Hemi conversion w/transmission problems..Help me, please. - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 4 Old 11-30-2013, 04:21 PM Thread Starter
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Hemi conversion w/transmission problems..Help me, please.

I am somewhat mechanically inclined but this is over my head and I blew my budget buying a Jeep that the previous owner said "Runs perfect and has been checked out by mechanics and is tip-top shape!" It is a used Jeep JK Unlimited Rubicon with a 5.7 Hemi conversion, with the 545RFE tranny. It is a Jeep Speed Shop kit that was stuffed in by TUNEX in Bountiful, Utah. I actually flew from NY to Utah to pick this up and drive it home. As I left Salt Lake City, I stepped on it to pass someone and the engine just revved, like the transmission went it neutral. I backed down to half throttle and the tranny acted as usual. I pulled over, checked the tranny fluid and it was fine. I tried punching it again and it did the same thing. When taking off under full throttle it accelerates good for a short period then then it revs up again and won't shift until I back down on the throttle. I stopped at Trail Jeeps in Golden Colorado to get their opinion and to have the ECM scanned and they pulled the following codes; P0706 -transmission range sensor circuit performance, P0958 - Auto Shift Manual Mode Circuit High, P0850 - Park/Neutral Switch Input Circuit and P2704 - Transmission Friction Element 'E' Apply Time Range/Performance. They think it might be the valve body. I went to the Chrysler dealership and the valve body's are on back order and aren't even available right now. I spoke to a transmission mechanic, he said with the low mileage on this, he'd be surprised if the valve body was bad. I drove this 2500 miles home keeping it under half throttle with no issues. I have been playing phone tag with Todd at the Jeep Speed Shop and when I tried to call him today, his voice mail was full. Does anyone have any thoughts or suggestions regarding this? Any tests I should run?
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post #2 of 4 Old 12-02-2013, 06:43 AM
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In my experience with electronic controlled autos, having seen this problem with the high rev no go/med throttle go, it turned out to be a couple different things.

The first one, which had me super puzzled, was trash blocking valve body passages, not allowing proper pressure to go where it needed to be, giving the exact symptom you are having. It cleared itself (right after I dropped the rig off at the tranny shop, my tranny guy called and asked what the heck was wrong with the rig, it was driving just fine) with shutting it down and letting it set, and I guess the trash settled on the bottom of the pan.

The other was the TQ was gutted and sent aluminum shavings through the whole transmission, which, of course, required a full rebuild.

My suggestion is to first do a full tranny fluid flush. Just dropping the pan wont get it all, there is a machine that needs to be hooked up to accomplish this.

Prior to doing a flush, I would suggest dropping the pan to check for big particulates. A little bit of foreign material in the bottom of the pan that looks like graphite shavings (I mean SMALL, no bigger than a wet powder) is normal. Anything shiny, such as aluminum, you are in for a full rebuild.

Also, take and rub the fluid from the dipstick between your fingers. It should be nice and slick, not gritty at all. Take a flash light and shine it on the fluid on your fingers, if there is shiny stuff in it, get the tranny rebuilt.

Take a look at the fluid color, it should be bright red. Take a clean white cloth and wipe the dipstick on it and observe the color. Brownish/red = need new fluid/High heat conditions. High heat = death for an auto. 230 degrees, even with full synthetic is terminal, the viscosity will break down and cause similar symptoms to what you are experiencing.

Other things to check, make sure the tune is in sync with the tranny. Im not too familiar with the hemi fly by wire crap, but I know that there has to be a sync between throttle position and throttle body position or something like that (autos are still smoke and mirrors to me, but I know a little just from the 6 rebuilds my Dodge had to have and asking questions...).

Along with the other simple things, of course check the fluid level. You may simply be low, always check the tranny while the rig is running, in neutral. This absolutely could cause the symptoms mentioned, and low fluid will lead to tranny death due to high heat.

Check to make sure the external tranny cooler isnt blocked with gunk either. I always go for the biggest cooler I can, and separate from the radiator. You want the fluid to be as cool as possible, and running through a typical radiator it will be the same temp as the radiator. Should be a separate cooler every time. A trashed up cooler will block fluid from getting to where it needs to be in a high throttle situation. If it is full of gunk, find the reason for the gunk...probably leads to a full rebuild.

I hope some of the above helps out. Ill stay tuned. I have a couple other avenues to ask questions from a buddy of mine that has done several of these conversions.
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post #3 of 4 Old 12-02-2013, 07:33 AM
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I am not a transmission person but I can tell you what I have learned while doing research for the Hemi conversion I just did. First off I would contact Todd at JSS and see if he is familiar with the Jeep. Todd is a good guy and has always seemed happy to help out. I would also contact the shop that did the conversion to find out what year and model trans is installed in your JK
also see if an older valve body was installed in a newer model transmission.
Todd was telling me that the he was having success using later model 5-45 transmissions and even the 6-45 transmissions successfully by using valve bodies from older model 5-45 transmissions. Maybe it is possible that incompatible were used - This is where I would start
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post #4 of 4 Old 12-02-2013, 10:24 PM
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Quote:
Originally Posted by Hagsjeep View Post
I am somewhat mechanically inclined but this is over my head and I blew my budget buying a Jeep that the previous owner said "Runs perfect and has been checked out by mechanics and is tip-top shape!" It is a used Jeep JK Unlimited Rubicon with a 5.7 Hemi conversion, with the 545RFE tranny. It is a Jeep Speed Shop kit that was stuffed in by TUNEX in Bountiful, Utah. I actually flew from NY to Utah to pick this up and drive it home. As I left Salt Lake City, I stepped on it to pass someone and the engine just revved, like the transmission went it neutral. I backed down to half throttle and the tranny acted as usual. I pulled over, checked the tranny fluid and it was fine. I tried punching it again and it did the same thing. When taking off under full throttle it accelerates good for a short period then then it revs up again and won't shift until I back down on the throttle. I stopped at Trail Jeeps in Golden Colorado to get their opinion and to have the ECM scanned and they pulled the following codes; P0706 -transmission range sensor circuit performance, P0958 - Auto Shift Manual Mode Circuit High, P0850 - Park/Neutral Switch Input Circuit and P2704 - Transmission Friction Element 'E' Apply Time Range/Performance. They think it might be the valve body. I went to the Chrysler dealership and the valve body's are on back order and aren't even available right now. I spoke to a transmission mechanic, he said with the low mileage on this, he'd be surprised if the valve body was bad. I drove this 2500 miles home keeping it under half throttle with no issues. I have been playing phone tag with Todd at the Jeep Speed Shop and when I tried to call him today, his voice mail was full. Does anyone have any thoughts or suggestions regarding this? Any tests I should run?
Give me a call 707-338-3154 and i can HELP. I will be around to take your CALL.
I have some ideas.

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