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Discussion Starter · #1 · (Edited)
Finally got the car all together and took it out last night to see what it was like. I did a lot to it, gears, u-joints, fuel pump, jmod, torque converter, pi heads, new timing stuff, engine and transmission mounts, diff mounts, vacuum lines.
I had reverse twice when I backed out of the driveway, then ten minutes of driving later, I had no reverse. At first you could hear the car was in reverse, but it just revved without moving, though you could feel it sort of wanted to move. I tried a few more times to reverse, and now it felt like it was in neutral, (the reverse lights were on).
This morning I tried it again when it was cold, and idling in reverse it kind of wanted to crawl slowly backwards, but as soon as I revved it, it just free revs.
I also have no manual 1st, and no engine braking in manual 1st. In manual 1st while you are freewheeling instead of engine braking, if you rev the engine you can hear the transmission slipping instead of grabbing.
This no engine braking in manual 1st was happening before I did any work to the transmission, a pre-existing condition.
2nd 3rd and 4th gear all function correctly, and I am able to drive the car as normal.
My brief research leads me to believe that the 1st and reverse band is slipping.
I believe the new fluid is more slippery than the old dirty fluid, which enabled some friction which let reverse function.
I have just dropped a whole pile of money into the car, and a new transmission or a rebuild is just not an option right now for me, I am hoping at this point that I could just pull the transmission and dig into it as far as the reverse band and change that out.
Any advice would be appreciated.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Yeah it sounds like the reverse band is toast. 1st gear is just the forward clutch which, if it was fried, you would have more issues in the other forward gears as it's used all the way through 3rd. Pages 4-5 of Jerry's Thesis go into more detail.

It's rebuild time. I'd recommend you ditch the factory trans and rebuild a 99-02 (or 03 if you find one with the right OSS or don't mind swapping your original on).
 

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Discussion Starter · #3 ·
I have watched a few videos, and it seems that a guy could rebuild the 4r70w themselves, but just one part installed backwards etc would be a nightmare as you would probably only find it after reassembly. The reverse band doesn't seem too hard to get to, and even though it is only a band-aid solution, it would keep me on the road until I have that extra cash.
Apparently I like doing everything twice.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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There's no real point in pulling the trans and replacing JUST the reverse band and nothing else. You will need to replace all the seals (which, being 25 years old and already worn out, will get scored when the planetaries are removed to get to the internals). And not replacing the other clutches to basically "like new" the trans while it's out, given the minimal additional cost and labor involved (compared to pulling the trans) is just IMO asking for more trouble down the road. Since the 97 has the crappy one-way clutch and older valve body, you really should just get a newer core to rebuild and swap it in.
 

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You want to use a later tranny to rebuild, due to better parts.
The one-way clutches are much better after 01; 03 would be better, but you have to put in your original tailshaft.
New rubber seals everywhere, and the one piece-teflon seals, instead of the scarf-cut seals is a major improvement. for longevity.
I'm going to try an 02 with a 96 valvebody; /i've broke the new one by slamming it with the 2-3 accumulator, so you want the sonnax stiffening plate for under the 2-3; the 96 still has it factory.

Here's a good article on rebuilding it:How to: - 4R70W Transmission Rebuild Diary

Seems to me a broken one way clutch can do this; if it slipped on a really hard 1-2 shift, that could be it.
I've spun several, over the years.
 
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Discussion Starter · #7 · (Edited)
You want to use a later tranny to rebuild, due to better parts.
The one-way clutches are much better after 01; 03 would be better, but you have to put in your original tailshaft.
New rubber seals everywhere, and the one piece-teflon seals, instead of the scarf-cut seals is a major improvement. for longevity.
I'm going to try an 02 with a 96 valvebody; /i've broke the new one by slamming it with the 2-3 accumulator, so you want the sonnax stiffening plate for under the 2-3; the 96 still has it factory.

Here's a good article on rebuilding it:How to: - 4R70W Transmission Rebuild Diary

Seems to me a broken one way clutch can do this; if it slipped on a really hard 1-2 shift, that could be it.
I've spun several, over the years.
It is unfortunate that he deleted all the pictures in those threads, and each thread now just has one picture shown repeatedly, not showing the steps which he is describing.
I saw a particularly helpful series of videos which are very clear and concise, but I think that you must pay for the series to be sent to you.
Probably worth the 50.00 though for a step by step.
I have a spare functioning 1997 transmission here that may be my most cost-effective way to rebuild, knowing of course that I will not get the upgraded parts if I go that route.
 

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1995 Thunderbird LX 4.6 red
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It's possible that it is a band reverse band. And it's possible that the reverse clutches are bad. However, the first thing I would suggest is pulling the valve body down and removing and inspecting the reverse servo, the reverse servo spring and the reverse servo cover. The other guys are right about doing a rebuild and using a newer trans. However the reverse servo, cover and sprig are inexpensive. And I have seen several that the rubber gets so hard that it chips away and loses fluid pressure. If you don't have the money for a rebuild it's worth a look.
 
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Discussion Starter · #9 ·
Those valve body gaskets that have been through one heat cycle now, are they garbage if I drop the valve body again?
 

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if the gaskets have a crush line in them, you have to get new gaskets. wet the gaskets before you put them in.

I can still see the pix; I had to turn off the adblocker to get them.
 

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Discussion Starter · #11 ·
The reverse servo is either one two or three lines, and I cant tell which one until it is disassembled, according to the internet, which makes things a little more difficult in regards to downtime and my car sitting in someone else's driveway on Jack stands unless I buy all three.
Has anyone disassembled many of the thunderbird transmissions and can confirm or dismiss whether this is true?

:mad::mad:Cover and clip are available from ford, they don't have the servo anymore.

Haha. I tried to order from a transmission shop here in town, and he told me that I am wasting money trying to change the servo because the band is worn.
How much for a rebuilt transmission not installed? 2800 dollars.
 

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The forward clutch splines into the reverse clutch's frictions. so if the reverse clutch doesn't work, the forward clutch doesn't either..
 

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Discussion Starter · #13 ·
The forward clutch splines into the reverse clutch's frictions. so if the reverse clutch doesn't work, the forward clutch doesn't either..
Thank you.
I have got it figured that everything works except manual 1st and reverse, I have to find out which reverse servo to order, one, two, or three lines.
I guess that dirty dog or darrin aren't around these parts anymore, is there anyone else here who has disassembled many tbird 4r70ws who can tell me which servo I will need?
(Do they really individually measure each reverse servo needed? Seems time consuming for parts that are all manufactured to exact tolerances.)
If not, which online tranny parts stores are the cheapest so I can just order all three, because I cant disassemble my car in my friends driveway again, and then leave it there for a week or more until the parts arrive via courier, probably from the USA.
 

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1995 Thunderbird LX 4.6 red
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The reverse servo is either one two or three lines, and I cant tell which one until it is disassembled, according to the internet, which makes things a little more difficult in regards to downtime and my car sitting in someone else's driveway on Jack stands unless I buy all three.
Has anyone disassembled many of the thunderbird transmissions and can confirm or dismiss whether this is true?

:mad::mad:Cover and clip are available from ford, they don't have the servo anymore.

Haha. I tried to order from a transmission shop here in town, and he told me that I am wasting money trying to change the servo because the band is worn.
How much for a rebuilt transmission not installed? 2800 dollars.
Yes the reverse servo can have either 1,2 or 3 lines on the shaft. Most I've encountered have 2.I've seen several of later ones have 3, Think I've only ever seen maybe one servo with a single line on it. 1 is the shortest, three is the longest. You can buy a three, and if its a two you can grind the end down a little.
 
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Discussion Starter · #15 ·
I haven't torqued the valve body yet or put the pan on, but I am confident that I have fixed it.
The rubber on the reverse servo was broken in several places, and the covers rubber also had a tear.
I dug into a 1997 gran marquis 4r70w that I have, and pulled the reverse servo, which was a 2 line servo, my stock 97 bird also had a 2 line servo.
The unbroken servo is now in my bird..
 

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View attachment 45562 I haven't torqued the valve body yet or put the pan on, but I am confident that I have fixed it.
The rubber on the reverse servo was broken in several places, and the covers rubber also had a tear.
I dug into a 1997 gran marquis 4r70w that I have, and pulled the reverse servo, which was a 2 line servo, my stock 97 bird also had a 2 line servo.
The unbroken servo is now in my bird..
Very cool. That definitely can have an effect. Honestly I don't know if I've ever seen a bad Reverse band in a 4r70w. I've built plenty of them. But who knows. I'm hoping for the best for you.
 

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Discussion Starter · #17 ·
Manual 1st and reverse both work correctly, as do the rest of the gears. Will skid the tires gearing down to manual 1st.
I believe that the reverse servo was already on it's way out, due to the lack of engine braking in manual 1st that existed before I did the jmod. When I drilled the plate, I enlarged the reverse hole for faster reverse engagement, so when I put it back together it gave me reverse gear twice then blew the rest of the piston seal apart resulting in no more reverse or manual 1st.
There is quite a lot of that seal that was not even present anymore, it must have gone through the transmission at some point in time.
It is obvious to me that the other soft pieces in the transmission are in the same poor brittle condition as the reverse servo, and a rebuild is in my future, I am just thankful that I have bought myself some time to research and buy the correct rebuild kit.
Thank you to all who offered advice, and maybe this thread will help someone who experiences the same issues.
 

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If you find the best kit let me know because there is more than one out there. I can't afford a rebuild by a shop either. It is looking like I need to rebuild the transmission before my manual swap which is a shame.
 

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If you find the best kit let me know because there is more than one out there. I can't afford a rebuild by a shop either. It is looking like I need to rebuild the transmission before my manual swap which is a shame.
Best way to go typically is TranStar brand.
 
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Discussion Starter · #20 ·
Is there a kit that comes with everything you would need except for any hard parts that may be broken?
 
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