Shuddering on Launch
 

I am looking for advice on how to proceed. I have a shuddering when launching where gear shift waggles back and forth inside, more exaggerated from a hill stop. Also, seems to get worse once it's warmed up. There are 35K miles on the car, and I think the clutch must be the factory original. So is this a mode of failure for clutches? When I've had worn clutches in the past, it's always been slipping, not shuddering. I'm happy to replace it, just don't want to chase the wrong thing.

I've put a pry bar on the engine and tranny mounts, and while I can deflect them, it takes a good bit of force, they seem okay. Maybe I should try a couple of hockey pucks first?

Thanks!

Here's a video from the underside during a relatively mild occurrence...
https://drive.google.com/file/d/1_Xz...70CKbRe3B/view

Watched your video. Are all your engine/transmission mounts good? Seem to recall you posting in aftermarket mount thread.
. Hockey pucks would restrain engine more but will transmit more of the shudder/vibes to chassis.

Car has 35k but also 30+yrs old. Do you have any history on car from previous owner. I always wonder why some cars have such low mileage. My own car has a story behind low miles on it when i purchased it.
Sometimes people buy cars and just can't get the clutching/shifting thing together and trade for something with automatic or keep the car but just not drive it...much.

The old adage of doubling miles shown on an odometer on a manual trans car certainly applies here. Possible original owner was trying to learn how to drive a manual trans and overheated the clutch from slipping it too much,maybe has some hot spots in pressure plate and or flywheel. Symptoms are akin to warped rotors on brake apply.
Could be broken springs in hub of clutch disc. Possible some oil from rear eccentric seal on clutch disc.Could be grenaded pilot bearing. i'm sure shifter shudders more than what you see drivetrain doing in your video.

IMO removing the trans/clutch to have a look see is in order. The source of this shudder and solution is certain to be found on disassembly. Pay attention to wear on input shaft collar t/o bearing rides on for wear/galling.
I would have a new clutch kit with t/o,pilot bearings on hand and would recommend resurfacing of flywheel and replacing rear eccentric shaft seal on engine while flywheel is off. This will ensure a smooth long lasting clutch job. Did i mention i HATE vibrations,shudders and rattles?

Thanks for the well considered post, GSLSEforme. I am the the 3rd owner. 1st owner had it for 7 years and then sold to his friend who kept it for 20 years on an island on Lake Erie. I bought it from that gentleman, who was a really good guy. He had a number of cars and used this for grocery runs on the island...short trips!

What you say makes sense, while the engine mounts might be iffy (I did go back to the original ones as you noticed in the other thread) that wouldn't be the source of the shudder. Tranny mount is a new one. Honestly the shudder seems *less* severe with the old oem mounts-they are more compact and seem stiffer than the aftermarket ones that were in there.

I am planning to do the clutch job myself, on jack stands in my garage, remove the transmission, not the engine....but it's also my first time doing a clutch. Of course I've read all the threads and I have a pretty good idea of what I'm getting myself into. Just going with a plain vanilla OEM replacement like the Exedy 10025 kit. Key thing is I have all the time in the world!

But the rear eccentric seal was not in the plan, if there is no oil contamination evident, is it necessary? I'll get the part just in case. Any special tools, advice, pitfalls for replacing that? Thanks!

Edit
Reality Check: Is this the part you mean? https://www.atkinsrotary.com/store/6...tegory_id=1004
Thanks again!

Start a new thread when you do this and we can help you out. Might want to invest in a large socket for the flywheel nut (sears used to carry them) and a >300lb impact wrench to get it off.

Will do, thanks t_g. I'll be asking a lot of noob questions.

Trans mount is the likely culprit. It almost always is.

Yes that's the recommended correct part.

The flywheel hub(side toward engine) is also the sealing surface the rear main seal rides on.

You will be putting same flywheel back on in same position but a LOT of times just the remove/install is enough to provoke the 30+ yr old seal to begin to leak. The oil will find its way onto the new clutch disc you just installed.
Result is same as leaky axle seal/wheel cylinder making brakes grabby.prone to premature lockup. If the shudder repair was of an emergency nature(stuck on road trying to get home)and parts and time was a consideration,i'd risk not replacing seal,otherwise for what the seal costs and the time required to replace it=no brainer.

Once trans/clutch removed,you have access to flywheel. It is held to eccentric shaft by a 54 mm (2 1/8") gland nut which has to be removed. Have found some to be really tight but majority can be best removed by a good impact gun(air/electric).

Once broken loose,back the nut off and then put back on several turns(engage threads). The flywheel/eccentric shaft is a tapered friction fit with a keyway,even with nut loose it will not come off. This can be achieved by striking it (on the edge where pressure plate mounts) with a brass,copper or lead hammer 1,2 maybe 3x . You're leaving gland nut partially installed to keep flywheel from popping off and falling on you,using a soft hammer to not ding/mark up flywheel.

Send flywheel out to machine shop for resurfacing. A good shop will charge $75-$100 for this and they WILL remove/replace alignment dowels to do this properly. Ask about this before leaving with them,if they don't/won't go somewhere else. In case you're wondering ,resurfacing is well worth money spent,like resurfacing/replacing rotors results in smoother/longer lasting brake job.

Special tools
- 54 mm socket or 2 1/8" will likely be 3/4" drive and you'll need a 3/4" to 1/2" reducer to use with most impact guns which are 1/2" drive. Tractor supply or a like store has a socket for $12-$15,reducer $3-$4
- Pilot bearing removal tool- important! right tool has the bearing out in 2-3 seconds,everything else leads to headache/heartache,damage to e shaft. Mazdatrix has the tool for sale,Atkins likely also. Pricey,but right tool for the job.
I have and use a blind bearing puller set that has a collet the right size for pilot bearing.

- Pilot bearing/grease seal installation tool. While bearing/seal can be installed with a drift,the special tool seats bearing and seal to correct depth with no guessing. I can send you mine to use and you can mail it back when job completed,have done so with others in club,more than welcome to it. My puller set you could use if local,but shipping would be prohibitive,expensive. You can pm me on this
.
-Clutch disc alignment tool-will come in Exedy kit as will T/o,pilot bearings. One thing i will caution you to do is check the pilot bearing supplied is correct fit on input shaft of transmission before attempting to install in eshaft. Others have driven incorrectly supplied bearing
into eshaft partway where it jams and can't be removed other than cutting it out. Misery and lot of potential for engine damage. Depending on where you source your Exedy kit from,it may or may not come with a pilot bearing grease seal,ask when ordering Still available from Mazda.


Last thing recommended is while trans is drained and out of car,remove t/o bearing support,inspect for wear and replace input shaft seal inside it and the gasket that seals it to bell housing,same for output shaft seal in tailshaft of transmission. Like rear main seal these have a habit of seeping/leaking after being disturbed. Also make sure you check and fill the pocket in shifter tower with lubricant to proper level before reinstalling trans. After all these years likely low or even empty,trans can be tipped over into a container to drain out/clean out what's left in there. This step can improve shift feel.

My recommendations for in/out one time done right job. A little extra time spent on details pays off in long run,makes for a more enjoyable ride. Pm if you have questions

Don't bother changing the pilot bearing if it is still good. Too many people screw this up for no good reason other than they lacked the right tool. Just grease it up and maybe change the pilot seal if it is old cracked and/or leaky.

This is great, thanks for all those pro tips. This last one is the best ^^^^

Welcome. While you have driveshaft out,check u joints over good feeling for sloppiness or tightness/binding.

But it's new!!! ;)

Seriously though, it is an OEM grrade one from RA, probably not the the stiffest. I can deflect the tranny sideways a bit with a pry bar, but it takes real effort.

Wait, what year is your car? The 84-85 trans crossmember has some rubber with steel inserts that can separate and fail.

Should have stated all the facts...it's an 83 GSL 12A with 35K, stock Nikki, stock exhaust. Actually only real upgrades are RB springs and Tokico Blues, nothing on the power train.

^^^^ Spooky man, just spooky.

Here's my tranny mount as installed, as I discovered this evening. Gonna replace (with one that has 2 nuts AND 2 bolts) and test drive.

https://cimg1.ibsrv.net/gimg/www.rx7...8a7a7df03b.jpg

From reading your other thread just now, I see what you are talking about, and I have discovered similar problems in my travels. Yes, a stud is a good idea for you as this will be a sturdier option, especially in a hole that may have been wallowed out by a loose bolt before it worked its way out.

The hardware size you want is 8mm x 1.25

It looks like the correct mount, and once he gets it out to inspect the threaded holes for damage, he will see that there is either a slotted hole or two sets of holes in the mount. Also a stamped RH which I think is supposed to mean "right hand" to indicate installation direction, but I don't recall which direction RH is supposed to be pointing. They are definitely directional.

Thanks you guys. Haven't yet inspected the trans case yet.

There's a guy selling a competition mount, PM'd about getting it.

+1, I was going to mention that as well. The last mount I used from RA had 2 holes and I just needed to line up the right ones and get the direction right. The direction is determine by the built in tilt the mount provides for the rear of the tranny. It will; make sense when you go to put it back in.

GLSSEforme, Jeff20B, t-g, I'm a fool with a wrench!

It is indeed the mount from RockAuto with an extra hole. And the installer did a fine job lashing it up. I just couldn't see the bolt that was always there, properly installed, and jumped to conclusions.

https://cimg4.ibsrv.net/gimg/www.rx7...c67575c39e.jpg

All this got me poking around and the cross member isolators on mine are toast. I saw a post somewhere about solid mounts, since the bushings are NLA, any real downside to solid. I'm assuming more vibration transfer to the chassis, but these cars aren't known for comfort and quiet.

To put some resolution on this, I ended replacing the clutch, throwout, pilot bearing, transmission seals, engine rear seal, clutch master and slave cylinders. The crucial part was the new clutch and resurfacing the flywheel. While the slave cylinder was leaking, it was only noticeable on reassembly/inspection and hadn't failed completely yet.

Anyway, comprehensive post and details on the clutch job is here: https://www.rx7club.com/1st-generation-specific-1979-1985-18/first-time-clutch-more-replacement-thread-1128545/

Thanks everyone.