Tranny won't shift into third!

[porkchop]

After all the work I have done and the time that I have been without my wag, more troubles. It will not shift into third gear. It was rebuilt when the new rear output shaft went on. If the little check balls are in the wrong place can this cause the problem? I am at a loss here. I am working with the one who rebuilt it to try to figure it out, but I thought I would throw it out to you all to get some fresh Ideas. Thanks. I miss my Wag. :( :( :( :( :(

[Snakeyes_Tx]

Band out of adjustment perhaps? Vaccum modulator out of adjustment?

[Shake N Bake]

Vacuum modulator is the first place to check, I usually just run a vac line down to the tranny (temporarily) I've kinked that hard line more times than I can count. Once I do it, truck refuses to shift into 3rd.

At the same time the shift from first to second are noticeably harsher.

Andy

[porkchop]

Were can I get a new modulator? The one I picked up does not fit, with or without the elbow. They said it was for a jeep wag but we all know how that goes :rolleyes:. Will a bad modulator cause it not to shift even when you manually shift it? I just have the vac line going to the tranny, no hard lines. I am going to pull it again but before I do I want to try and figure out if it is something I can fix before I go through the trouble. Thanks guys.

[BIGYELLOW78J10]

I'm pretty sure the modulator is the only thing that controls upshifts. What parts place gave you the modulator? I am chasing an oil pressure sender. Their computers say it works, but their parts don't fit my 360. Good Luck

Daniel

[Kenall]

ok..it wont perform a 2-3 shift...right??

well whats the quality of the 1-2 shift, harsh on full throt, nice on part throt, or snappy no matter how much u got ur foot into it???

the modualtor is the predessesor of the throt postion sensor. the govenor, (the device behind the 4bolt plate behind the ID plate on the P side), is the equivilent of a speed sensor.

the modulator will control the delay and quality of shifts. light throt, faster soft shifts. heavy throt, longer snappy shifts. but wont prevent a shift from occuring.

the govenor controls up and down shifts depending on rpm. a failed unit can prevent any shift from occurring, prevent 2-3 shift or prevent the tranny from beginning in 1 from a standing start.

the modulator deals with shift quality, but the govenor deals with weather or not a shift takes place.

BM makes modulators for the th400. ask any parts place that sells BM stuff. small and gold in color and fully adjustable to taylor shift points for when u change RP gears.

get the Ron Sessions Motorbooks International
Th400 book.ISBN# 0-87938-267-8

[Snakeyes_Tx]

Oh yeah.. forgot about that governor thing.. but generally when the governor breaks, it doesn't come even out of first. I snap the little plastic gear in TH350's governors all the time...

You guys don't even have kickdowns like us 727'd people.. so I still suspect the modulator.

[porkchop]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Kenall:
ok..it wont perform a 2-3 shift...right??

well whats the quality of the 1-2 shift, harsh on full throt, nice on part throt, <HR></BLOCKQUOTE>

This is the problem. And that is how it shifts. I did pull the goverenor and look at it and the valve was moving fine and the gear was not broken. I am going to go and look for that BM part tonight. Thanks.

[D.A. Davis]

Ok, here's how it works. If the transmission
is shifting fine from 1st to 2nd, then it's very probably not the modulator valve or the vacumm supply. By alright I mean the shift point is in the prefered speed range, and feel. The same with the governor, except it only deals with speed. Yes, it will effect the shifting if you omit or misplace a check ball in the valve body. Make sure you don't have a sticking shift valve in the valve body. Also, did you pressure check your direct clutch pack, before you completed the transmission assembly. You can do this now with the valve body removed. I can't off the top of my head remember which port (hole) supply's the direct clutches. You can air check all you clutches and the band. If I remember right, the band is only adjustable by changing the servo pin. GM offered several pin lengths, depending on the application. But, I've never had to change one on any of the 400's I built. Maybe this helps.

[porkchop]

We did a pressure check before we were done and it worked great.

[woodybeone]

I had a similar problem on one of my GW's. It would hold gears for a long period of time between shifts and sometimes it would not shift into 3'rd at all. My problem was a weak spring and sticky movement on the lever at the side/rear of the carb (part of the linkage). I replaced the spring , lubed the hinge point and it solved the problem. Hopefully your solution is that simple !

[porkchop]

I hope it is that simple too. So far it is looking like it is going to have to get pulled again :( I am trying to avoid this at all cost. I don't have the time or money to do it again.

[BIGYELLOW78J10]

Hey pc,

Have you checked the shifter linkage? We have a van at work that only drops into third when the gear indicator is on the right side of neutral. What if in the hookup, the shifter got out of whack? I bet you've tried it, but this is the simple fix I'm crossing my fingers on. One more thing, back to the modulator, what if it was A. Broken or B. adjusted way out of whack? Couldn't it delay the shift so far as to make it seem to not happen? If I were driving and the tranny wouldn't shift, I don't think I'd rev up and go til it did. Can the modulator delay work like that? Good Luck PorkChop!!!

Daniel

[jeepbob]

I had the same problem when I put my tranny back in and it was because I had put a hole in the vac tube going to the modulator. I repaired the tube and that fixed the problem. When you put the modulator back in you did remember the pin right? Also check to see if you have power going to the kick down solinoid on the drivers side of the tranny, if you do then your kick down switch is shorted out or you hooked up the wrong wire to the tranny. With power to the solinoid, you will see very late, high rpm shifts. Either the lack or vac or power to the solinoid will override a manual shift going from 2nd to 3rd.

[Lindel]

I might be a little late to the game, but if the modulator is bad, or the hose to it has a leak, here's what will happen. It won't shift into 2nd until the engine is screaming at VERY high rpm's, and the same for third.

The reason for this, is the tranny gets it's upshift impulses from the vacuum modulator. If there's no vacuum (sans leak from bad hose, or ruptured diaphram), then the tranny "thinks" the car is at maximum acceleration, and WILL NOT shift until the gov tops out. The shift will be extremely hard, and starts the cycle over again on the 2 - 3 shift.

If the modulator is bad, in your case, it might not shift into 3rd until you're close to 80, or so.

[porkchop]

Ok, when I take out the modulator it has plenty of vacuum. It holds the vacuum when I use my pump, and the hose is good. Will it shift into second easy when going really slow and hard when stepping on it with a bad modulator?

[Kenall]

did u remove the modulator diaphram (MD) from the case and test to see if the internal plunger moves with the vacum?

on a limb here but...is the modulator valve (MV) IN the case...is it free to move.

is the detent switch/wiring faulty. if it is, it will tell the tranny to hold second gear for a long time. as if u mashed the throt passing some slo moving wrangler. ;)

u have the large MD body on the right-angle jeep adaptor? if u buy the BM replacement MD that is much smaller than the OE type. the replacement bolts direct to the case body w/o the angle adaptor. as a result, urll also have to obtain a normal th400 MV from the local shop as the OE valve is of a different length.

[Lindel]

If the modulator is bad, it won't shift easy at all. It'll "think" you want to go as fast as possible, and will shift accordingly.