viven44 Posted May 14 Share Posted May 14 Hi all, looking for advise on how to approach this You may remember but I swapped a 460 from a 86 F250 into a 78 Bronco recently and I've driven it may be 100 miles so far... I used the torque converter from the 86 pickup as it looked brand new vs. the torque converter that was on the Bronco... maybe this was a bad idea.. fluid and filter changed at the same time. Up until now I haven't had any issues.. Both 2WD and 4WD.. Unfortunately I have a problem now (both in 4WD and 2WD)... transmission was the only thing I hadn't touched on this Bronco.. except the fluid and filter change.. didn't mess with seals or pumps... but I really did expect problems as the previous owner went and did some aggressive mudding which I understand caused the radiator to clog up and cause the previous engine (a 400) to overheat (most likely the transmission as well). It was a coin toss. The transmission whines when hot and losing all gears. It might limp along just enough to make it to my garage if close. Else, I have to let it sit for about 10 minutes and then I'm back to normal for a few miles. I have verified I have good fluid pressure through the cooler when cold. Basically have a lot of fluid leaking out of both cooler input and output when the lines are loosened individually. When hot, this behavior changes completely... there is very little fluid coming out of the cooler output... but when I loosen the cooler line input, I have good fluid flow out of the input and OUTPUT as well.... Why this behavior only when hot ? video below shows the whine.. whining when in park or neutral but goes away in gear.. but I don't know if this is consistent all the time Link to comment Share on other sites More sharing options...
mat in tn Posted May 15 Share Posted May 15 I would suggest running a line in lieu of the in-radiator cooler and see if the whine goes away. if it does then you may need a radiator. this does not exclude the trans but a clogged cooler can kill a trans. Link to comment Share on other sites More sharing options...
viven44 Posted May 15 Author Share Posted May 15 I would suggest running a line in lieu of the in-radiator cooler and see if the whine goes away. if it does then you may need a radiator. this does not exclude the trans but a clogged cooler can kill a trans. Thanks Matt. Before I put everything back together, I did flush everything out with compressed air. There is no clog when things are cold. It flows well. But maybe not well enough ? I happen to have an aux trans cooler. Maybe try that ? Link to comment Share on other sites More sharing options...
mat in tn Posted May 15 Share Posted May 15 Thanks Matt. Before I put everything back together, I did flush everything out with compressed air. There is no clog when things are cold. It flows well. But maybe not well enough ? I happen to have an aux trans cooler. Maybe try that ? absolutely. a simple short bypass will prove enough of a noise check and that is mostly what I was suggesting as a means of finding a direction. Link to comment Share on other sites More sharing options...
viven44 Posted May 15 Author Share Posted May 15 absolutely. a simple short bypass will prove enough of a noise check and that is mostly what I was suggesting as a means of finding a direction. I was thinking along those lines as well. Just to be sure, will I test with the short bypass the entire time or just when it starts acting up ? Link to comment Share on other sites More sharing options...
mat in tn Posted May 15 Share Posted May 15 I was thinking along those lines as well. Just to be sure, will I test with the short bypass the entire time or just when it starts acting up ? well. you explain it as an overheating transmission. so having more cooling is the most important thing. a simple bypass is only to prove the viability of the rest and see if the cooler might be the issue. Link to comment Share on other sites More sharing options...
viven44 Posted May 15 Author Share Posted May 15 well. you explain it as an overheating transmission. so having more cooling is the most important thing. a simple bypass is only to prove the viability of the rest and see if the cooler might be the issue. Another possibility I just thought of. When this Bronco was sitting for a few years, just about every vent hose on the drivetrain was clogged with mud dauber 'stuff'. Does the C6 have a vent ? If it does, and it is clogged, can the fluid build up pressure internally which causes cavitation and/or even flow issues from the oil cooler return ? The transmission had all kinds of leaks before... like where the shifter lever installs. The O-ring was flat out missing. All these were breathing passages. When I got the vehicle, I noticed the old transmission dipstick was stuck open. It wouldn't go down all the way. I swapped out this tube from the 86 so the dipstick was a tight fit. Maybe it ran all that time without issues due to this and I have made the transmission "too tight". It has zero leaks anywhere. The pump I assume needs suction ultimately (like a fuel pump)... maybe a wild hypothesis. I have also been beating myself up on whether I set the torque converter correctly ? I thought I did. 3 clunks, measured the inset. etc, made sure it matched what I measured on both the trucks. Since its a issue 'when hot' maybe not a problem here. Link to comment Share on other sites More sharing options...
FordFETruck Posted May 15 Share Posted May 15 Another possibility I just thought of. When this Bronco was sitting for a few years, just about every vent hose on the drivetrain was clogged with mud dauber 'stuff'. Does the C6 have a vent ? If it does, and it is clogged, can the fluid build up pressure internally which causes cavitation and/or even flow issues from the oil cooler return ? The transmission had all kinds of leaks before... like where the shifter lever installs. The O-ring was flat out missing. All these were breathing passages. When I got the vehicle, I noticed the old transmission dipstick was stuck open. It wouldn't go down all the way. I swapped out this tube from the 86 so the dipstick was a tight fit. Maybe it ran all that time without issues due to this and I have made the transmission "too tight". It has zero leaks anywhere. The pump I assume needs suction ultimately (like a fuel pump)... maybe a wild hypothesis. I have also been beating myself up on whether I set the torque converter correctly ? I thought I did. 3 clunks, measured the inset. etc, made sure it matched what I measured on both the trucks. Since its a issue 'when hot' maybe not a problem here. Yes, the C6 has a vent. It's about midway on the case if I remember right on the passenger side. It's a metal hole with a crimped over metal cap like you'd see on some differentials. Link to comment Share on other sites More sharing options...
viven44 Posted May 15 Author Share Posted May 15 Yes, the C6 has a vent. It's about midway on the case if I remember right on the passenger side. It's a metal hole with a crimped over metal cap like you'd see on some differentials. Thanks I think I found it. It is impossible to reach anymore ! Need the exhaust pipe out of the way. Link to comment Share on other sites More sharing options...
viven44 Posted May 15 Author Share Posted May 15 Thanks I think I found it. It is impossible to reach anymore ! Need the exhaust pipe out of the way. Negative on both of them. Tried venting with dipstick out and also tried a bypass hose at cooler. Pump whining starts when things get warm. Link to comment Share on other sites More sharing options...
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