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Discussion Starter #1 (Edited)
Well after upgrading to the larger OEM style Dorman cooler almost 3 years and 20k miles ago, I was happy with the temps while towing. 195* max in all conditions. Our last trip has me wondering what is going wrong as the temps went close to 225 on our way home. On our way out we climbed and descended some good mountains when something strange happened, no engine braking in 1st. Other than those 2 issues, it seems to work fine. It has been suggested that my trans is on it's way out and that reverse may stop working soon as it shares parts with 1st. Have close to 130k miles on it now.

My fluid looks darker than new, but that may be normal, IDK. I replaced my spin on filter and cut it open and found no pieces of stuff. It does look kind of dark but it was not clogged by any means. See the pic with the fluid that came out of the filter also.

So after searching and reading many posts, this part may be suspect for the higher temps...the cooler bypass valve. I will probably do a flow test soon. Sonnax 3660502k would be the replacement kit. https://www.sonnax.com/parts/2078-cooler-bypass-valve-kit

As for no engine braking in first, I found another Sonnax part that might help, Low/Reverse Modulator Plunger Valve Kit Part No. 36947-06K. https://www.sonnax.com/parts/2101-low-reverse-modulator-plunger-valve-kit

Anybody think I'm on the right track to correct these issues or should I just be shopping for a whole new trans replacement?
Our get a way plans are on hold because of this...don't want to get stuck in the middle of nowhere with no options.
 

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Discussion Starter #2 (Edited)
Just tried the flow test and think it failed before it started on step 3? Anybody out there?

1. Get two containers, each at least a gallon. Get a friend to help.

2. Warm up the trans.

3. Remove the cooler line where it attaches to the rear of the trans. Point the line into the first container. At this point fluid dripped/streamed out of the trans pretty fast and it wasn't going to stop. After about a quart I reattached the cooling line and posted here. Does this mean the bypass valve is toast?

4. Have your friend start the engine, leaving it at idle in park.

5. As soon as the flow is steady (should only be 2-3 seconds) move the line to the second container. NOTE: If there is fluid spraying out of the transmission SHUT THE ENGINE OFF. This indicates the test has failed. A small drip, or even a few drips out of the trans is normal.

6. Keep the line in the second container for EXACTLY 15 seconds, then move it back to the first container and shut the engine off.

7. If there is at least one quart in the second container it passes and the flow is normal. If there is less than a quart, or there was a spray coming from the trans it fails the flow test.

A failed test means one of three things.

a, There is a restriction in the cooler circuit. This could be a damaged/kinked/pinched hose, debris in one or both coolers, or a damaged cooler.

b. The bypass valve on the side of the trans has failed. Rebuild kits are available. They are inexpensive and easy to install.

c. The pump is worn out. This is not very common, but it can happen.

The above test is credited to Mark K. here on the forums...
 

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no engine braking in 1st. Other than those 2 issues, it seems to work fine. It has been suggested that my trans is on it's way out and that reverse may stop working soon as it shares parts with 1st.
Does it have engine braking in 2?
3. Remove the cooler line where it attaches to the rear of the trans. Point the line into the first container. At this point fluid dripped/streamed out of the trans pretty fast and it wasn't going to stop. After about a quart I reattached the cooling line and posted here. Does this mean the bypass valve is toast?
No, it does not. That's probably fluid draining out of the cooler.
 

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Discussion Starter #4
Thanks and yes, braking in 2nd.

So the extra capacity in causing back flow due to gravity, as it's draining out the trans and not the line?
If that's the case, do I have to let the extra drain first?
 

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You don't have to let it drain. But if you get a big air bubble during the test it's going to affect the results.

No engine braking in 1 but it has it in 2 is most likely a low/reverse clutch problem. I think that means rebuild time. Sorry.
 
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At this point fluid dripped/streamed out of the trans pretty fast and it wasn't going to stop. After about a quart I reattached the cooling line and posted here. Does this mean the bypass valve is toast?
If the fluid was coming from the fitting on the transmission where the cooler line connects, the bypass valve is leaking.

I have also read discussions where it was stated that there was not enough oil pressure to the low/reverse clutches to use 1st gear for braking and that doing so would cook the clutches. Maybe Mark can comment on that.
 

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Discussion Starter #7
If the fluid was coming from the fitting on the transmission where the cooler line connects, the bypass valve is leaking.
Yes it is and that was my thought at first. Looking at it, it doesn't seem that easy to get to.

Wondering if I should (1) even think about replacing those 2 parts given the no engine braking in 1st or (2) should I wait until the truck won't move in 1st or R to confirm the need for a rebuild, or (3) just be proactive and rebuild or replace now?
 

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Yes it is and that was my thought at first. Looking at it, it doesn't seem that easy to get to.

Wondering if I should (1) even think about replacing those 2 parts given the no engine braking in 1st or (2) should I wait until the truck won't move in 1st or R to confirm the need for a rebuild, or (3) just be proactive and rebuild or replace now?
It's easy to remove the bypass tube. You unscrew the two fitting that the cooler lines connect to and the bypass tube comes off with them.

As for what to do about the transmission, if it was my truck and I thought I had cooked clutch pack, I would want it fixed.
 

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Discussion Starter #9
Yeah, me too. There are fish waiting to be caught and woods needing to be camped in...

So the next question is have it repaired or replaced? I should probably get a new TC also, nothing wild, just new.
 

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Discussion Starter #11
For peace of mind maybe go with a Ford HD unit with a good warranty across the nation? Unless there is a rebuild option that also gives that peace of mind...
 

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So the next question is have it repaired or replaced?
The difference is in the people that rebuild it, whether or not you're replacing it. You will NOT get a new trans for this, it's going to be a rebuilt unit. Does it matter if it is a rebuilt core from someone else, or if it is your trans that is rebuilt? In my opinion, it's the same thing either way. It comes down to price, who you can trust, and the warranty.

I should probably get a new TC also, nothing wild, just new.
Only if you want the new trans to last more than a week or two. Using a trans off a failed transmission gaurentees that the new transmission will fail, too.
 
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Discussion Starter #13
Well I know a great trans builder but he's backlogged and I want to reduce down time. Maybe if he has a core that would save some time. I'm not attached to my core very much...
I also have a Ford dealer a mile away but have seen mixed reviews about their reman HD units. I do like the idea of their network across the country. Those units come with a decent TC, IIRC.
Then there are the few recommended ones people like here, but shipping cost and time add to the price. And if something goes wrong, how to get it fixed?
Anybody got a recommendation for a good shop in Albuquerque?
Any other ideas?
 

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Discussion Starter #14
As for no engine braking in first, I found another Sonnax part that might help, Low/Reverse Modulator Plunger Valve Kit Part No. 36947-06K. https://www.sonnax.com/parts/2101-low-reverse-modulator-plunger-valve-kit
I'm surprised that nobody thinks this is a culprit...did anybody read the symptoms it cures?
'The Low/Reverse modulator valve is prevented from properly supplying regulated line pressure to the Low/Reverse clutch, which can cause slippage, burnt clutches, and loss of engine braking.'

And I do think the flow test failed since it would not stop leaking out the trans past the valve.
 

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I have no experience with that Sonnex part. I think it's worth a try. Also get a bypass rebuild kit, they are cheap and easy to install.
 

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Discussion Starter #16
This just in...I spoke to the hydra chip folks who said,
"We don't hold the converter or coast clutch in lower gears. Not really good for the transmission. Is designed to hold in 4th and 3rd, with some degree of hold in second. However, it'll let out once the RPM drops below 1100 RPM or 24 MPH."

So it looks like my 1st gear engine braking problem is non-existent. One down, one to go.:smile2:
As for the higher temps, it's looking like the coolant bypass valve is the culprit and I should get one to R&R.

I did find an ATRA shop in town that for $49 will check for codes, check the fluid and test drive it. If I need a trans they have one for about $3k with a nationwide warranty of 3yrs/100k miles. Now I wondering if I should even visit them until after I change the valve.
 

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Change the bypass valve first. You may not have any problems after that.

I agree with not locking the converter or engaging the coast clutch at low RPM. There isn't enough pump capacity to handle that.
 
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Discussion Starter #18 (Edited)
Shopping around I was thinking of going with this since I have to remove it anyway. Might as well make it easier.
[ame]https://www.amazon.com/gp/product/B000NS6HRE/ref=ox_sc_act_title_1?smid=A3B850ZGIPDG3A&psc=1[/ame]
BUYER BEWARE, THIS PART TURNED OUT TO BE COUNTERFIET, DO NOT BUY THIS PART!

Speaking of easy, access is not so easy due to the exhaust pipe and especially the heat shield. Any advice?
 

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That looks like the way to go. I haven't changed one that was installed in a truck so I'm not going to be much help with that.
 

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Discussion Starter #20
Local ford dealer wants about $4400 for a trans swap, lol
Anybody change out the bypass assy, still on the truck, lately?
 
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