M1009 TH400 Acting like a High Stall converter after rebuild.

[Wetbehindears]

Hey Everyone,

So my sons M1009 had a VERY weak reverse, barely enough to back up our driveway (not very steep grade). So we bought a rebuild in a box kit from www.bulkpart.com for the TH400. When we tore down the transmission, there was really never any big indicator of a failed part inside. We replaced all the clutch packs, and resealed all three drums, new band, etc.... Unfortunately I was at work when he put the valve body and lower end stuff back in.
Soooo....
Got it all button back up and the truck now acts like it has a high stall converter in it.
Both reverse and forward grears will not engage until you rev the truck way up?
So, Im fishing for knowledge.
Anyone out there got any ideas?
Is there a chance he installed a part from the kit that was meant for a gasser and not a diesel?

 

[DriverSideImpact1008]

Check the trans fluid level and check all the vacuum lines. Both of those are the simplest things that could cause it to act weird.

 

[phil2968]

Low pump pressure. Put a gauge on it. From the TM9-2320-34, page 5-52.....
"Remove pressure tap plug (3)
located on left side of transmission
between downshift switch connector
(2) and manual linkage....."

Get a gauge on it, 200 psi. It should read like this.....

A., Brakes applied; “N” (Neutral); engine
at 1000 rpm,-------------------------------------55-70 psi
B. Engine at idle---------------------------------60-85 psi
C. Brakes applied; “ D“ (Drive); engine at
1000 rpm.----------------------------------------60-90 psi
D. Brakes applied; “1” or “2”; engine at
1000 rpm.----------------------------------------135-160 psi
E. Brakes applied; “R“ (Reverse);
engine at 1000 rpm.---------------------------95-150 psi
NOTE
Downshift switch is located on
right side of accelerator pedal
plate,
F. Brakes applied; “D“ (Drive); engine at
1000 rpm; downshift switch activated
by pulling out.----------------------------------90-110 psi
G. Governor check; vacuum line
disconnected at modulato; "D"
(Drive); brakes released: check
pressure at 1000 rpm. Slowly increase
to 3000 rpm.-----------------------------------Pressure drop of 10 psi (69 kPa) or more indicates a problem.

 

[wayne pick]

The one component not included in the rebuild kit is the pump and it is more than likely the problem.

 

[Wetbehindears]

Ok, we finally got around to trouble shooting this. For awhile, this truck would start to go into gear at higher rpms, now even reving up, it wont engage. Checked pressure and have 0 PSI no matter if in park, gear, etc. Just dropped the pan to check the pickup tube and it all looks good.

Question= Ive heard you can drop the filter off and check if there is suction on the pickup tube? Is that correct? Because we just tried it and there is NO Suction at all on the pickup tube. Pump?

 

[Wetbehindears]

And we are back again.
Ordered a new trans pump and it came in yesterday. So we put the pump in, installed the trans, got the fluid level as best we could cold, fired her up, and BAM... It worked!! Went right in to all the gears. We let her warm up and topped off the fluid until it read perfectly on the stick. My son took off down the street, it shifted good (a little late) but went through all the gears. Then he wanted to get it out on a 55mph road. When he took off, it never came out of 1rst, and now it wont go in reverse? Im dead set on getting this fixed, im afraid he is starting to get discouraged!! Any ideas?

 

[cliffyp]

A lot of times, not getting out of first is the governor. That's quick and easy to check. You may have some debris from your build that is now blocking a passage causing both loss of reverse and 1st only. Put your pressure gauge back on and see if your pressure either too high or low, could be a stuck valve in the pump or debris. Other than that, maybe the rear servo assembly.

 

[Wetbehindears]

Ok, im heading out to take another pressure reading and see what we have now. Im determined to get this figured out! Here is a quick ESPN breakdown of the history of all this, maybe is will spark some ideas from some of you more advance transmission guys.
1. Bought M1009, transfer case, and transmission had been removed and sitting in the back.
2. Towed it home and decided to bolt everything up and see what was going on.
3. Torque converter sounded like a baby rattle. Order new Torque Converter and new Flex Plate.
4. Dropped transmission, installed new Torque Converter and Flexplate, and she moved.
5. Reverse started getting weak (about 1 month after new converter), to the point we could not back up the driveway, decided it was time for a rebuild. Ordered two books and full rebuild kit from www.bulkpart.com.
6. Pulled all apart, all new seals, bushings, clutch packs, etc... pulled every drum apart and resealed via book instructions. Re-installed transmission.
7. After installation, she acted like it had a high stall converter. Would only go into forward or reverse gears at high RPMs. Did a pressure check, but could get nothing? So, ordered a brand new HUGHES transmission pump.
8. Dropped the transmission again, and installed the new Hughes pump last night.
9. Started her up cold, and she engaged into all the gears. Drove around the neighborhood and she went into all the gears and was shifting like normal (only 1 and 2nd as our neighborhood is 20 mph. After driving around for awhile, starts slipping in reverse!
10. Wake up this morning, start her up, she goes into all gears just fine. I back up and down the driveway and she feels fine. Turn her off, come back 30 mins later, and she wont engage into reverse? Goes into 1,2,3, but I cant get out of the driveway to go and drive her and she what all shes doing!

 

[Wetbehindears]

Ok, the results are in:
Neutral= Idle: 110psi
Drive= Idle: 75psi 1000 rpm: 80psi
1rst= Idle: 80psi 1000 rpm: 110psi
2nd= Idle: 65psi 1000 rpm: 80psi
Reverse= Idle:10psi 1000 rpm: 10psi

 

[cliffyp]

I'm going with stuck valve or blocked passage, obviously reverse line pressure is way low.

 

[Wetbehindears]

Ok, ive dropped the pan off and removed the valve body (trans still in truck BTW). I was at work when my son installed the valve body and so far...the only thing I have found is a crack in the accumulator housing. Obviously thats not supposed to be cracked, but I have some quick research to do to find out what that part actually does.
IF ANYBODY can explain how to fully air check the clutch packs while im in this deep, please feel free. I have bits and pieces of info on this, but not a write-up per say. Ohh, and I will update shorty with pics of my cracked accumulator housing.

 

[Wetbehindears]

When Air Checking. If I blow air into #2, I can hear a clunk and very tight air seal (120psi). If I blow air into #1 I can hear the clunk, but lots of air coming out of #3. My rubber tip is too large to get down into #3 to try to blow air. Is there anywhere else I can air check, and what are your opinions of these results so far?

 

[cliffyp]

What you labeled #1 is the reverse passage, #3 is the direct clutch, I don't know if they should be flowing air together or not.
I'd look through all the components from the rear servo. That has both the 1-2 accumulator piston as well as the reverse servo piston in it. If it's outa whack, it can cause loss of reverse and 1-2 up shift. Check the seals to the pistons, make sure they aren't damaged. Check the pistons themselves, the cover, the gasket for the cover. If you're getting an internal leak through any of these that would explain the low pressure in reverse. I'm thinking the rear servo is where your problem lies.

 

[Wetbehindears]

Thanks Cliffyp, and I do agree with everything you said. Looking in the manual it does say that there will be a moderate amount of air between the 1 & 3 Passages, i just dont know how much is moderate. I was looking last night and it looks like I could install the rear servo and pressure test it. I see the port that goes from the valve body into the rear servo, so I think I will try that today and see if I have a leak there.
Question= I pressure tested my accumulator housing (the cracked on that I now have on order) and it leaks like crazy. What I cant figure out is does the reverse line pressure go through this or not? Im replacing it regardless, I just cant figure out if that accumulator has anything to do with reverse?

 

[Wetbehindears]

Just to follow up.... all of our troubles came from a cracked accumulator housing on the bottom of the valve body. Technically this could have been repaired without even dropping the transmission. However, Im glad we got the job done!! 200 miles on repair and shes still going strong! Heres a pic. Just something to watch out for!