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8LL pops out of 3rd and 7th

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Any ideas on a fix for an 8ll that pops out of 3rd and 7th? its in a '96 RD688S

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Make sure all the bellhousing and clutch housing bolts are tight.

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All the 8LL's do that at some point.

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Shifter clutch, and or head gear. more than likely a worn or bent fork also.

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Our 8LL did that since it was new been to mack 4 times under warranty and they changed pop-it springs and balls each time while under warranty and then after warranty ran out they rebuilt the transmission and on the way home it jumped out again and they wanted us to pay the bill

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Any ideas on a fix for an 8ll that pops out of 3rd and 7th? its in a '96 RD688S

Just skip over 3rd and 7th. :rolleyes:

FW

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This will last about a year or so until one day it gets stuck in either 3rd or 7th. Then you take the shifter out and a long pry bar and pop it out of gear..then you will no longer be able to hit 3rd or 7th. When you drop off the transmission it will cost alot to fix because they will find all kinds of things that need replaced or repaired.

Start shopping for a reman transmission now. Start pricing clutch packs since you will be replacing the transmission and dont want go back in and do a clutch later.

This is a warning sign that is giving you warning now. You can work the truck and make money for awhile, but its going to happen. Yes you can just skip those gears, did that for two weeks while shopping for a reman trans.

Been there and done that...just giving my opinion.

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I had the same problem happen on my MR688S but only 6th gear for me. I took it to mack and they replaced some assembly that the shifter (high / low) attaches to. They told me the assembly teeth was worn out, and it was also popping from high to low while driving. They said it could be from quick shifts where the transmission doesn't go into gear all the way, but you still power through the gear (only partially engaged). After you do this partial engagement for a while (powering the accelerator) it wears a flat spot onto the synchro assembly, and allows the transmission to push out of gear.

Might be similar to what's happening to you.. My synchro assembly was changed at around 400,000 miles (14,000 engine hours)

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This keeps popping up on here if you do a search for 8LL its been discussed. This is a common issue with an 8LL, I have had it done several times, more times than not its in the top end, it will cost about $400 for parts at a reputable shop. I think of the several I have had done once there were synchro/gear issues every other time its been a shifter/fork issue. Go to a reputable shop now and get it fixed if you keep driving it it won't fully engage and youll have to replace 3 gears and synchros and the shifter pieces so the price more than doubles. If you call around most shops have done it and the reputable ones will tell you what i just did the others will say they will have to take it down to know whats wrong.

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That's good information !

I really don't know a whole lot about these trucks beyond the basics, I've only been running with my CDL for 2 years now. When I had my issue popping out of gear we just brought the rig over to mack and they fixed it. They explained to me what they found / did so I tried to relay what they told me.. It ended up being $1200-$1500.00 I believe total.

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From a Dealer not a bad price actually.

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Now that its fixed shift it slow and smooth and don't push it into gear if its right it will drop in, it'll last a lot longer trust me. I shift em with two fingers on the back of the shifter once its ready it'll drop right in, seems most don't like the long gear step to 7th so they force it and then it does what yours did.

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If it's a Fuller, there's a two bit spring in the shifter housing on top of the box that can cause it to pop out of gear if it breaks.

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Well I have a different truck now anyhow. They keep making me give up my normal truck for other trucks, not fun

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When you say pop out do you mean pop the shifter pops out of the gear and into neutral or the actual shifter falls and hits the passenger seat when shifting to 4th? I'm currently working on a 1997 RD600GK (glider kit) with a 350 2v 8LL and 44k bronze camelback dump. It came in for state semi-annual inspection, jake issue, and shifter coming out of Transmisson. I got the Jakes working, minor adj on the the pump micro switch and throttle return spring, inspected it, then tried to get the shifter to come out. I put 25 miles on it before it did it this am. Luckily I was a 1/4 mi from the shop. I got it to do it again in our yard. It feels like the shift from 3rd to 4th skips out and let's the shifter fall into the passenger seat and bounce around. I double and triple clutched it to get it back into a shift pattern. Am I correct to believe it's the shifter, shift forks, or the ball stops in the top cover?

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Yep shifter is wore out possibly the forks, I fixed the same problem in an RD not long ago

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Replaced the shifter late this afternoon. I was told expect it at the shop by noon but didn't get it unitl 4pm lol parts guys....got it put back together and it works good. Thanks for the info.

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We have had this problem on several trucks, and it is usually a simple fix.  There is a brass washer on the gearshifter, I believe on top of the spring. Pull the shifter out, replace the washer, and put it back together.  We have a 94 rd that we have done that to about 4 times and have never had the transmission out of the truck.

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