Th200r4 first to second shift problem

Btw I also did a road test by disconnecting the TV cable, and gently accelerated the car and it did shift out of first gear without backing off the throttle, but it only changed up to second at 4,500 rpm then it short shifted 2-3-4 almost instantly!
 
I'm sorry, I take it that you are asking me to subscribe to the site?

I was told to post on this forum by the corvette forum as you guys over hear are helpful.
I've only posted one thread and it seems I've outstayed my welcome already as an unpaid member.

Thanks to all the guys who took the time and posted constructively it was appreciated. :)
 
Hey, knodty, you are welcome here. He was subscribing to this thread, and by him posting the site sends him notifications when there are additional posts.
Guys don't live on here(well some of us do) so sometimes it takes a bit to get a response to your probs. This is reguarded as the best 2004r forum for a reason. I feel we have the top builders of 2004r who post and answer questions and they are busy with their business so I am grateful they take their valuable time to field questions.

Posted from the TurboBuick.Com mobile app
 
The symptoms you describe indicate failing 2nd band. Once the shift is made does it downshift to first when you apply power?

Posted from the TurboBuick.Com mobile app
 
Sorry for misunderstanding!

It will only shift down to 1 if I'm doing less than about 45mph.
Once I back off the throttle completely otherwise it will not shift up, at about 4,500rpm.
It will shift down to 1 even from 4 under light throttle at 45-50 mph above that it be haves as it should!


Would a failing 2nd gear band effect/cause low 1st gear pressure.

Once again sort for any misunderstanding I really need to get up to date with forum talk.

Cheers guys :)
 
Knodty said:
I'm sorry, I take it that you are asking me to subscribe to the site?

I was told to post on this forum by the corvette forum as you guys over hear are helpful.
I've only posted one thread and it seems I've outstayed my welcome already as an unpaid member.

Thanks to all the guys who took the time and posted constructively it was appreciated. :)
Click to expand...
Yea sorry,i subscribed to the thread because I have a similar problem in one of my cars and I wanna see how the problem plays out...
 
Above 45-50 your in 3rd. I am still on band failure. Everything you describe points to that.

Posted from the TurboBuick.Com mobile app
 
Would a failing 2nd gear band effect/cause low 1st gear pressure, as I'm not sure how these things work and just need to get my head round it.
:)
Or would the low pressure cause the band not to grip properly?
P.S.
Under CRUISE throttle I will be in 4th at 45-50mph and if I hit the throttle half way down it will jump down to 1st, whereas before the problem it would only drop down to 2nd or 3rd depending on the throttle position, but above 50 it will perform normally.
:)
 
Last edited:
I'm no expert but when I had a late 1-2 shift it was because I sheared in half the band anchor pin. A new one made from billet metal cured the problem.
 
Knodty said:
Would a failing 2nd gear band effect/cause low 1st gear pressure, as I'm not sure how these things work and just need to get my head round it.
:)
Or would the low pressure cause the band not to grip properly?
P.S.
Under CRUISE throttle I will be in 4th at 45-50mph and if I hit the throttle half way down it will jump down to 1st, whereas before the problem it would only drop down to 2nd or 3rd depending on the throttle position, but above 50 it will perform normally.
:)
Click to expand...

The answer is no. A failing 2nd gear band will not cause low manual 1st pressure. Although Low pressure will cause the band to slip. There are many reasons you could have variance from manual 1 and manual 2. Typically it can be manual valve or VB wear. The boosted pressure from manual 1 and manual 2 comes from the same source and is boosted on the TV boost valve side of the Reverse boost valve. This is supplied by the steel transfer tube that is on the VB. The reason you have no TV increase in these gears is the manual 1-2 Boost pressure cancels out the TV pressure. This information and $2.41 will buy you a cup of coffee at Starbucks and give you absolutely no clue as to what is going on. You asked for it so there it is. On to the problem.

You're confusing line pressure with TV pressure. When you hook up your gauge you see line pressure. TV pressure is regulated to 90psi and is a variable pressure feed based on the position on the Throttle Valve. This controls 2 things. TV boost and Governor pressure. With the transmission is manual 1 and 2 cancels out TV boost pressure. What you cant see is the TV pressure. It still operates at 90psi the same, regardless of Main line pressure. Armed with this info why do I think your 2nd band is failing?

When the transmission shifts from 1-2 the only thing that is needed is the BAND TO APPLY. If the BAND DOES NOT APPLY you are still in 1st gear. This does not mean that the transmission did not make the shift, it simply means THE BAND DID NOT STOP THE DRUM. It could be either or but most likely the latter. The BAND MUST STOP THE DRUM TO ACHIEVE 2ND GEAR. Now with the explanation of TV pressure as the throttle is applied the TV pressure rises causing an increased shift RPM. Your still climbing in 1st gear (THE BAND IS NOT STOPPING THE DRUM ) you back off the accelerator TV pressure drops lowering the shift points causing the transmission to appear to stack shift. Its only stack shifting because TV pressure dropped and lowered the shift points. I asked if you could apply power after the shift. I don't remember seeing an answer but assuming when you do the transmission seems to downshift. BAND CANT HOLD THE DRUM so if drum not stopped transmission is in 1st. If you read threw all this what is the most common part that comes up more than once? THE BAND. Is it a guaranteed band failure? Absolutely not, but more than enough evidence points in that direction. In the mechanical world that's all we have to go on. Hope this helps.
 
Last edited:
Thank you for a very comprehensive explanation! :)

Once I back off the throttle completely at 4,500rpm or above, it will change up to second and if I accelerate not too hard and get the speed up to around 55-60 I can nail the pedal with no problem, but below 55-60 if I nail it straight after it has changed up it sometimes drops back into 1st.

I understand the basic principle now how it works and thanks again for your reply
:)
 
The transmission should never make a detent down shift from 45 mph to 1st. Will it make a firm full throttle shift from 1st to 2nd at any rpm? If the answer is no, I am once again back to the band. The pressure you listed at 190 psi is not enough for more than about 350-400 HP max IMO and I am not sure about that. Don't know how you will keep a band from slipping at that pressure.
 
No it won't shift from 1st - 2nd at any rpm under firm full throttle! So it looks like the band as you said! :)
When we first installed the trans it had pressures of about 240psi at full tv but I guess over the last 5 years and 15,000 miles it must of deteriorated.
The pressure at idle with TV pulled fully out was about 225psi ! Could it loose pressure through the system to only have 190psi when in drive?
Thanks
Peter
 
Knodty said:
No it won't shift from 1st - 2nd at any rpm under firm full throttle! So it looks like the band as you said! :)
When we first installed the trans it had pressures of about 240psi at full tv but I guess over the last 5 years and 15,000 miles it must of deteriorated.
The pressure at idle with TV pulled fully out was about 225psi ! Could it loose pressure through the system to only have 190psi when in drive?
Thanks
Peter
Click to expand...

Yes it could be a seal or something but I would say 5 good years has taken its toll on the pump. When the pump goes down hill they seem to go fast. Looks like time to freshen the old girl up.
 
Cheers thanks very much for your help and a great insight into how the th200r4 works
:)
 
I'd like to throw in a big thanks for the explanation of the stacked shift and possible band failure and their relationship to the pressure and tv modulation of it. Great Tech. Thanks.

Posted from the TurboBuick.Com mobile app
 
Well thanks for your help again guys and we will keep you informed as to what is wrong when we strip it down.
We took the trans out this morning and it only took us 1hr 50 mins once it was jacked up!
If the rebuild only took that long I would have it back in tomorrow lol

Cheers Guys
:)
 
You must log in or register to reply here.

Similar threads

M
06 Lacrosse CX problems downshifting from 2nd to 1st
Replies
0
Views
598
MoreQsThanAs
M
0-60n4
Not making the 1-2 shift at WOT
Replies
6
Views
695
0-60n4
0-60n4
B
Trans cooler lines to radiator question
Replies
2
Views
261
1KWIKSIX
1KWIKSIX
A
2004R With CK master rebuild kit, no 1-2 shift question.
Replies
13
Views
2K
AnthD
A
0-60n4
superjim's PCV catch can and evacuation system
Replies
4
Views
371
0-60n4
0-60n4
Top