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Discussion Starter #1 (Edited)
Hi all, '97 4.6 sport
As the title says, it bangs (sometime violently) going from park to reverse.

A little backround: Recently had a complete overhaul w/ tourque converter and when I got it back, this started happening imediatetly. the guy said it was because of the idle sometimes being "funny on these fords). I explained that this had never happened before, but I was shined on about having the idle checked out. Idle is around 900 or so, a little high, but not bad.

Now driving it is OK as I first put it directly into drive with my foot on the brake, then put it into reverse and it's fine. This sounds like a solenoid or accumulator I'm just guessing, and I'm hoping it won't require removal of the tranny to fix it.

I'm not going back to these guys as the vibe there is one of shove 'em out the door and sue me if you don't like it. A lot different than when I walked in! So I'm hoping for an easy fix. Any suggestions folks?
 

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any modifications to the valve body?
 

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How are the u-joints?
 

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Since the OP has not posted again, this thread is starting to make me feel like the people "Peanut" is talking about. Right around 2:04 and on in the vid. (For those who like Jeff Dunham pls enjoy the entire vid, for those who don't 2:04 to about 2:15 and you'll get my point)

http://www.youtube.com/watch?v=eoE2cLSjUmo
 

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Discussion Starter #5
Well here's the "OP" responding. I seriously didn't think I'd get a response after watching over 60 views and 3 days of nothing back, I thought maybe I said something wrong!

So I kinda gave up looking but thought I'd check once more, glad I did. Thanks for the Jef Dunham link, I think he's great too, and I didn't see his lips move either :)

As for the U joints, they're fine thanks. The tranny guy said he changed something to prevent damage during hard down shifts, might have been some mod to the valve body, I don't know, but he's lost his franchise now and might even be out of business by now.

I went into this rebuild hoping for a mild "J" mod, but got junk and a shine-on.

I guess a hosed valve body could cause that hard slam from park to reverse. Is anybody on here still selling a valve body with the mild J-mod and whatever springs accumulator etc it takes to do it at a fair price? Please private message me, and I promise to watch for a response, and thanks to those who had worthwhile suggestions.

Peace
 

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Discussion Starter #7
Not knowing what he did to the valve body, the "plate kit" might not cure the problem. I'm thinking of pricing a remanufactured valve body to rule that out, and start from there.

I'm just trying to get good opininons on what else can cause that condition before I go the valve body mod route and end up not fixing the problem.

Any other thoughts on causes?

Peace
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Generally you drill the holes in the plate to a larger size to provide more fluid flow to the clutches and accumulators to make the shifts faster, reducing heat and wear.

He probably drilled the reverse engagement hole out way too large and did who knows what else. A new plate will probably cure the issue, but without knowing for sure what (and what else) may have been done... it's a crapshoot at best.
 

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Generally you drill the holes in the plate to a larger size to provide more fluid flow to the clutches and accumulators to make the shifts faster, reducing heat and wear.

He probably drilled the reverse engagement hole out way too large and did who knows what else. A new plate will probably cure the issue, but without knowing for sure what (and what else) may have been done... it's a crapshoot at best.
I thought JerryW said there is no too big for that hole; that the bigger the hole is the faster the engagement (not HARDER). The weird thing here is the OP said if he goes to Drive first BEFORE going to Reverse, it doesn't do it.

I've got some fluid path diagrams somewhere for the 4R70W I'm going to study to see if I can find what's going on. I'm wondering if the shop he brought it to left a check ball out somewhere.
 

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Correct. This is all he says about it

Jerry W. said:
For a faster reverse engagement there is a single hole that can be opened up in the separator plate. The larger the hole, the faster the engagement.

[...]

This hole size is not really dependent on horsepower. The above sizes are the minimum for that HP, but if you want faster reverse engagements, you can go to a larger size hole.
I won't say any more until we get a trans guru in here first, lol.
 

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Discussion Starter #11
Thanks guys, this is getting interesting. Whatever else he did to it, it didn't change anything else about the trans shifting that I can tell. He talked some about how hard it is for the tranny to down shift from OD to Low, as something in it has to stop and change direction?? So he might have done something to ease that process?? I saw somewhere that OD and reverse use the same gearset??? Possible connection... read below.

That was my original complaint and why I was looking for a MOD. When I put my foot into it some, to try and affect a down shift, it was so slow in reacting, I would push down more and more and by the time it finally shifted my foot was way into the throttle and that down shift was way dramatic and much more than I needed! In fact that shift was when the tranny first failed, (loud groan and slowed down sharply).

Still in all, I was very used to the down shift in previous A4OD trannys, which use a cable I believe, and don't make you wait and push more throttle than you need.

Is this TMI? I do get to ramble on some lately.
 

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Discussion Starter #12
Re: "The weird thing here is the OP said if he goes to Drive first BEFORE going to Reverse, it doesn't do it."

I should mention that if I linger more than a second in Neutral coming from Drive, it also slams going into reverse just like coming from Park to reverse. So in daily use, I shift quickly from D to R, and it's ok, firm but not a SLAM! At start up, I just quickly bypass R and N to D and then quickly back to R, (only way out of the garage):). So if I don't engage D, it's a slam either way I approach R

Did that clarify some?
 

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What is the job of the case to center support spring aka the "anti-clunk" spring? How harsh would shift engagement be if the spring was forgotten, being a common misplaced part? Just made a thread not too long ago about it digging into the case.

http://img809.imageshack.us/img809/788/clunkspringcase.jpg
 

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Is there any way you can get it on a lift and check the u-joints and the rear end? Those are probably where the noises are coming from.

Does it do is less after the car has been driven awhile (heating up the rear end lube)? Nobody mentioned it could just be backlash in the rear gears.

My 'Bird has the rear bushing is the tail shaft of the transmission getting pretty worn out - causes vibrations at highway speeds.
 

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Discussion Starter #16
Hey, thanks for the thoughts.

Given that it began immediately when I got it back, and they had to pull the driveshaft and possibly the rear end to remmove the tranny, I suppose it's possible, but it never exhibits slop during on and off throttle, and never slams directly into Drive. Having driven cars with both gear and u joint slop, I think I can recognize that problem, so I'm still thinking transmission. If not the valve body, what else could they have messed up on a rebuild? They did install an upgraded clutch pack (8 disc I believe). What else might be specific to reverse engagement??

At this point it's a crap shoot. I either go for a complete rebuild again at another shop, or nickle dime this one to death by starting with a new valve body and going to a rebuild after that:( Anybody else got an idea? Gurus Welcome!
 
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