nater

about a week ago i pulled out of parking lot that was a weird angle and the car bottomed out pretty bad. then right after that my speedo was jumping between 0 and about 35. at the next stoplight i turned the ignition off then back on and the problem went away for the rest of the day. then the next day it started acting up again and the off/on trick didnt work. then it seemed to only have done it when the car was warmed up. i took it easy on the car and didnt drive it much. this weekend i had to drive it quite a bit and the problem got progressively worse. it started out with minor glitches then it move to only reading something other than 0 when i wasnt accelerating or if i hit a bump just right. then it would stop altogether. then it worked fine for 30 some miles and i passed someone and it quit again. i just drove it today with a volt meter hooked up and the voltmeter would read steady increasing with speed up to 1.2 some ac volts but the speedo read 0 if i hit the brakes with moderate pressure the voltage jumps up between 3 and 5 ac volts depending on speed and my speedo works until i come to a complete stop or accelerate again. i know the problem isnt the dash and the voltage changes seem to rule out the speed buffer but i dont know if its my vss or the wiring to it. also while i was working on it i crawled under to inspect the wiring i didnt find any obvious problems but most of it was in a loom and a tight space, but i did find that my transmission mount is broken again. i have also noticed a little more wheel hop taking off hard in drive and really bad hop in reverse at anything above idle. my question is my speedo problem more likely the sensor or the wiring and would my broken tranny mount have anything to do with it?

henryd3

iTrader: (128)

Your broken mount has a lot to do with your problems. Don't really know how your car is or should be wired, but it sounds like loose connections that suffer from being moved around a lot. Your torque arm is braced on the trans, and since it is not solid translates to your rear axle moving around and causing your issues. Fix the trans mount ASAP And take it easy in the meantime

John in RI

iTrader: (167)

I gotta' wonder if the plastic "neck" of the VSS is cracked/busted. It's pretty tight under there and damage to the tranny mount could easily have allowed the tranny to move around rather than firmly held in place - leading to a damaged VSS.

Your description also sounds like it could be worn plastic speedo gears too.

I'd replace the Transmission mount ASAP and while your under there I'd check the VSS REAL close for any cracks/damage. I've seen the outer metal trim/crimp that holds those things together break simply due to age,..... additional "stress" can help their longevity. You could try to remove it to inspect the plastic speedo gears,... just be REALLY careful 'cause those 84-88 VSS's are getting hard to come by !

nater

when i was under the car i didnt see any cracks on the vss, but that doesnt necessarily mean anything. hopefully the worst case scenario is the speedo gear, although i dont know what to replace it with. this is also the second trany mount ive broken in a year and a half and for a "bone stock 305" like the previous owner said it pulls pretty damn strong, so im not sure that the rear end is stock or much else of the car for that matter. is there any chance the vss from a different vehicle could work or be modified to work? could my problem just be the transmission moving around because of the broken mount? could trany fluid level have anything to do with it, its about a half quart high but leaks often? slightly out of context on this board but should i go with a high performance trany mount like energy suspension, since i have broken two autozone replacements now? my transmission cross member bolts are also stripping so im gonna fix that while im at it, what is the best way to make it easy to remove the cross member if my problem isnt solved?

John in RI

iTrader: (167)

OUCH !!!

Dude - don't touch ANYTHING under there until you get the cross-member FULLY secured under the car. Stripped cross-member bolt holes is a REAL BAD THING and that needs to get fixed ASAP. If you make any attempt to remove the cross-member bolts and strip them any more in the process,... you might not be able to re-install them and if you can only install them 'half-assed',....... than your whole drive-train could fall out from under the car.

FYI: I've got good factory Tranny mounts, blasted, painted and ready to install @ $15 + shipping.

The fact that your cross-member bolts are stripped is almost certainly why the tranny mount has been a repeated problem for you. Don't screw around - get those cross-member bolt holes fixed ------> RIGHT AWAY !!!

P.S. the only other cars ( that I know of ) that used the same VSS as the Berlinetta is the 86-89 Firebirds and in the Corvette for a few years in the mid-eighties.

nater

ya those cross member bolts were a real bitch the lat time it replaced the mount and ive just been putting it off for a while they hold for now but im sure if i remove the cross member again they wont. problem is they are stripped the worst possible way, the welded in nut seems to be cracked as we tried drilling and tapping one and that bolt just pulled though the new treads. what i dont know is how to fix it. i dont want to cut the floor or the frame rail. there is still enough threads there to get a bolt to stay but i cant torque anything down. would it be possible i could screw in a stud to the whole and then weld it in place? also if my speedo gear is bad ware do i look for a new one? another question doesnt the vss output 2000ppm for the 84 berlinetta, in theory could i just use whatever vss i can find that fits the 700r4 and outputs 2000ppm, maybe thats the wrong number but still same concept matching output and make sure it fits the tranny? or is the elecrtical part more complex than that? could my problem also just be the large amount of movement the tranny is doing because of the broken mounts? i ask because i dont realy have a good way to test the vss since its intermittent and would hate to go through fixing the mount and cross member just to find out id have to shell out a lot of money for a very specific vss and redo everything. id also hate to shell out the money on new parts that dont need replaced just to find out its a wire shorting when the tranny moves. i just want to know where i should be looking, it seems like its always the stupid easy solution and want to cover that first.

John in RI

iTrader: (167)

Yes, your intermittent speedo readings COULD be simply due to the tranny movement. ( Could still be MANY things as nothing has been ruled out yet. ) Yes; The Berlinetta VSS is a 2000PPM unit. The only cars with a matching electric VSS are those I already mentioned, 86-89 Firebird and about the same year Vets. ( Are there others - Maybe !?!? )

I've seen people "fix" stripped cross-member mounting holes several different ways, some better then others ! However you decide to fix them - DO IT RIGHT AWAY ! With the tranny moving around it will not take long for those ( already bad ) holes to fail completely. We can already see the snowball effect of letting a problem linger,.... ( bad mount makes bad holes, Bad holes lead to another failed mount, now speedo problems ? )

I wouldn't worry about the Speedo reading - get it out of your mind completely cause you've got MUCH worse problems to deal with.

If you don't want to destroy your car than get that X-member mounted securely RIGHT AWAY. While making that repair you can also replace the dead tranny mount ( CHEAP ) and you can also closely inspect all the speedo related parts in that area.


Fix that X-Member !!!

nater

ok so got the cross member fixed and a new mount. i then spent a lot of time testing the vss and running new wiring to it. got the wiring ran to the point where i needed to splice into the old wiring and found the problem. the connector for the vss was bad i couldnt get it apart to see just what about it was bad, but the was no continuity between the connector leads and the wire just 6" behind it. luckily it is the same connector as part of the smog system harness so it didnt take too long to get my speedo reading after that.

John in RI

iTrader: (167)

VERY COOL ! Sounds like you had a very productive weekend, Those repairs were real important and it's good to know that you're tranny will not be falling out from under your ride any time soon ! Add that to a fully functioning Speedo again and your car should be much more enjoyable this summer.

nater

yes it is much more enjoyable, and thanks for your help. i might do a write up soon on how i fixed the cross member i just need to get the packaging for them so i can give the exact size carriage bolts i used. i think the only thing better than having every thing fixed is the fact that it was free(trany mount was under warranty) minus my time, and didnt take nearly as long as i thought.