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Popping out of 5th after LSD install

1158 Views 34 Replies 6 Participants Last post by  rgm_93si
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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I highly suggest having a buddy get into the car while you are underneath (jacked up and supported, of course) and look closely at the bottom of the shifter when you get 5th gear engaged.

It is too easy to have something slightly off.

Being these are bar shifter cars, you can have perfect everything except one gear being a bitch.

If the engine moutns are new, loosen all the bolts holding them (ALL of them), fire the engine up, rev it a few times to get it to move, and while idling, tighten as many botls as you can reach without danger of dropping a tool somewhere where sparks or moving shit might be.
detent springs? condition, age, etc..
I am assuming, no noises? no grinding, either by noise or by feel?

When it pops out, does it behave like it lost tension and kicks to nuetral, or does it feel like it "socketed" itself out (initial resistance)

I ask, because Im trying to figure out in my head if there is anything at say, 45mph, or 48mph, that slowly climbs up, then pops.

Is your exhaust extremely bass sounding? Maybe there is a perfect pitch that does something.

Im spit balling here

One thing I might try in your shoes, if EVERYTHING looks and feels good, is to loosen each and every one of your mounts and associated bolts/nuts. Just enough to let it move or rock around. Then have someone while it is idling, engage 5th several times in and out while you look under the hood.

Even if it only happens at speed, I wonder if the shift linkage is doing something. Maybe a big burr in the shifter ball?
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That description of a hard kick to nuetral is something Bone might have a trick up his sleeve for, or at least something to look into.
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.
Do you have a safe way of getting the car into the air, supporting the control arms so the axles are close to ride height, and running the car in gear?

Dont let the suspen sion hang. It puts stress on the axle seals from the joints hanging low, and can create a leak. No real point in making a reason to change the axle seals, especially since 95% of the aftermarket doesnt understand quality control

EDIT I have seen people use a threaded stud in place of one of the half arm's bolts, and use that as a support brace. Just be super careful to not have anything touch the tire of course!!
Wheels removed should in theory give enough room to brace the control arms. But if you think even a tiny bit it might not be enough, dont do it!
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