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Popping out of 5th after LSD install

934 Views 33 Replies 6 Participants Last post by  transzex
I installed an MFactory LSD, a Synchrotech carbon synchro kit as well as various OEM bearings and any items that were not included in the kit in my 93 Si hatch with a D16Z6. I referenced the service manual and several videos. The installation went smooth as well as the first test drive where I went through all the gears keeping it under 50mph. However, on the highway it pops out of 5th between 55 and 65mph. The transmission was not making any noises or grinding and shifted smoothly. I drained the fluid and checked to make sure the snap ring was on the counter shaft bearing which it was. I pulled the transmission again and opened it up and there is no sign of an issue. The car has new Hasport motor mounts, energy suspension bushings on the shift rods and a K-tuned shifter. I’ve had no prior issues with the transmission which has less than 150k miles.
The first thought was that 5th gear may be bad so I am attaching some pictures. To me it looks fine, but maybe there is an expert out there that can verify. At this point I am stumped, the only other thing I can think of is to take it to a tranny shop and have them look for any issue. If anyone knows of anything else I should be checking, I would appreciate their input.

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Have you tried bench shifting the assembly with the outer case off to make sure the 5th gear slider is fully engaging the synchro and gear?

Also, what does the shift fork on 5th look like? If its worn out, it may not be pulling the slider all the way down to the gear.

What about your detent balls? Are all of the detents in place? If you're missing any, the slider could be trying to wiggle its way back to neutral when its running.
Yes, I manually shifted through the gears and 5th looked good. The 93 Si doesn't have dentent balls in the housing like 96's and up. (It's a S20 B000.)
The new slider appears to be fully engaged. I did notice when I removed the main shaft from the shift fork that the 5th gear slider seemed to move a lot easier over the gear than the other gears.
One thing I am confused about is the honda parts shift fork diagram shows springs and balls, #8 and #13 in the diagram. Are these between the shift fork and the shaft where you can't see them?
Right now I have the main shaft disassembled. Once I have everything put back together, I will try everything manually again.

Thanks for your help
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Pics of 5th gear shift fork and with slider
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transez I really appreciate your input. I was hoping you would show mercy and respond. Here are pics of 1rst/2nd forks and mainshaft. If you think the shift forks are acceptable maybe I should put the transmission back in and look for a shifter issue. Thanks
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I disassembled the shift fork assembly - cleaned and lubricated. Took apart the main and countershaft and reassembled. Shifted through the gears before installing. The installation itself went smoothly. Also removed the k-tuned shifter and didn't see any issues. Just took it out for a test drive and it shifted smoothly through the gears, no grinding or whining. Again 5th gear pops out when I hit 50. Since the transmission had zero issues before putting in the Synchrotech carbon synchros, maybe it is the synchros? At his point I give up. I plan on pulling the tranny for the 3rd time (which never gets old) and taking it to a shop and have them go through it. Possibly put the original synchros back in. Worst Mother's Day Ever!
I cleaned and blew out the oil ports and used a minimum amount of sealant when putting case back together to avoid potentially plugging the holes. All the bearings on both shafts are new. The springs and balls in the shift fork looked good. (Verified when the springs flung the balls across the room.) I just drove the car again. It will stay in 5th as long as I stay under 50. Over 50 it pops out and I can't put it back in 5th. I can downshift to 4th and when the speed is lower, I can then put it back into 5th. Staying under 50 with a 350hp d16 is depressing.
No noise or grinding while driving, when it pops it's a hard kick to neutral. All motor mounts are new Hasports. The transmission stopper bracket mount is also new. This time when I installed the transmission, I used an engine hoist and loosened all the mounts. Everything lined up perfectly and was torqued to specs. As stated earlier I dropped the k-tuned shifter to check for any type of obstruction. I even put in a new set of energy suspension shift bushings even though the old ones were less than a year old. There's a couple of transmission shops close by, I think that is my best bet. I don't have the stamina to go through another trial and error event. Thanks

Here's a link to my build: 93 Civic Si Project | Honda D Series Forum (
Out of desperation I took it for another drive thinking that if there was an issue maybe it would cause the transmission to heat up. Outside temp here is in the 80's, took it for a drive. I then used a laser thermometer and took readings at various places on the transmission case. Temps ranged from 134 to 145 so I guess that's ruled out.
I've tried to hold it in gear with a little force only to have it kick out. I haven't tried holding it in with a lot of force because I wasn't sure if I would do damage. I could try it tomorrow.
Thanks everyone for their input.
i don't have anything other than stacking blocks of wood under the lower arm which may be a little risky.
I did put the roller back in the spring. (It was also popping out of 5th before I disassembled the shift fork.) My thought is transmission was fine until I installed new LSD and carbon synchros and synchro sleeve. Now not fine. Could it be those?
I'm located south of Kansas City.
I think it's time to contact a nearby transmission shop and have them check it out.
I agree that a local shop might now be the best choice, but at this point I don't know what my options are. This is my first build and I'm fairly new to the site. From the digging around the site, I know you are the transmission expert and are about 10 hours away, but I don't know if you accept and work on member's transmissions.
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