Transmission problem when hot
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Transmission problem when hot
I have a 98 E250 with the overdrive transmission. I just put a Trans Range Sensor on it, works better but didn't fix the original problem. When the trans is hot it won't shift into reverse, cold/warm no problem, just happens when it's been driven about 10 miles or more. Any thoughts?
Lead Driver
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The transmission is controlled by the computer.
The computer operates electric valves on the valve body located on the bottom of the transmission (inside the pan).
A code should be present when the issue is present because the computer looks at the valve electrical operation current signiture as a way to tell when they malfunction.
The valves change fluid routing that in turn operates bands and clutches to make gear changes.
You may need the services of a good transmission shop to solve the issue.
Good luck.
The computer operates electric valves on the valve body located on the bottom of the transmission (inside the pan).
A code should be present when the issue is present because the computer looks at the valve electrical operation current signiture as a way to tell when they malfunction.
The valves change fluid routing that in turn operates bands and clutches to make gear changes.
You may need the services of a good transmission shop to solve the issue.
Good luck.
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Thanks Bluegrass 7, would that be the case even if it only happens when it's hot? I guess I need to put some more miles on it to see if I can get it to blow a code. Are there special tools involved in replacing the valve? I've rebuilt a boatload of manual transmissions (race sports cars), but never cracked open an automatic...is it as simple as swapping out a valve sounds like it should be? Although a valve does seem like it could be the culprit, it doesn't even act like it wants to do anything, no slipping or anything like that...acts like I put it in neutral.
Last edited by towvan; Jul 24, 2010 at 07:00 AM. Reason: new thought
Hotshot
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From: St Louis
If the problem is only in reverse, you likely won't get any fault codes. Reverse gear is purely mechanical and hydraulic and the computer neither controls nor monitors its application or performance.
When the fluid gets hot, it thins down. You may have an internal leak in the reverse apply circuit. When the fluid is cool, it is thick enough so that the leak doesn't bleed off the apply pressure fast enough to matter. When the fluid heats up, it escapes more rapidly through the leak and cannot build enough pressure to apply the clutches.
You will need the services of a transmission shop as BG7 suggested to either rebuild the transmission or to further diagnose the point where the pressure is bleeding off. A "wet" pressure test with the valve body removed can determine if the problem is in the valve body (moderately easy repair) or if the leak is deeper inside the transmission requiring a complete tear-down. If you have an appropriate hydraulic pressure gauge, you can take line tap readings that will give insight into the condition of the internal hydraulics.
You might get lucky and find that it's a clogged or ill-fitting transmission filter. That one is relatively easy to remedy by a DIYer.
When the fluid gets hot, it thins down. You may have an internal leak in the reverse apply circuit. When the fluid is cool, it is thick enough so that the leak doesn't bleed off the apply pressure fast enough to matter. When the fluid heats up, it escapes more rapidly through the leak and cannot build enough pressure to apply the clutches.
You will need the services of a transmission shop as BG7 suggested to either rebuild the transmission or to further diagnose the point where the pressure is bleeding off. A "wet" pressure test with the valve body removed can determine if the problem is in the valve body (moderately easy repair) or if the leak is deeper inside the transmission requiring a complete tear-down. If you have an appropriate hydraulic pressure gauge, you can take line tap readings that will give insight into the condition of the internal hydraulics.
You might get lucky and find that it's a clogged or ill-fitting transmission filter. That one is relatively easy to remedy by a DIYer.
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Thanks ProjectSHO89, that makes perfect sense, I couldn't think of any reason it would only do it when it's hot. It has 232K on it and wasn't sure about the trans fluid, so I changed it with a filter...could be I didn't get it snapped in right, I'll give the filter a shot then take it to a trans shop when that doesn't work...
Thanks again.
Thanks again.
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