850 clutch judder - trans tunnel plate/gasket replacement

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850 clutch judder - trans tunnel plate/gasket replacement

Postby Bob » Sun Apr 26, 2009 1:08 pm

I was experiencing bad clutch judder in my '72 Fiat 850. Every time I would identify something wrong and fix it, it seemed to help a bit, but then would get worse soon after. I put in a new clutch assembly and had the flywheel dressed a couple years ago. I replaced the motor/trans mount rubbers, re-welded the later-broken trans mount brackets. Put in a new clutch cable and replaced one of the actuation rods under the dashboard from the pedal assembly. All to no avail!

Yesterday (the weather got much better), I crawled under again and inspected the plate through which all the cables, rods and tubes route through the rear of the transmission tunnel to where they connect with the engine/trans. Here, there is a bracket welded to the tunnel that holds a rubber-covered steel plate that has holes for all the tubes and cables exiting the tunnel. The sheath around the clutch cable is held at it's front end by this plate. I believe I've found the trouble. About half of the bracket holding this rubber-covered plate had broken off of the chassis completely. Fortunately, I was able to recover all the bits and welded them together and welded it back to the rear of the tunnel where it goes.

The next problem is the rubber/steel plate. Mine is all steel at this point with only vestiges of the original rubber remaining. I've ordered a new replacement from Argentina off eBay and will wait to re-assemble the whole thing until it arrives.

Here's the question: does anyone have a photo of how all the cables, tubes and rods are supposed to go through the holes in this plate? I can't believe for example, that one should be required to remove the hydraulic brake line to the rear brakes to fit that tube through one of these holes (but then Fiat is known for wonderous and mysterious engineering). Let's see: there is the hydraulic tube to the rear brake splitter, a wiring harness to the engine bay, the two tubes for the heater, clutch cable, choke cable, accelerator cable, emergency brake rod, shift rod and three holes for the screws that mount the plate to the bracket.

Does anyone have a photo or diagram? I looked in my Fiat factory shop manual- nothing. The Haynes manual only has a repeat of the factory photos. I'm convinced that someone has monkied with this plate in the past and probably gotten some of the cables, etc. in the wrong holes. Anyone out there have an un-molested 850 with the engine/trans removed that could take a quick photo?

Thanks in advance!

-Bob
Bob
 

Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby noah1 » Sat Aug 16, 2014 10:46 pm

sorry you didnt get any help or even a reply.
I bet you figured it out by now.

i have a similar problem.
i got an 850 spyder and most of it was in boxes.
the clutch cable was still attached but doesnt look right.
it bucks severely in first and is smooth as silk in reverse.
i never let the clutch out all the way in first because it bucks so bad i thought it would fling the engine out.

did you figure out yours?
did you get any pics?
routing diagram?
end mounts for outer sheath pics?


any help would be greatly appreciated.
i cant find anything on the information super highway.(the web has a big blind spot for 850's)
i feel like i have a computer virus that blocks most of the useful info about fiat 850's.
thanks in advance...0 degrees or 10 i still dont know (850 joke)
thanks
kevin/california
noah1
 
Posts: 5
Joined: Sat Jul 05, 2014 4:38 pm

Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby Bob » Wed Aug 20, 2014 12:01 pm

Kevin,

Yes, I finally did get the problem solved. As mentioned in my post earlier, I tried all kinds of things and in the end, found that the bracket where the cable shield mounts was broken off. The shield is a rubber-coated metal plate with a number of holes in it. It's mounted at the very rear of the transmission tunnel and is where the key cables and rods go through. I believe its purpose is twofold. First, the rubber covering acts as a gasket to prevent dirt/rodents/etc. from getting into the tunnel. Second, it acts as a steady plate that holds the end of the cables in place. Specifically, the clutch cable depends on this plate to stabilize the end. Without it, the clutch cable has no place to brace against the pressure from the clutch mechanism and will therefore judder 'til the cows come home. This was exactly what was happening to mine. I went under the car with my MIG welder, pulled out the original gasket/plate and welded the mounting brackets back in where they were supposed to be. The brackets are simple little L-shaped sheet steel things spot-welded to the sides of the tunnel. I had a beast of a time getting them welded back in and in hindsight, I think I should have drilled holes in the sides of the tunnel and plug-welded them back instead of trying to do it from the inside of the tunnel as I did. I got it all right, but it involved lots of language that would have embarrassed even Mark Twain himself! Not pretty either, but hey, if I couldn't see it to do a good job, nobody else will. Today, it's been fixed for many years with no problems. As soon as I put in the new gasket/shield (got brand-new from Argentina via an eBay seller called "hecgre"), the problem disappeared! Since I'd failed to take note of or photograph the routing of the cables/shafts through the plate, I made my best guess and it worked out fine.

Hope that helps. If you need, I can get under mine and take a photo of the cable routing and post although I can't guarantee it's the original configuration. Let me know.
Bob
 

Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby noah1 » Sat Sep 13, 2014 2:30 pm

Thank you for the reply.
i have been building my 850 spyder from boxes of parts.
it is a lot tougher than i thought it would be.
lots of intricate details are not in my book.
do you know if the clutch cables outer shield has clips or something to hold it to the stabilizer mounts?
also ,timing is still a mystery.
the engine compartment says 0 degrees.
the book says 10 degrees.
what do you set yours at?
thanks
kevin
noah1
 
Posts: 5
Joined: Sat Jul 05, 2014 4:38 pm

Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby Bob » Thu Dec 04, 2014 2:11 pm

Kevin,

No, There are no clips that hold the end of the clutch cable sheath to the stabilizer. As I recall, the end of the clutch cable sheath has a machined boss on the end that goes into a corresponding hole in the plate. That's all that's needed as the cable sheath is then captured between both ends.

Regarding the timing on the engine - it's been a mystery to me too and I've heard from others that they can't get the timing right by using the marks as outlined in either the factory or aftermarket manuals. The owners manual and the Fiat factory manuals say "Basic ignition timing - 0 degrees (TDC)" which means timing should be set at top dead center. Also, the factory manual (and the aftermarket manuals) have a supplemental section in the back of the book specifically for the later models (like my 72 sport spider). They have additional instructions, but aren't much different than the regular 850 instructions. They've never worked for me. I have a Haynes manual too which goes into a bit more detail on how to set the timing. They recommend 10-11 degrees BTDC depending on the model of engine. Of course, the difference in one degree is impossible to measure accurately on ANY car let alone these 850s. But, even in the Haynes manual, they recommend setting the timing and then running the car to see what the results are and making adjustments. And that's exactly what I have done. I first ensure the points are gapped accurately and then set the timing to around 10 degrees static timing. That means putting the timing mark on the centrifugal filter about 1/2 to 9/16 inch to the right of the timing mark on the timing gear cover. Remember, these engines run counter-clockwise, so that would represent Before Top Dead Center (BTDC). Then, I usually start it up and adjust the idle speed to about 850-900 rpm and check the dwell with my meter (should be between 57-63 degrees) and adjust as needed - tiny adjustments make big changes in dwell so I always check this by meter rather than relying on point gap. Once that's set, then I run the car on the road and see how it accelerates and whether I hear any odd noises. If I can wring it out at high rpms and still have "power," then that's a good indicator. Also, if the timing is off, I've found that the starter will barely turn it over until I adjust. Once I have it running good and the dwell angle remains good, I clamp down the distributor and call it good. :shift: If I check with a timing light, it's never right where it should be - 0 degrees? 10 degrees? 34-1/2 degrees? Something else? :bang:
Bob
 

Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby noah1 » Thu Dec 04, 2014 5:41 pm

Thanks for the reply.
most judder went away when i wired the cable sheath to the rear mount/guide.i have yet to see the front sheath mount/guide in the tunnel.i also found that the torque transfer rod from the pedal to the pull arm in the tunnel needed a new insert/sleeve/bearing.as soon as i get it painted i'll put in a new cable i just got and do it right.
my fiat finally runs and drives.i have it stripped and primered and ready for paint now but the weather is bad and it is real humid and cold where im at.
timing...im going to do like when i was young and cars were cheap and do the timing by turning the distrib till the valves ping at full throttle under load,then back off till no ping.
i will check the degrees when done for future reference.
i sure wish fiat would make 850 spiders again.
when im finished with that fiat i can start in on fixing my other one.it is in way better shape.
my nephew thinks i dont need 2 and should give him one....haha...the silly kid.
he has a few girlfriends...hmmm....maybe he should give me one??? lol
Thanks again.
Happy Holidays,
kevin
noah1
 
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Re: 850 clutch judder - trans tunnel plate/gasket replacemen

Postby Bob » Thu Dec 04, 2014 6:09 pm

Kevin,

Sounds like the right way to go on tuning these little beasts. I'm sure you'll get it just right.

Good luck on sorting the clutch judder and getting all the bits back together. If there's anything I can do to help, just let me know.

I'm surprised your nephew wants an 850 - I offered to GIVE my 850 to both of my kids when they came of age and they each declined! I suppose it had something to do with my constantly working on it, the seemingly un-solvable clutch judder and other problems that I had only recently resolved from the work done by previous owners. Since it didn't seem like a totally reliable, turn-key and drive sort of car, they weren't so interested. Man, if I'D been offered a spider when I was 16, I'd have fought someone for the chance! :lol: So, it's actually really good to know there are young people with an interest in these older classic cars and that they might just not die off as our generation does.
Image

Happy Holidays!

-Bob
Bob
 


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