TH350 delayed manual 1-2 shift - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-06-2008, 11:58 AM
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TH350 delayed manual 1-2 shift

Hello guys.

I have a 1965 Cutlass with a 330 and TH350. The transmission is stock, no shift kit or anything special. It was rebuilt 4 years ago, since then I have changed fluid and filter 3 times. It has around 5k miles on it. It has a new Hughes 2500 torque converter.

When I put it in DRIVE it works perfectly. WOT shifts 1-2 at 4200 rpm and 2-3 at 4500 rpm. Shifts smooth at part throttle and firm at WOT. Kickdown downshifts work flawlessly too.

The thing is I want to shift at 5000 rpm when I'm going for it, so I thought I could shift it manually. But when I shift manually from 1-2 I have a delay for at least a second. Once the delay is over it shifts perfectly. Furthermore, the 2-1 manual downshift is instant but really hard.
Manually shifting 2-3 and 3-2 are instant and perfect. All this happens during both WOT and part throttle driving, regardless of road speed.

I tried unhooking the kickdown cable (which is correctly adjusted) - no change. I tried different settings on the vacuum modulator - no change.

Any ideas why this is happening?

Thanks!

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Old 10-06-2008, 07:29 PM
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that is what the shift kits allow you to do, drive it like a stick...You can do a kit without pulling the trany.
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Old 10-06-2008, 08:00 PM
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There are two holes that are dilled to firm up shifts. They are the "feed" holes. I believe I have them shown on another post here, but there are a couple of others above the manual valve in the valve body that can also be drilled to feed more volume to the shift valves.
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Old 10-07-2008, 12:35 AM
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Thanks for the replies.

Quote:
There are two holes that are dilled to firm up shifts. They are the "feed" holes. I believe I have them shown on another post here, but there are a couple of others above the manual valve in the valve body that can also be drilled to feed more volume to the shift valves.
So are you saying this delay is normal operation? Even if it ONLY is present during shifting from manual low to manual second. And while there is a delay, when the shift finally occurs it is good and firm.

There is one way to get rid of the delay. If I take it up to let's say 3000 rpm in manual low, then shift into manual second while I quickly let up on the throttle, it will upshift instantly. But this kinda defeats the purpose.
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Old 10-07-2008, 02:19 AM
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Read through this Info by Jakeshoe and you should find what you need.
http://www.hotrodders.com/forum/th35...ch-145361.html
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Old 10-07-2008, 02:53 AM
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Thanks, will do.
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Old 10-07-2008, 03:12 PM
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Ok, so I have read the thread. Very impressive, that's some good info. Great pictures too.
However I still don't know what's causing my problem. I think it has something to do with the valvebody, like sticky valves or something. That wasn't covered much in the thread.

Quote:
There are two holes that are drilled to firm up shifts. They are the "feed" holes. I believe I have them shown on another post here, but there are a couple of others above the manual valve in the valve body that can also be drilled to feed more volume to the shift valves.
My shifts already are firm enough. I took a drive the other day and at the 1-2 shift the car ripped the tires loose (I admit it was raining, but still it's just a 330). If I had too little volume/pressure going to the shift valves wouldn't the shifts be soft?
I'm wondering, are there any valves that only are used during manual low/second? For example, what does the manual low control valve do?
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Old 10-07-2008, 03:26 PM
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I don't know much about how all the fluid circuits work. There is a Governor Recalibration kit that allows you to fine tune the automatic shift rpm. It doesn't affect manual shifts tho'. You use lighter weights & springs for higher rpm shift points.

http://store.summitracing.com/egnsea...115+4294904013
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Old 10-07-2008, 04:38 PM
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I'm not at home now to look at a seperator plate and the hydraulics to show you which holes may be a restriction.

What I'm trying to explain is that there are two holes that are at or after the shift valves that are normally drilled to allow a firmer shift. One for the shift into 2nd, another for the shift into 3rd.

However the holes that feed fluid TO the shift valves (not after) may be a restriction and be causing the shift valve to open slower causing a delay from the manual valve.

I was studying the TH350 circuits extensively a couple of weeks ago to sort out a problem and there are a couple of small holes in the seperator plate just above the manual valve in the valve body that are feeds to the shift valves/circuits.

TransGo has you drill these on the TH350C Reprogramming kit, because you re-use the stock seperator plate. However they supply a new plate on the non-lockup TH350 so they are already larger IIRC.

I do my own VB mods on these and I drill 4 holes in the plate to .125".

It most likely is a delay in the fluid movement through the VB on the manual shift, and can probably be solved with some orificing changes.

I would look at it in more depth if I had the pieces in front of me but I don't right now and won't for a couple of weeks.
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Old 10-08-2008, 01:09 PM
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Quote:
What I'm trying to explain is that there are two holes that are at or after the shift valves that are normally drilled to allow a firmer shift. One for the shift into 2nd, another for the shift into 3rd.

However the holes that feed fluid TO the shift valves (not after) may be a restriction and be causing the shift valve to open slower causing a delay from the manual valve.
Ok, that makes sense. But couldn't enlarging the holes TO the shift valves also lower the shift points (since that would create higher pressure at the shift valves at any given rpm)? On the other hand, if that is how TransGo does it the answer should be no right? Doesn't seem likely that a performance shift kit would lower the shift points in DRIVE.

Anyway, thanks everyone (especially jakeshoe) for taking the time to respond to my questions. I appreciate it guys!
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Old 10-08-2008, 06:23 PM
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No, it won't change the rpm, that is controlled by modulator and governor oil and those are seperate circuits that act on the shift valves. They aren't so much a "volume" circuit as a pressure circuit to allow the valves to move or not, the oil that feeds the clutch apply and also the accumlators at the same time are a volume circuit at the time of the shift, and after it is completed would be more of a pressure circuit.
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Old 10-10-2008, 12:45 PM
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Quote:
No, it won't change the rpm, that is controlled by modulator and governor oil and those are seperate circuits that act on the shift valves. They aren't so much a "volume" circuit as a pressure circuit to allow the valves to move or not, the oil that feeds the clutch apply and also the accumlators at the same time are a volume circuit at the time of the shift, and after it is completed would be more of a pressure circuit.
Alright, tricky little things these transmissions...
I'm thinking - if I open it up and modify the separator plate I will need gaskets and fluid etc. Since a shift kit is only 40-50 bucks maybe I'm better off just installing one of those? The results would probably be much better, given my limited experience with these things.

I've heard good things about TransGo, would that be the way to go? I'm thinking about their 350-1&2 Reprogramming kit. Would that cure the 1-2 shift delay? I would like hard, firm shifts but not neckbreaking ones.
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Old 10-10-2008, 04:03 PM
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If you get the Governor Recalibration Kit it would allow you to leave the trans in Drive & let the trans shift automatically for better consistancy once you set the shift rpm you wanted with the springs & weights. The TransGo Kit should give better performance also.
http://www.transgo.com/rpg_generalmtr.php
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Old 10-11-2008, 12:52 PM
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Quote:
If you get the Governor Recalibration Kit it would allow you to leave the trans in Drive & let the trans shift automatically for better consistancy once you set the shift rpm you wanted with the springs & weights. The TransGo Kit should give better performance also.
Yeah, but I don't race so consistancy isn't that important to me. I actually like the stock shift points (4200-4500) for everyday driving because then I can drive around/floor it/whatever and still be kind of easy on the engine.
And shifting on your own when you really go is fun! (Until you overrev it...)
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Old 10-11-2008, 01:21 PM
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The TransGo reporgramming kit for the TH350 is an excellent kit. I install it as per the instructions and drill the feed holes ever so slightly larger. I think they are slightly conservative with the shift calibration.

I rarely use them anymore though. Only for customer installs on an already assembled trans built elsewhere.
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