas shaped ?

Second- No matter which trans you have, the dipstick should not be popping out by itself.
Either it's overfilled, or the case vent is plugged.

Third- The dipstick tube should not be coming out of the case, unless the tube is not fastened to the bellhousing properly.

IIRC- There are two styles of sealing o-rings. one type of oring that fits on the tube itself, and another type that looks like a tophat. It fits in the case and then the tube is inserted into the seal. but both require that the tube be properly bolted to the bellhousing to hold it in place.
 
I have a TH400 from a '74 Monte-Carlo that had a factory 454--both the dipstick & tube on that one is way shorter than the one on my '82 K2500's TH400...
The stick in my truck had the top "cap" come off and the pull ring was somewhat straightened out--made it tough to tell the exact amount of fluid that was in it..

I got lucky,a friend happened to have 3 TH400's and a shed full of spare parts,he had a like new tube & dipstick from a K series like mine the same length ,sold it to me for $5--I only used the stick though,figured I'd wait till the tube got rusted enough to leak, to go thru the agony of replacing it..
..you'd be hard pressed to find one used at a salvage yard here now,few square bodies are in them here any more,the few that are,are just stripped out shells..

I had a '67 Impala with a powerglide ,the dipstick broke off evidently before I got the car,only the top part with the handle and about 6" of the stick remained..never did find a replacement for it..
I was told by a transmission shop who promised to get me one (and never came thru!),to just add fluid until it spewed out of the overflow,it'd "find its own level" eventually..so I did just that..on dirt though,not in the driveway..car almost caught fire so much ATF sprayed on the exhaust !..:eek:
 
wasted wages said:
First off are you sure you have a T-400 ?
Is the pan square shaped or Texas shaped ?

Second- No matter which trans you have, the dipstick should not be popping out by itself.
Either it's overfilled, or the case vent is plugged.

Third- The dipstick tube should not be coming out of the case, unless the tube is not fastened to the bellhousing properly.

IIRC- There are two styles of sealing o-rings. one type of oring that fits on the tube itself, and another type that looks like a tophat. It fits in the case and then the tube is inserted into the seal. but both require that the tube be properly bolted to the bellhousing to hold it in place.
Click to expand...
The biggest thing is to get the matching tube and stick.
If the tube fits the case then the stick is correct.
I believe the stick will be poking through the end of the tube by 1"
 
The original tube is attached to the engine. The old dipstick is on the right of the three in the second picture. This is what I'm trying to figure out and why I keep getting the wrong part.

 
So anyone else have the same thing with their truck? Anyone know where I can order the correct part?
 
there are too many different tubes and sticks for the same transmission. I saw it for myself at the junkyard when I asked for just a Stick, Dude showed me a bunch of TH transmissions all with various lengths tubes. just buy a tube with stick
 
Thanks for the reply. It makes me wonder why there are so many different sizes, but only one seems to be offered everywhere as the length for TH400.

Especially the second one which didn't even come with a tube!
 
Ancient4X4 said:
Thanks for the reply. It makes me wonder why there are so many different sizes, but only one seems to be offered everywhere as the length for TH400.

Especially the second one which didn't even come with a tube!
Click to expand...
I will help you get this right.
If you have a tube that fits right, I will get you a picture of the stick in the tube showing how far it sticks out and give you a measurement of that stick out.
That is the only thing that does not change.
Tubes can be brought further back or forward so they make a stick to match it.
That's why it gets confusing.
I will try and get you that tonight
 
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