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TH400 Question

daleearnhardt01

daleearnhardt01

1/2 ton status
Joined
Aug 29, 2002
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Location
Richmond, VA
Have a 400 that has a little issue. When I manually downshift it into 2nd it will not hold the gear and help decelerate the truck, it just free wheels. Holds the gear just find under power and downshifts by itself when stood on and holds just fine.

Any ideas? It is a relatively new transmission, just swapped into my K5. It is not a stock build either FYI.

Like I said its working great otherwise, when I want the truck to go and pull it down into 2nd it downshifts and goes on up the road just fine...
 
Sleeper 2nd huh (neutral until your on the gas). Ive had a few th350's and th400's do this and could never figure out what the deal was even after thousands of miles. Im assuming its a valve body related issue, but i hope someone will chime in that delt with this before and actually fixed the issue.
 
If i'm not mistaken it is the one way rollers in the sprag that are causing your issues.
 
I'm not a tranny guy but i'm starting to have the same issues and my trnas guy told me this is what's causing it. I'm not going to worry until something breaks and even then i won't worry since i don't pay for trans rebuilds. :D
 
Normally, when in "D" range, a sprag prevents the forward drum from rotating under acceleration and lets it freewheel during decel. When you shift into manual "2" range the tranny should apply the front band, which prevents the drum from turning under both accel AND decel.

In other words, it sounds to me like your front band isn't being applied in the manual "2" range....
 
TH400 No engine braking in D2 range ( manual 2nd gear)... can be one of two things...
-Front servo & accumulator- oil rings and/or bores leaking, or front servo piston cocked or stuck in the bore, damaged piston seal, or pin, (or mis-assembled or wrong parts)..
-Front Band- broken, burned, not engaged on anchor pin, and/or servo pin.
 
4X4HIGH said:
I'm not going to worry until something breaks and even then i won't worry since i don't pay for trans rebuilds. :D
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just keepin your fingers crossed you're not on a road trip when the ol slush box gives out?

my tranny guy, and my mechanic warantee parts and labor for life! ... on the spot!
 
Ryan B. said:
just keepin your fingers crossed you're not on a road trip when the ol slush box gives out?

my tranny guy, and my mechanic warantee parts and labor for life! ... on the spot!
Click to expand...

I know enough people with trailers that it shouldn't be an issue if i break on a "road trip".
 
4X4HIGH said:
I know enough people with trailers that it shouldn't be an issue if i break on a "road trip".
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I don't understand that "logic". TH400's are easy and cheap to work on. It makes no sense to ignore the problem. Granted, a front band issue isn't going to leave you stranded, but still :what:
 
MaxPF said:
I don't understand that "logic". TH400's are easy and cheap to work on. It makes no sense to ignore the problem. Granted, a front band issue isn't going to leave you stranded, but still :what:
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The "logic" is that if my rig breaks and i can't drive it anymore i know enough people with trailers to come rescue me and get me back home. Once i'm back home i can get a trans rebuilt for free. Since i'm not a trans guy there is no doing it myself. Also my rig has a 700R4 and not a much easier to rebuild TH400. My expertise is engines. I could easily tear one apart on the side of the road and repair it (assuming i could get required parts).
 
If you can rebuild a motor you can rebuild a 700R4... they are a piece of cake to figure out. Something like an E4OD is where you start to get complicated.
 
kennyw said:
If you can rebuild a motor you can rebuild a 700R4... they are a piece of cake to figure out. Something like an E4OD is where you start to get complicated.
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E4DOA's aren't any more complicated than a 700 or any other auto tranny. They might have more parts, but it's all the same basic stuff.
 
MaxPF said:
E4DOA's aren't any more complicated than a 700 or any other auto tranny. They might have more parts, but it's all the same basic stuff.
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I was referring to the special tricks you have to know to get it together right and the electronics that control it all (that usually have to be replaced as well but a novice will overlook). Luckily when I was messing with them I was able to get advice from a pro tranny guy where I was buying my hard parts.
 
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