6 speed shifting issues
Thread Starter
8th Gear
Joined: Aug 2011
Posts: 8
Likes: 0
From: Grapevine tx
6 speed shifting issues
I just bought a '96 LT4 with a 6 speed trans, love the car, but I have issues (sometimes) while shifting. It seems really notchy from 2nd to 3rd, and it's even hung up in the gate a couple of times. I think it may have a broken trans mount, but I only feel it under high power in first gear. When it's cold and driven fairly gently, it seems ok. Does this trans have external linkage? It feel like the problem is there.... Thanks!
Racer
Joined: Jan 2007
Posts: 380
Likes: 1
From: Toronto Ontario
I have the same car and no issues. How many miles on the car? Is it possible that a previous owner installed a short throw shifter incorrectly? Is the rubber boot underneath in good shape properly secured? Is getting into reverse a problem?
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I just bought a '96 LT4 with a 6 speed trans, love the car, but I have issues (sometimes) while shifting. It seems really notchy from 2nd to 3rd, and it's even hung up in the gate a couple of times. I think it may have a broken trans mount, but I only feel it under high power in first gear. When it's cold and driven fairly gently, it seems ok. Does this trans have external linkage? It feel like the problem is there.... Thanks!
I absolutely 100% guarantee the ZFDoc specialist would recommend to verify proper operation of your clutch hydraulics first. Check the level. Recheck after a reasonably short period of time.
If that proves O.K., he would recommend you give the car time to wear into your shifting technique/pressure. According to him, 10k miles should allow some conformation to your style.
This problem is often reported about ZFs. Way more often with black tag (earlier models though).
Don't panic. BTW. Unplug CAGS as mentioned. It shouldn't affect your 2nd to 3rd shift but just in case....it's easy to do.
Race Director
Joined: Feb 2003
Posts: 11,671
Likes: 20
From: Lake Wylie SC
I found that you really have to fully press in the clutch while shifting. If this doesn't work, I'd do a fluid change and try it again. The PO should be able to give you some info on how he drove it, ie, drag racer, auto cross or HP. If the clutch is wearing shifting becomes notchy.
Drifting
Joined: Aug 2009
Posts: 1,968
Likes: 242
Well good news for you here, we don't have a trans mount. Trans bolts up to the bellhousing and the C beam connects the tailshaft of the trans to the rear differential.
Check that the C beam bolts are not loose. There are 2 that go through the rear of the trans and 2 that go through the differential. If they get loose they can cause vibration, noise, etc and wallow out the holes in the aluminum C beam.
and +1 for new fluid in the Trans. I have Pennzoil synchromesh in mine right now and get an occasional notchyness going into 3rd. I have Amsoil sitting on the shelf waiting to go in when I have time.
Check that the C beam bolts are not loose. There are 2 that go through the rear of the trans and 2 that go through the differential. If they get loose they can cause vibration, noise, etc and wallow out the holes in the aluminum C beam.
and +1 for new fluid in the Trans. I have Pennzoil synchromesh in mine right now and get an occasional notchyness going into 3rd. I have Amsoil sitting on the shelf waiting to go in when I have time.
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Race Director
Joined: Feb 2003
Posts: 11,671
Likes: 20
From: Lake Wylie SC
Over the years we have had indepth discussions about what to use in the ZF6 tranny. Most say to stay with GM recommended fluid or Castrol's fluid that you get from a BMW dealer. I stayed with GM's oil and it's been good for 30K so far. Do a search and you should find lots of info.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
I have occasional problems getting mine into 3 or 4 at slow speeds on the street and shifting like grandma. I just push the clutch back in put it in neutral and try it again. Usually works the second time. What is funny is that if I shift faster or at a higher RPM I do not have this problem at all. In fact it shifts like butter under WOT conditions and shifting like you mean it. I run Redline Lightweight Shock Proof Gear Oil, it is Smurf Blue to be easy to spot. No complaints. Black Label ZF, FYI. Noisy, little SOB, but I kinda of like it. Sounds kinda like an old school M22 Rock Crusher.
