1-2 shifts early

[68Camaro]

I have been working out the bugs of installing a CZF trans in a 68 Camaro (stock 327). I did a stock rebuild and added Bruce's shift kit and servo and it is working very well with one exception, the 1-2 shift under full throttle is shifting very early, around 3500 rpms. The 2-3 shift is at 5000 and if I allow the trans to shift into 2nd, then go full throttle, it will downshift to first and run up to 5000. I can manually hold first gear.

I have changed out a few parts trying to figure this one out, put the old servo back in, check the govener and replaced the spring on the heavy weight, changed springs in the 1-2 accumulator, removed one shim from the adjustable servo pin. Each minor change did make slight differences in the shift quality and timing, but nothing changed the full throttle 1-2 upshift at 3500.

I am now thinking valve body, but can anyone offer up some ideas on what might be happening?

Thanks,
Greg

 

[MeanBuicks]

Try removing the governor spring from the heavy weight altogether. Don't chase your tail by making changes to the servo, servo pins, accumulator etc. Those items only come into play after the 1-2 shift valve has stroked so they are downstream from your problem.

 

[68Camaro]

Greg,

Thanks for the reply and narrowing my search for the problem. My explaination wasn't as clear as it should have been, I have tried the govener both with and without the spring on the heavy weight, no difference on the 1-2 full throttle up shift. I actually like the weight in the govener bringing the part throttle shift points down.

How does the govener signal the 1-2 upshift at full throttle and how is it different from signaling the 2-3 upshift as this one occurs at 5000rpms? This is a strange problem, any other ideas?

 

[Russ Merritt]

I have the same EXACT problem! Shifts at 3500 1-2, and 5200-5300 2-3. WTF$#%..... over!

 

[WE4]

Hrmmmmm What rear gear is in the 68 maro? I am curious. As for Russ's problem, all I can say is what it is not and it is not the kit. Tv cable all ok? if it will downshift and run up all else (gov and such) is working too. What is mainline pressure in this trans?

Bruce
WE4

 

[68Camaro]

Bruce, thanks for jumping in to help out. I have a 3.42 posi out back with the correct gear on the govener. Any ideas on where I can go next?

Thanks,
Greg

 

[68Camaro]

Bruce or anyone else,

Any ideas on what may be causing this problem? How does the govener signal the 1-2 shift and the 2-3 shift, what is different?

Thanks,
Greg

 

[HOTTOGO]

My limited knowlege tells me the gov works the same on all shifts, the faster it spins the tighter the balls seat the less the bleed to the point line pressure overcomes shift valve spring pressure, be it 1-2, 2-3 or 3-4 so I would say one of the determining factors is spring press.

 

[68Camaro]

Mark,

Thanks for the reply, so maybe I should look and the 1-2 valve set up in the valve body? From the ATSG manual, I see only one spring in the 1-2 valve setup, 335 = spring, 1-2 throttle valve. If this spring was damaged or weakened, would that decrease the spring strength and lower the shift point?

Or could the valve (331 in the manual) be sticking close to the open point and shifting early, I dont' see a spring in the manual for this valve.

Thanks again for your help.
Greg

 

[HOTTOGO]

What vb mods if any have been done?

 

[68Camaro]

I used the simplest Superior shift correction kit and Bruce had me change a couple of other items as well when I added his servo. I am resonably confident that nothing was changed in the 1-2 valve area.

I also used Bruce's separator plate, it has one hole blocked off. Let me know if you have any ideas.

Thanks,
Greg

 

[HOTTOGO]

My last idea would be the TV modulator upshift spring (ATSG # 315) without going into complicated detail of what it does, for lack of wanting to type that much. It takes tv pressure at a certain point (pressure) and uses it to help the 1-2 shift valve spring or any for that matter, hold the valve closed against gov. pressure to dely the upshift. I think maybe your tv pressure is not high enough at the 1-2 shift to overcome tv mod spring pressure. And it does have enough to do it after detent down shift and that is why it shifts at 5000 after that. Some models don't even use this spring, my czf does have it and all my shifts are at the same rpm, but yours may may differ 'cuz of your mods and pressures, try removing this spring and see what happens.

Or try raising tv pressure controlled by tv limit valve or line pressure. Whats your pressures?

 

[68Camaro]

Mark,

Thanks again for your thoughts, this sounds like possible solution. If I were to remove the spring, would that have an effect on the shift points, raise or lower them?

I haven't checked pressures in a while, but the last time I did they were: Park: 75 min TV, 225 full TV, Rev: 125, 225, Drive: 75, 225 and 1-2: 125, 125.

I will probably pull the pan again this weekend and try your suggestion, if you have any other ideas after seeing my pressures readings, let me know.

Thanks,
Greg

 

[77 cruiser]

Dosen`t look like you`re getting the boost press. you should be in 1st & 2nd. I don`t know if that would make a diff. on your prob. but it would be bad for a manual 1-2.

Jim

 

[HOTTOGO]

The modulator valve purpose is to dely (raise) shift points at more throttle opening, but not past what gov. is set at, that's why I think it might help raise the 1-2 shifts up to what the rest are. Two other suggestions while you are in there; 1.) check the modulator vave and 1-2 shift valve train for "ANY" possible sticking and if they are questionable lap them to losen them or what ever it takes to get them moving freely were they will slide in and out just by tilting the vb side to side. 2.) is because of your pressures if that's still what they are, they need some help. If you have 75 in park and neutral you should have 150 in rev. and 1-2 at min. and you 1-2 max is non exsistent. That maybe part of the prob. not getting the TV pressure required for modulator valve movement at 1-2. Removing the modulator spring will have no real effect on your shift points a side from were their suppose to be, so it won't hurt anything to do that, you should definately think about a pressure regulator system change while your in there. Not to be pushing Bruce's stuff but he's the only one I know that sell the complete system, or indvidually if you chose. It may help or even solve your problem not to mention the other benifits of stronger holding clutches and longer tranny life.

http://www.2004rperformancecenter.com/mcartfree/product.asp?intProdID=84

 

[68Camaro]

Mark and Jim,

Thanks again for you suggestions. I think we may be getting somewhere on this one now that I have a better understanding of how all the parts work together, your explaination is very helpful. I bet the lack of an increase in the 1-2 pressure is causing the problem, or the majority of it.

I hope to get the time to pull the pan this weekend, I will let you know what I find.

Thanks,
Greg

 

[WE4]

Ck the Int boost feed tube on the VB very carefully. This is the most common problem with the symptoms you have. Next would be the 1-2 rev boost valve in pump. Like Mark said "whole thing or individually" but I will say your pressures are Low all around. Boost is just really weak but you could use a bit more across the board.

'However...........
it still will not cause the 1-2 shift to shift early. Just weak. Timing is gov oil vs tv modulated oil. True line is not a player here.

Good luck....

Bruce
WE4

 

[HOTTOGO]

Originally posted by WE4
. Next would be the 1-2 rev boost valve in pump. Like Mark said "whole thing or individually" but I will say your pressures are Low all around. Boost is just really weak but you could use a bit more across the board.

'However...........
it still will not cause the 1-2 shift to shift early. Just weak. Timing is gov oil vs tv modulated oil. True line is not a player here.

Bruce
WE4

Yeah what he said "Timing is gov oil vs tv modulated oil. True line is not a player here." is what I tried to say, by over theroizing it. I did suggest in an earlier reply he needs higher tv pressure.

Greg, I really think you should try the PR system first if you are going into the pan, it is by far easier than dropping the VB and then if it don't help, drop the VB. Hope fully you have a drain plug, if not maybe get that too.

 

[68Camaro]

Bruce and Mark,

Thanks for the additional information. I did not have time to drop the pan this weekend, unfortunately in an early Camaro the trans cross member goes under the pan. It takes sometime to get to the pan. Yes, I did install a drain plug and it makes this job much easier.

So, first I should check the feed tube. Can this be removed without removing the valve body? I believe Bruce has suggested using locktite to eliminate any potential leaks.

Second, the PR system. I have a .471 boost valve and heavier spring from the Superior kit installed, but just the stock Rev. valve. Should I consider a larger Rev boost valve? Also, is it possible the Rev boost valve is sticking in the bore of the case or does the outside piece stay stationary and only in inner piece moves? I will check pressures before removal of anything. What pressures would you expect to see with a .471 boost valve and stock Rev. boost valve?

Third would be the Upshift Mod Valve, can this be removed from the valve body without removing the VB itself? Not sure if there is any interference with other components. Checking my notes from the kit installation, my VB did not have the Upshift Mod Valve spring installed. Maybe it is just sticking???

Thanks again for your help.
Greg

 

[68Camaro]

I had alittle time last night, so I decided to recheck the pressures:

Park: Min TV 70, Max 225
Rev: 125, 250
3-4: 70, 250
1-2: 125, 125

At full TV, the needle on my gauge vibrated quite a bit and there was a noticeable "buzz". With a slight throttle increase it improved some but it was still present, what causes this?

In Drive at full TV I brought the engine up to about 2500 and the pressures dropped to about 150, is this normal or is the drop excessive?

The lack of pressure in manual 1-2 seems like a problem although I rarely use the manual mode, is this directly related to the Rev boost valve and/or the feed tube?

Thanks again for your help.
Greg