Lock up in 4th gear

[03spoolindmax]

Just rebuilt my trans and it has approx 100 mi on it. Sometimes it'll lock up in 4th gear around 35 mph on light throttle. Will unlock when shifting to 5th then lock again when it's supposed to around 45 mph. Trans build consisted of altos for c1, raybestos for c2-c4 and I reused the c5 (they looked perfect when I tore it apart). I put a 6 speed drum in it also. Used the trans go converter valve with longer spring and no ball (same thing I did to my last trans I built and never had a problem) also replaced speed sensors, pressure manifold switch and internal harness. Trans shifts amazing and smoother than my first trans I built. I just get an occasional early lock up in 4th gear with no codes. It's also an 03 trans in an 05. Only code is for G solenoid. I'll be sending the TCM out shortly to have mark reflash it with an 01 software.

 

[THEFERMANATOR]

Don't know what to tell you other than mine does the same exact thing. I run an 01 OS in my TCM, and it has done it with 2 different TCM's and 3 different OS's. The 01 OS does it the most. I can pretty well count on mine to lockup in 4th at 35 if I'm running for more than a few miles at that speed. It defies all of the lockup tables, but still does it. And it unlocks when it shifts into 5th, and follows the lockup table in 5th. Also I have found it will unlock if I let off the throttle, but normally relock right away if I hold 30-35.

 

[03spoolindmax]

Almost the exact same thing that mine is doing. Seems to lock up in 4th when up to temp. It'll lock almost immediately as it shifts into forth. Then unlock for 5th and lock again at 45 when it's supposed to. It'll unlock when it's in 4th when I let off the throttle but will not lock back up again unless I go to 5th or slow back down and start from first again.

Besides that problem the trans shifts flawless. I've very happy with how this build came out just kind of puzzled on the 4th gear lock up.

 

[THEFERMANATOR]

Your not alone. I chalked mine up to my lowered shift points figuring that must be causing it. It never codes, but mine will often times relock when I get back on the thottle so long as it stays in 4th. Sometimes it will go weeks without doing it, then it will do it non stop for days.

 

[03spoolindmax]

I just wanted to make sure it won't cause any damage. Seeing it's just an early lock up I don't see how it could damage anything considering when in tow haul it locks in 2nd anyways.

I'm sure I could live with it if it's nothing major and won't cause damage. Glad to know I'm not the only person who has experienced it.

 

[Harbin_22]

Did all this start after both of you built the trans

 

[03spoolindmax]

Mine started about 25-30 miles into the rebuild. The last trans I had in it didn't do it. I did the same exact mod to the trans go valve as I did in my last one with the same spring. It's hit or miss sometimes it'll do it and sometime it won't an only in 4th gear.

 

[THEFERMANATOR]

Did all this start after both of you built the trans

Mine was in for over a year before it first did it., Sometimes it will go months without doing it, then it will lockup everytime I go into 4th so long as I'm driving it easy. No ryme or reason to it, but I can scan it and see the TCM command it to do it.

 

[03spoolindmax]

What I've noticed is if it locks up in 4th and I hit the unlock button on my BT box it'll immediately unlock. Which leads me to believe the TCM is commanding it to lock and not an internal problem.

 

[THEFERMANATOR]

Mine started doing it again yesterday hauling a small trailer. It will get your attention with a trailer behind you and it drops into lockup at 35 when your on the throttle. It's not doing it today though, go figure. I feel your pain, wish I could tell you why it does it. Guess it's a ghost in the machine as they would say.

 

[03spoolindmax]

Yeah mine comes and goes. I can go a few days without it happening. Then it'll do it for a day or so and go away.

I just hit the unlock button on the lockup box until I hit 45 or so it doesn't do it.

 

[Mike L.]

You guys might have a problem with the spring that you chose.

 

[PACougar]

Have you tried moving the lock up speeds in the tcm just to see what happens?

 

[03spoolindmax]

You guys might have a problem with the spring that you chose.

That was my main suspicion. I just don't get how it'll unlock when commanded. I thought the TCC solenoid was only energized when lock up was commanded threw the TCM.

 

[Mike L.]

Have you tried moving the lock up speeds in the tcm just to see what happens?

I don't think you can do much with that. There may be a problem with the spring moving around and coil binding in the pocket where the check ball was removed. A deep dished pocket is not the ideal seat for a spring.

 

[PACougar]

I don't think you can do much with that. There may be a problem with the spring moving around and coil binding in the pocket where the check ball was removed. A deep dished pocket is not the ideal seat for a spring.

Well that would certainly make sense seeing how it happens randomly to them. I know the 01 OS is different than the newer OS's, I don't even know if it can be changed?

 

[03spoolindmax]

I don't think you can do much with that. There may be a problem with the spring moving around and coil binding in the pocket where the check ball was removed. A deep dished pocket is not the ideal seat for a spring.

What bugs me is I wanted to use my stock valve assembly and grind the flat on it. but since it had the bleed hole on the side I was told it needed to be welded shut or it wouldn't work correctly. I didn't have access to a welder at the time of the build.

 

[Mike L.]

What bugs me is I wanted to use my stock valve assembly and grind the flat on it. but since it had the bleed hole on the side I was told it needed to be welded shut or it wouldn't work correctly. I didn't have access to a welder at the time of the build.

What dumbshit told you that?

 

[03spoolindmax]

What dumbshit told you that?

I'd rather not get Into that :rofl:

So with an 03 trans I can just grind the flat on the stock valve like I originally wanted too and toss the trans go?

 

[THEFERMANATOR]

I'm running a TRANSGO valve with the white spring in mine. No valve modifications to run more pressure other than the valve swap and the 170 spring. Also I'm running stock line pressure with no shim. Mine gets commanded to lockup when it does it. Can watch it on the V2 BBL when it does it. it is completely random, but seems to do it most when I run at 30-35 for extended periods with a trailer in tow in reguar mode. I only turn tow haul on when I'm running my tow tune for bigger trailers. I always figured it was a ghost from my swap.