# 2nd gear slipping. TH400



## Charlie Ashby (Aug 23, 2018)

Rebuilt my motor and put everything back in. 

Car runs great but I can't shift into 2nd manually. It just revs up. When driving and it shifts by itself, it will go into 2nd but I can feel it still slipping. I replaced oil and filter and module to see if it was that easy, but no luck. 

You guys think it is the sprag? It was fine before i pulled the motor. But now just doesn't go into 2nd manually and just slips. 

What do you guys think?


----------



## BearGFR (Aug 25, 2008)

I'm not that versed on TH400's, but something's amiss. Make sure the fluid level is correct, that you don't have any leaks in the vacuum line to the modulator, etc. You might also pull the modulator and examine the bit of fluid that will drain out to see if it looks brown or smells burnt. If that's the case it's a sign of internal problems.

Bear


----------



## Charlie Ashby (Aug 23, 2018)

Fluid is good and new. Vacuum line and modulator are new as well. 

If i am in 3rd gear driving and go WOT, it does kick down to 2nd gear and pulls like hell. No slipping. If i am cruising at light speed or coming to a stop and manually shift to 2nd, it does absolutely nothing. Almost goes into neutral.

I do have a squeal noise if i floor it real quick. It happens for a few seconds. Also happens if I am in park with the hood popped and snap the throttle from the carb. Sounds like a belt but can't tell.


----------



## BearGFR (Aug 25, 2008)

That's a strange one. So it acts like it's going into neutral on upshifts but works fine on downshifts? That makes me suspect a problem in the valve body, servo, piston, hyrdraulic passage, etc that doesn't fully apply the second gear clutch on upshifts. This is a problem for someone who knows way more than I do. 

Bear


----------



## Charlie Ashby (Aug 23, 2018)

The opposite of what you said 

Up shifts fine, down shifts fine under WOT throttle with the kick down and 2nd gear pulls. 

I just can't manually shift into 2nd without it feel like its just slipping. Also, slowing to a light i dont here it downshift into 2nd either.


----------



## BearGFR (Aug 25, 2008)

So it's only on manual shifts? Sorry for misunderstanding. In that case, if start with the cable adjustment. At the point where the cable connects to the transmission, there's a slotted adjustment point.


----------



## Charlie Ashby (Aug 23, 2018)

it will actually shift into that gear but the gear slips. 

basically 2nd gear is slipping and not acting properly.


----------



## Bob Young (May 27, 2018)

Charlie Ashby said:


> Fluid is good and new. Vacuum line and modulator are new as well.
> 
> If i am in 3rd gear driving and go WOT, it does kick down to 2nd gear and pulls like hell. No slipping. If i am cruising at light speed or coming to a stop and manually shift to 2nd, it does absolutely nothing. Almost goes into neutral.
> 
> I do have a squeal noise if i floor it real quick. It happens for a few seconds. Also happens if I am in park with the hood popped and snap the throttle from the carb. Sounds like a belt but can't tell.


Suggestion to check;

For grins, un-bolt the torque converter from the flex plate and see if it moves back away from the flex plate about 1/2". If it's tight to the flex plate it did not seat into the front pump. That will cause problems and can cause a squealing noise. Just figured since it was working before and now you have a problem, might be the torque converter did not get back in the right slot. Good luck.


----------



## Charlie Ashby (Aug 23, 2018)

Bob Young said:


> Suggestion to check;
> 
> For grins, un-bolt the torque converter from the flex plate and see if it moves back away from the flex plate about 1/2". If it's tight to the flex plate it did not seat into the front pump. That will cause problems and can cause a squealing noise. Just figured since it was working before and now you have a problem, might be the torque converter did not get back in the right slot. Good luck.


Once I bolt it to the flex plate, wont it come right back forward again?


----------



## Bob Young (May 27, 2018)

Yes, but the idea is that the slots in the torque converter align with the teeth in the pump. You can have the torque converter pushed on top of the gear and that won't turn the pump gear properly.
I'll post a picture of what the pump gear and slot in the torque converter look like.


----------



## Bob Young (May 27, 2018)

On the converter you can see the slots I'm talking about. On the left side of the schematic is a picture of the gear in the pump, those two tabs fit in the slot of the converter. This is just a wild guess but might give it a try. un-bolt the converter and see if it slides back about 1/2 Inch. If it doesn't then you will need to loosen the bell housing bolts and slide the tranny back to rotate the converter till it falls into the gear and then slides back. When it's properly set the converter will rotate freely to align with the bolt holes. then it can move forward against the flex plate. Good luck.


----------



## Charlie Ashby (Aug 23, 2018)

Tried and no such luck. 

Not sure why but 2nd gear just slips bad. now when i get if throttle off the line it slips going into 2nd.

The only thing that works is while in 3rd, if i floor it, the kick down activates and 2nd gear works perfect.


----------



## dd68gto (Nov 14, 2012)

Charlie Ashby said:


> Tried and no such luck.
> 
> Not sure why but 2nd gear just slips bad. now when i get if throttle off the line it slips going into 2nd.
> 
> The only thing that works is while in 3rd, if i floor it, the kick down activates and 2nd gear works perfect.


As mention earlier have you checked what you getting far s vacuum? Try unplugging line and see how it acts. It crazyehst a leak in that vscumn line will do to your shifts . I'm betting that's your problem , Doug


----------



## Charlie Ashby (Aug 23, 2018)

Yes, test vacuum at the line down by the module. it was 19. Also module is brand new.

new module
New vacuum line going down to the module
New filter
new oil
checked governor gear and its good.


----------



## Charlie Ashby (Aug 23, 2018)

Well, i pulled the trans last night. Gonna do a rebuild. 

Anyone have good experience with the B&M rebuild kit?


----------



## BearGFR (Aug 25, 2008)

Charlie Ashby said:


> Once I bolt it to the flex plate, wont it come right back forward again?


Yes it will. The purpose of pushing it back is to check the clearance between the converter and the flex plate, with the converter fully seated in the trans. That measurement tells you exactly how far the converter has to move forward when it's bolted to the flex plate. There's a range that you have to hit in order for it to be right. Too shallow and it will be putting constant pressure on the pump and will likely cause the pump to fail quickly. Too far and you run the risk of moving the converter so far forward that it disengages from the pump drive, or is such a weak connection that there's a risk of shearing something (like when you put a heavy load on a bolt that only has one thread engaged).

Bear


----------



## Charlie Ashby (Aug 23, 2018)

Well, rebuilt the trans. Went with a B&M Transpack.

Car doesn't slip when in drive and shifts perfect now. However if I shift into 2nd gear on my own, it still acts as if it is in neutral. If i give it gas, it will go but when I left off the throttle, it seems to go in a neutral state.

Super confused on what it could be.


----------



## BearGFR (Aug 25, 2008)

Charlie Ashby said:


> Well, rebuilt the trans. Went with a B&M Transpack.
> 
> Car doesn't slip when in drive and shifts perfect now. However if I shift into 2nd gear on my own, it still acts as if it is in neutral. If i give it gas, it will go but when I left off the throttle, it seems to go in a neutral state.
> 
> Super confused on what it could be.



Question: When you're cruising along in Drive, say 40-50 mph, and then manually downshift into 2nd _without applying throttle_ - what happens? Can you feel it downshift and start to get some engine braking effect, or does it feel like it went into neutral and started coasting?

Bear


----------



## BearGFR (Aug 25, 2008)

Charlie Ashby said:


> Well, rebuilt the trans. Went with a B&M Transpack.
> 
> Car doesn't slip when in drive and shifts perfect now. However if I shift into 2nd gear on my own, it still acts as if it is in neutral. If i give it gas, it will go but when I left off the throttle, it seems to go in a neutral state.
> 
> Super confused on what it could be.



Question: When you're cruising along in Drive and in high gear, say 35-40 mph, and then manually downshift into 2nd _without applying throttle_ - what happens? Can you feel it downshift and start to get some engine braking effect, or does it feel like it went into neutral and started coasting?

Bear


----------



## Charlie Ashby (Aug 23, 2018)

BearGFR said:


> Question: When you're cruising along in Drive and in high gear, say 35-40 mph, and then manually downshift into 2nd _without applying throttle_ - what happens? Can you feel it downshift and start to get some engine braking effect, or does it feel like it went into neutral and started coasting?
> 
> Bear


It feels like the car just coasts and does not engine brake. But if I give it throttle it will start going.


----------



## BearGFR (Aug 25, 2008)

Ah, ok then. Here's what Ron Sessions says about that symptom in his book: _How to Work With and Modify the Turbo-Hydramatic 400 Transmission_

"No Engine braking in S or L2 (manual second)"

"Faulty front (intermediate) servo and 2-3 accumulator assembly. Remove pan and valve body. Check for worn or damaged servo or accumulator oil seal rings, or damaged bore. Also check for stuck servo piston."

and/or

"Front (intermediate) band malfunction. Remove pan and valve body. Check for broken or burned front band. If damaged, check for disengaged anchor pin or servo pin"


Found on page 82 of my copy of this book:
https://www.amazon.com/Modify-Hydra...1537982900&sr=8-1&keywords=ron+sessions+th400

Bear


----------



## Charlie Ashby (Aug 23, 2018)

Well, i will give it a go. I replaced the 1-2 shift valve while I was in there as well as the seals. Also, per the kit removed the 2-3 accumulator spring.


I have some extra seals so I will pop it open and check it out.


----------

