I lost second a while ago, and I've finally figured out it's either a stuck valve or the 1-2 accumulator is shot (well.. not just figured it out, but I've finally got the ***** to act on my knowledge). I'm just wondering how tough a job it's going to be to get this thing out and replaced/repaired. I'm yanking the valve body within a couple days (after getting a 700r4 manual and possibly a shift kit (valve body will be out anyway, might as well)). Anyone with experience in this particular area, pointers and misc info would be greatly appreciated. Also, any other commonly problems I should see about preventive repair of?
Thanks in advance.

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'86 Camaro SC, black /w silver racing stripes
2.8l MPFI/700r4 /w special 2nd gear delete option
In search of new v8 engine & transmission, now contemplating t5 swap to get me out of this mess.
Misc Mods: Cut air box, '83 Firebird spoiler.
Performance Parts: MSD coil, Accel 8mm wires, SplitFire plugs, Gabriel hijackers.
Audio Mods: Pioneer DEH-P3000, two 12" Optimus Pro Audio subs in hand-made enclosure each powered by a 260 watt Optimus amp. Working on shaving the box for weight.
My Homepage, with pics.

 

Let me get this straight: You have no second but you have third and fourth, right? Don't waste your time. The Reverse drum is probably dished instead of flat. This causes the 1-2 Servo to bottom before it can apply the band but the 3-4 Servo has more travel so it can still get the band on and since the torque load in 4th is lower than second it holds.

 

Holy.. .. a straight response from someone?! This is new to me on this issue.
Ok, well.. let me fully describe the situation then.

Known Fact 1: 2nd isn't fully gone. In fact, once in a while it shifts fine.. the likelyhood of it shifting is heat-related. Cold tranny, it shifts (usually). Hot tranny, forget it (usually).

Known Fact 2: 2nd, when it doesn't shift, acts just like first except it doesn't engine-brake. How this affects anything, I don't know.. just pointing out everything I can.

Known Fact 3: 2nd slips like a bitch, whether it actually shifts or tries and fails. When it actually shifts, it holds pretty well, but the slippage is noticable (cold tranny usually). When it just tries, as previously mentioned it's like first.. but the engine load tells me there's slippage (hot tranny usually).

Known Fact 4: Yes, 4th is fine. No noticable anything with 4th. It shifts. It holds. No problems. Previously mentioned lower torque load could account for this in the drum situation, but I know the band itself is good.

Also worthy of pointing out, she's had this problem for a while now, and I do my best to keep her out of even trying for 2nd as to preserve the band, but over the course of time, the problem got worse and worse until about 2 months ago, and the situation started improving.. just a weird note.

I got around to thinking a bit and I'm gonna have the line pressure tested before I yank the valve body, so I'll have a better idea then, but input based on the full symptom list is very appreciated.

 

You don't need to pull the valvebody to remove the 1-2 accumulator, its in a seperate housing held to teh case by 3 bolts. Its the 3-4 that you need to pull the valvebody.

As for your concern, I have never seen a "dished" reverse drum (the part that the band squeezes) but I have seen the "lug" ont eh band bust where the anchor pin goes causeing a very similar concern.

However, the "works great cold, sucks hot" has me wondering if maybe you don't have a bad seal in teh servo or something similar. The old 4T60's had problems w/ one of the seals "rolling" and when cold, it would be great, once fully warmed up, it wouldn't even pull foward.

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I have seen TONS of 'dished' Reverse drums. The band slips and it warps the stamped steel drum. Other times it will just chew the drum up if it goes metal to metal. You may not have noticed it since you have to put a straight edge against the drum to see it. Probably up to half of the 700's I see will have some warpage but will still work even if you miss it. It just won't last as long. Ever notice that sometimes the band is burned along the outside edge? Ever wonder why?

I stand by my initial diagnosis, especially since you say that it slips bad.

The inner seal on the 440-T4/4T60/E still has that problem but the Teflon seals on the Servo don't really give any problems like that.

 

Wow, it's great to know something else that I need to watch for!

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Aw geez; my 2nd gear slips. I guess this means it's warping the reverse drum, eh? I always suspected that the guy that rebuilt my trans didn't use a long enough of a 2-4 apply pin.

If I have the stick in OD, and press on the gas, and it downshifts by itself into second, it'll hold second for a bit, then slip. (It's not the TCC or anything like that.) Also, if I accelerate from a stop, even if it's an easy acceleration, and the stick's in "OD", the trans will complete the 1-2 shift, stay in second for a bit, then slip!

If I accelerate from a stop, and have the stick in 2nd, the 1-2 shift completes, and the trans holds second. I can then move the stick into 3rd, and I'll get the usual WOT 2-3 shift. GMTech told me a while ago that it might be the increased line pressure (with the stick in 2nd) that shoots the 2-4 apply pin further.

So when I plan for my rebuild, I should replace that drum, eh? How much are those things?

Hm; I wonder if that drum wasn't warped from the beginning...

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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

In manual 1 and 2, the pressure is increased to max so the band holds tighter and completes the shift- for now.

 

Weird. Sticking mine in manual 2 doesn't affect my shift at all, cold or hot.. I am going to remove the servo and accumulator and replace their seals. If that doesn't help, valve body. I appreciate your straight answers, transfixleo, but I just can't accept drum warp causing my symptoms since the difference when tranny is cold/hot is like the difference between day and night. I do, however, accept that having driven it for 8 months like this has probably not helped the band's or drum's life expectancy.

Thanks guys for your helpful ideas and comments. =)

------------------
'86 Camaro SC, black /w silver racing stripes
2.8l MPFI/700r4 /w special 2nd gear delete option
In search of new v8 engine & transmission, now contemplating t5 swap to get me out of this mess.
Misc Mods: Cut air box, '83 Firebird spoiler.
Performance Parts: MSD coil, Accel 8mm wires, SplitFire plugs, Gabriel hijackers.
Audio Mods: Pioneer DEH-P3000, two 12" Optimus Pro Audio subs in hand-made enclosure each powered by a 260 watt Optimus amp. Working on shaving the box for weight.
My Homepage, with pics.

 

Let me know what fixes it. I love to learn.

 

That maybe so, but working at a dealership, most of the transmissions I work on are '97 and later. Thats means the majority of the 4L60-E failures I fix are:

Worn out TCC regulated apply valve (valvebody)
Busted Reaction Sun Shell
For awhile, we had a rash of input thrust bearings and reaction planetaries.

Very rarely do we see band failures.

------------------
FREE CARFAX Record Check

If you live in Southeastern US, check us out!
South East Thirdgen

GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

Out of curiousity I have a theory about at least some of the Sun Shell failures (we see a ton of those too). Do you think it is related to high pressure modes due to 1870 problems (we see a ton of worn out VB's too)?
I don't see why this was never a big problem on 700/4L60's but is common place now other than this reason.