Strange shifting problem

[zeus87gn]

Hello Everyone,

A little while back, I serviced the trani in the 87. Sounded like a good service thing to do because it hadn't been done in about 5 years and was shifting kind of sluggishly. While I was in there, I also changed the Lockup solenoid and the 4th gear switch. Shifting is quite crisp now that I have the TV cable adjusted acceptably. I can tell the lockup converter is now operating.

Here is the problem...since having done this, the 3rd to 4th shift will cause an almost violent back and forth shutter (for lack of a better word) in the entire vehicle when the converter locks in 3rd gear. If the converter does not lock in 3rd, the 3rd to 4th shift is normal.

After doing some reading, I have found out that the BRF version trani also has a 3rd gear switch. Should I replace this as well? Or am I missing something else altogether? :confused:

I am not fully versed on A/T, but I'm not afraid to learn what I need to.
Any help would be greatly appreciated.

Thanks,
Patrick

[zeus87gn]

Is anybody willing to help me tackle this, or is everybody as doumbfounded as me?

I am at a loss here with this, so any input at all would be appreciated.

Thanks,
Patrick

[kenmosher]

Did you get the O ring out of the valve body before the new filter went in (I know, probably overly simple, but sometimes it's that stuff that trips us all up!)

The shudder/stutter leads me to think the new solenoid might be sticking or "chattering" for some reason.

Sounds like it is locking/unlocking rapidly on the shift for some reason ... maybe:

Leak around the soleniod itself in the valve body
Leak around the VB gear switches

[zeus87gn]

Ken,

Thanks for the reply.
Yes, I got the old o-ring out. Wasn't very diffucult.

When you say chatter, it makes me think of a clutch. Maybe I should describe it differently because this is not the same feel. (my utility vehicle has a clutch). Inagine trying to push the car forward in park...the trani won't let it move but a bit...you can feel the entire weight of the body rock back and forth against the lock in the trani...same type of thing, only I'm going down the road when this happens! Strange? Yes! I have never encountered anything like this.

I would think the valve body gasked would be easy to replace, but I have never done it. I guess I can find some info in the tech pages?

Any other insight?

I appreciate your help,
Patrick

[kenmosher]

It almost sounds like the band is hanging up ... but that doesn't really make sense, since it is used on the 1->2 shift and then it hands over from band to clutches in the 2->3 shift.

Only other thing is the lockup solenoid (which is suspect, since it was changed) that could be locking/unlocking the converter clutch .

Otherwise, it's something deeper in the VB.

Here's a bunch of trans info:

http://www.gnttype.org/techarea/transmission/transpage.html

[zeus87gn]

Thanks again for the help.

The inner workings of automatics are still beyond me. I will do some reading up on them for better understanding.
For the time being, is there a way to 'hot wire' the lockup solenoid? Just flip a switch when I want to allow it to lockup without causing trouble? If I can keep it from locking in 3rd, this problem doesn't occur.
I hope to get to changing the 3rd gear switch this weekend. Do you think this will help?

Patrick

[Keller]

You can connect pins A and F on your ALDL with a switch to manually control lockup. However, leaving the switch open will not defeat lockup. (i.e. The trans can still lock up when it wishes.)

[zeus87gn]

Ok,
I read on installing the switches for TCC lockup, and (if I understand) I think the 'TCC defeat' is really what I am wanting to do. I would still like the converter to lockup, just not in 3rd gear only in 4th (like at highway speeds).

Another concern has crossed my mind on this problem. Can this problem I am experiencing be caused by thrust bearing wear? I noticed some in line crank play when I changed the timing chain back in Nov 2000. Probably enough to just barley stick the tip of a very small flat tip screwdriver into.

Or possibly rear end gear slop?

Our GN has just over 190K miles on it. If I calculated correctly.

Thanks again for the help,
Patrick

[Keller]

The only way to get the trans to not TCC lock in 3rd would be to disconnect the 3rd gear switch input to the ECM. Pretty sure that would take 3rd out of the picture.

You could remove the TCC ECM output (contact closure, really) to the trans. The latter would definitely make things an all manual TCC affair. Another route would be to modify the chip code to not do TCC activity and make the TCC entirely manual. You'd have to wire directly to the trans, as the ALDL would not do it anymore.

The amount of play you are talking about is negligable, I believe. Consider the slop in the converter and such that goes into the equation. This hardly all can transmit such minute motions to the trans. And it all tightens up when there is oil pressure in the bearings. Motion in the rear end fore/aft is lost in the driveshaft yoke. You would have an awfully worn gearset in the rear end to get as much slop as you are worried about.

[zeus87gn]

Thanks for the quench on my worries. I would hate to get into rebuilding the motor for something as crazy as this. It has run too good too long.

Ken mentioned something about the bands. I have heard that they are adjustable? It would be worth my efforts if it wern't to diffucult. Is there something (book, manual, etc.) available I can download or buy that can explain this to me? I really want to get to the bottom of this.

I do appreciate your time.

Patrick

[kenmosher]

Bands on the older THM350s/400s are adjustable, but there isn't any adjustment on the 200-4R.

[bragggf]

This almost sounds like what it feels when you have a problem with the TCC solenoid or TCC itself and it starts locking up at very low RPM (i.e. 2nd gear, etc..). To eliminate the TCC as the source of the problem you can either unplug and test it or lightly touch the break pedal before the shift into OD. I Believe there is also a checkball in the input shaft going into the converter that some folks remove to get a more positive TCC engagement.

Is this issue only at part-throttle or WOT? If it has been built properly it can handle a shift into OD at WOT. If it is a stock trans build don't bother trying OD @WOT as you will eventually break it.

-Gerry Bragg

[zeus87gn]

Well, I looked into this problem over the weekend, and I think I solved it. Now I just have to get the alternator fixed and I will know more the more I drive it.

Anyway, I changed the third gear switch to see what would happen (I already had purchased it anyway), took it for a spin and it did help. The 4th gear 'slam' was almost eliminated with this. Cut the rocking sensation to next to nothing.

However, I did something else, I changed out the stock chip for 'Chuchy's' chip. Up until sunday evening (when the Alt quit) it was running like a champ. No lockup in 3rd, no slam into 4th, then lockup in 4th. Smoooooth shifting, just what I was looking for. In addition, the GN now has more power, no more audible spark knock, seems to have quicker spooling, better idle. All around vastly improved operation.

Chucky, I don't know who you are, or where you got your programming knowledge from, but thank you. :hail: Kimberly says her GN has never run better since I met her.

Thanks for all the other input as well.

Patrick