TH400 over-run

[BMFB]

Greetings!

I have a TH400 that was built last year. The builder has since died...

So far its been a great trans. Nothing major done, reverse manual valve body, steel front drum, 4 clutch direct pack, stuff like that. was supposed to handle up to 1200 hp

So this trans is sitting in an all steel vehical, with no padding and I can hear everything this things doing. from the first time this thing went in it made this noise in 1st and 2nd gear whenI would let off the throttle and coast. Describe it as a whirring noise...I was told t was an over-run clutch and that it was normal. Last night, it started doing the same thing in 3rd gear, and it never has before....problem?

 

[BMFB]

Re: TH400 over-run

Things I learned.

first and second gear have an over run so that when you are in decel in those gears they dont try to overspin the engine. Third gear does not have any way to do this.

Also; you should never hear the over-run clutches.

the only way this could happen is if the torque converter was beginning to fail, and you were hearing the bearings screaming in pain.

you should change automatic trans fluid after the first 500 miles.

Front axles out of 4x4 blazers make alot of noise when that are locked permanently in 4x4 mode, and 1 quart low, and have one tire at 15psi and the other at 40.

on a high note, I fixed my issues...trans is great...front axle seems cool but somewhat noisey. Fresh quart of 140w seems to have bought me some time.

 

[jamnut]

Re: TH400 over-run

I never coast with 350's or 400's that have manual valve bodies. It's better on the trans if you always try to get it into 3rd before letting off so it can coast better. I also never downshift when coming to a stop, just stop with the trans in 3rd and then get into low to take off.

 

[BMFB]

Re: TH400 over-run

I apprechiate this advice. It makes sense with the 3rd gear coast, because aparintly with my valve body all of the 'saftey' features of the trans have been removed.

 

[Windedv6]

Re: TH400 over-run

I had the same noise in a $4,000+ Coan Extreme Duty Trans filled with goodies. I was told the whine was normal in some trans. Whether the noise was the real problem or not this is how it ended up...

Anyone that doesn't run a shield should consider using one...It blocked parts from coming through the floor and probably saved a trip to the hospital...or worse...

Here is 10 lbs of shrapnel that ended up on the track verses inside the cab...

Nothing is bullet proof and things can go wrong. I was lucky that I was coming off of the trans brake at the line when it exploded. Had it been down track I would have probably bit the wall when all the oil and parts blew.

I put in a new Reid Super 400 case with all billet internals (although my previous had most of this stuff already.

This is a full lug case the is SFI approved without needing a shield. It makes the stock 400 seem fragile in comparison...

The sfi bell housings do not bolt on the pump bolts which is a nice plus and the bell housing are smaller dia (large enough for performance convertors) which makes putting in the trans/engine bolts a snap...

John

 

[BMFB]

Re: TH400 over-run

Nice!

Coming off the trans brake sounds right, I'm afraid of those things...I do mine off the brakes with a touch of antilag.

I spent 750 on this trans with the valve body and its been good so far. I confirmed that the sound was the front axle by disengauging it from the drive line and all of the noise went away. So far so good on the trans luckily.



This is me coming off the line. I spun all 4 of the ET drags, was dusty though...