TH400 acting strange

[PatJ]

I rebuilt a junkyard TH400. I used the Hughes 2288k kit with all the good stuff. No shift kit just stock setup. The build seemed to go well but now I am having some issues.

First off, I can hear gear noise in first and second. It is kind of a whine. Not loud but is noticeable. It is loudest in first, quieter in second, and gone in 3. I looked closely at the gears and torringtons when I was in there and all looked great. Searching on the net it seems like some TH400 do that and some don't and it doesn't necessarily mean anything is wrong. I still wonder about it because this is the first 400 I have had that did that. Thoughts?

The second issue is the big one. On the first test drive got about 15 miles out and the trans started to act like the kickdown solenoid was energized. Held gears way too long and was way too anxious to downshift on decel. Nursed it home. I thought the kickdown solenoid had stuck open with a chunk of debris or something so I cycled it several times and installed a temporary toggle to energize it. Once it had cooled it seemed normal. Hit the highway again and about 15 miles same thing. Temps in the pan are about 210 which was always normal for this motorhome on the freeway in the summer. I have B&M's largest stacked plate cooler in series with the stock cooler. Fill level is spot on and not foamy. While it was acting up flipping my kickdown toggle had no effect. Pull off and let it rest for a few minutes (not necessarily cool any) and it would be fine for a few more minutes.

Any thoughts on this? I don't know if the noise and the kicking down are related. Other than those issues trans seems normal. I already have another kick down solenoid on the way but since it seems to only happen once up to temp I don't know if that is really the issue. Thoughts? Anyone?

[PatJ]

Checked a few more things today. First flow to cooler. Disconnected return to trans and idles engine. Got a quart in about 8-10 seconds. Good flow to and through cooler.

Next checked pressures at idle. First "cold" (about 100 on Autometer gauge in pan.)
Modulator connected:
P 90
R 140
N 90
D 90
2 170
1 170

Modulator disconnected:
P 160
R 230
N 160
D 155
2 170
1 170

Trans warmed up until 150 indicated in pan. This time I used my toggle to energize the kickdown solenoid. These were with modulator connected.

Kickdown not on:
P 80
R 115
N 80
D 90
2 120
1 155

Kickdown solenoid energized:
P 80
R 100
N 80
D 105
2 120
1 135

Surprised to see pressure lower with kickdown solenoid open.

Pressures seem a little high to me but not a lot and also relationships between the gears seems alright. Might be my gauge is off a little too. I must have screwed something up because it isn't acting right. Anyone have any thoughts on this?

[KWTMECH]

Check voltage to the solenoid, should be zero until you engage the switch at the gas pedal. Also pull the governor out of the side of the case and take a good look at the nylon teeth and make sure the valve inside of the governor is moving up and down when you flex the weights back and forth.

Vacuum modulator hooked up correctly at the engine?, constant maifold vacuum, no leaks

[PatJ]

Governor looked great at rebuild as well as gear on the output shaft. The wiring on the solenoid is also functioning correctly but I haven't ruled out something wrong with the solenoid itself so I have a new one on the way. The solenoid is one I had on hand because the one in the JY trans had a cracked wire. I am hoping for that to be the issue now because it is easy to fix. It is a pretty simple part though so who knows.

The vacuum to the modulator I hadn't really thought of because the old trans acted fine up until it grenaded. That is a good point though. I have strong vac to the modulator at idle but haven't really traced the line and being this is a CA emissions 1984 that line may go through some emissions BS that does who knows what. So I will look in to that too.

Getting ready to hit the road with the pressure gauge hooked up. Gonna try to get it to fail with the gauge on it to see what is happening.

[PatJ]

Drove around town and pressures seemed fine to me . 25 MPH in D (3) is 90 at idle and 120 if I gas it. Once fully warmed up coasting is about 70 and up to about 110 if I hit the gas. Forced in to 1 or 2 it is around 165 spiking to 180 which seems a touch high for a stock rebuild but not outrageous at all.

Driving around town for 20 minutes or so I got temp up to 210F in the pan and seems like it is still climbing? Don't really remember what it was in town before the rebuild but doesn't 210 seem high for 35 MPH? What could I have messed up to make it run hotter than before?

[Backncardr]

With regard to the gear noise-they used straight cut gears in the motor homes ala TH475. Noisy but stronger. As to the cooler yer using is it connected in series with the factory cooler located in the radiator? You would want to plumb it in after the the oil exits the factory cooler. I prefer to eliminate the factory cooler altogether they are a source of restriction particularly after a trans grenades-they are made of a bronze like mesh similar to the factory fuel filters in the old Quadrajets. You have an excellent cooler with the B&M.

[BurnBlue]

Is the cooler mounted vertically or horizontally? If mounted vertically the air will trap in the cooler and will not cool properly.

[PatJ]

The junkyard trans I rebuilt and installed is out of a 1979 GMC 3500 van with 106k miles on it per the junkyard. I even got the VIN. I figured if I am gonna spend the cash on a junkyard trans I might as well get the bolt on yoke output like what was there and that is what they had. So sadly no TH475. Actually the motorhome's original TH400 that I removed wasn't a 475 either and I was expecting it to be.

The B&M cooler is connected in series with the factory cooler and after the factory cooler. But BurnBlue is right, it is mounted with the fittings down. I downloaded the manual yesterday and noticed where it said not to do that. Next thing on my list is to clock the cooler differently and hope that was it!

Thanks for the help so far!