4R100 Transmission Shift Issues.

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Feb 23, 2011 | 05:04 PM

mustangx

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4R100 Transmission Shift Issues.

The trucks having issues shifting once warmed up. When cool it runs and shifts perfectly fine, once warmed up it won't shift easily out of first gear. I can horse it into 2nd by bringing the rpm's up to 3000 letting off the accelerator then applying the accelerator again and it shifts into 2nd at about 2200 rpms. The remaining shifts go smoothly. To date I've replaced input and output shaft sensors, vehicle speed sensor on rear dif, Solenoid pack, tested the harness, rebuilt the transmission and installed a shift kit and upgrade kit to the accumulator and valve bodies, Replaced the PCM today and not 1 thing I have done has made the slightest difference. It's all relevant to temperatures but nothing is getting hot, tranny is averaging 135* Once the trucks actually hot (tranny temp 145*} after say plowing snow for an hour it will not shift at all out of first, all I get is reverse and first gear until I cool down for 25 minutes then it shifts itself perfectly fine til it gets warm again and the cycle starts all over again.

Feb 23, 2011 | 06:03 PM

PwrHngry

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From: Beautiful Winder, GA

First, have you tried returning the truck back to stock to see if the problem clears up? I'm assuming that if you replaced the PCM then you probably tried running the truck stock, but I could be mistaken.

As for replacement of parts, I'm again assuming that all the parts replaced (solenoid pack, shift kit mods, etc.) were in an attempt to rectify the issue? Normally I'd suspect a valve body issue, but since that was modified then it's an unlikely suspect. Maybe the EPC valve is failing as the tranny heats up and is not able to maintain adequate line pressure in the tranny, but that's a tough call without some diagnostic equipment.

I'd give BTS or John Wood a call and see if they can help offer a solution. It may be something they've seen before and have a simple answer.

Good luck!

Feb 23, 2011 | 06:29 PM

mustangx

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Thanks for the input PwrHngry , Yes I've tried all the tunes on the programmer as well as stock. None made any difference at all. John Woods suggested the front Pump which I had changed, Bts never returned my call and were unable to help me over the phone the 2 times I tried them. I'm not familiar with the EPC and a quick google describes it as the solenoid pack I replaced

Feb 24, 2011 | 06:24 AM

gbroehl1

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From: Connecticut

here's a bump for ya.

Feb 24, 2011 | 09:23 AM

Robert6401

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That sounds like what my stock trans was doing when it failed. The clutch packs were worn. I now have a JW trans.

Feb 24, 2011 | 04:38 PM

mustangx

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When I went into this I wasn't sure if i needed a transmission a PCM a harness or what, and dropping 4k on a transmission wasn't an option. My tranny guy is absolutely positive the transmission is 100% up to par now after his rebuild. He drove the truck home last nite with his scanner on it and noticed a small voltage drop finally with the questionable shift issue related to the selector switch which was replaced,, so now he thinks it maybe a broken/corroded wire in the harness that when cool tests fine but when warm is having some loss. We had the harness out and had gone over it carefully but he wants to pull it again.