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Discussion Starter #1
My sport comp 160 MPH speedo has some issues.
It seems to work well when cruizin or going slow, but when I accelerate, It actually indicates I am slowing down then, when I let off Or reach a steady speed, it will "catch up".
I suspect the cable is getting wound up but can't imagine why or why it didn't shorten and pullout

Super t-10 tranny. The fairly new cable doesn't have any sharp bends. It leaves the tranny on the PS, come in threw the firewall where the heater wire is and goes across the dash into the speedo angle mount.

I will look carefully at the input 90 deg elbow, maybe it can be lubed?
 

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I'm pretty sure a stock speedo cable can be lubed. You disconnect the speedo cable from the speedometer and pull the wire portion of the cable out from the sleeve... then lube the entire wire cable with some wheel bearing grease and reinstall back into the sleeve (that's how I lubed mine).

You may also want to check the speedometer gear within your trans that connects to the speedo cable. The speedo cable connector section of this gear should match the end of the speedo cable (square peg into square hole). If the gear is made of plastic, it is possible that the cable connector section is rounded and slipping as you accelerate (cable is under torque)... but as you cruise, the cable is under less torque so it is able to stay connected to the speedo gear within the trans. If possible, you may also want to check the speedo cable connection piece within the speedometer for any signs of wear.

You may also want to inspect both the drive and the driven speedo gears within the trans for any signs of wear (as worn gears may also cause this issue).
 

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Discussion Starter #3
Thanks Rif.

I was thinking the same thing about the plastic gear...I can't remember if I ensured the fit of the cable into the gear the last time I replaced the tranny, which means I probably did not. maybe its as simple as replacing the gear.
thst would be nice, something straightforward and simple to fix...LOL.
 

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Discussion Starter #4
The cable spins freely when disconnected, I didn't have a helper to watch the speedo while I hooked a drill to it... the gear is definatly worn, the teeth are chewed a bit, and the spiral stem is rough as well. I think it is binding in the adapter , as it is rough inside as well. I tried smoothing it out some but I think its 46 years old. I also think the assembly is moving away from the drive gear in the housing as its a bit sloppy. The O-ring is not a standard size that I have in my kits.......The blue speedo drive gear in the tranny is fine (fairly new T-10)
AS I don't know if this is the correct gear to begin with, I ordered a compete kit on e bay, a new adapter, the rainbow of colors of gears etc. rather than just replacing the gear.
Thanks Rif, and I will pull the cable and slop grease all over it...
 

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That speedo gear definitely looks worn.
I'm curious what the speedo cable input hole looks like on this speedo gear (located at the end of the spiral shaft). Is the cable input hole still a square shape?... or does it look rounded out?
 

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Discussion Starter #6
Its fine just a bit open at the tip, probably made that way to help, uh, guide the insertion of the male part of the cable. . the cable slides in pretty tight and to the correct length. I tried to get a pic of the hole but no joy. that's probably why I forgot to mention it. I took some dimensional readings as best I could, to make sure the cable was long enough, wasn't slipping out, not to long..etc. I also checked to see how far the gear and adapter went in the hole. Depth seemed fine but it seemed bit sloppy. I bent the retainer piece to hold the adapter in deeper. The new stuff should be here Friday, If the car is still drivable ( have alt of stuff planned) by then Ill see how it goes, and have my friend run next to me at 60 mph and see if the brown gear is correct.
 

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Discussion Starter #10 (Edited)
you can check that speedo speed with one of those hand held GPS's.
Thanks for your post I did load an APP and it did work. Unfortunately the speedo is still not 100%. It no longer slows down( indicated) when I am accelerating, but, E.G. at 60 MPH steady I accelerate. the APP says 85 MPH, the Speedo still indicates 60. Then, after I let off the speedo "catches up".
The new Billet drive adapter went in tight and securely with the new lock bracket and bolt. the cable went into the adapter housing and new gear drive easily. The 20.00 kit came with all the colored gears and spare O-rings ..... I'm irritated.. I was optimistic.
I was short on time so did not pull the cable and grease it, nor did I lube the drive gear shaft with gear oil.
SO I will have the wife help me watch the speedo while I drill the cable, then pull it, check the end at the speedo, then grease it, although the grease Is more for preservation than lube. after I put the cable back in the speedo Ill check it again with a drill . Then Ill pull the adapter and check the gear for binding. It was tight in the adapter....

I ordered two more brown gears from rock auto..... JIC.

Pics of the kit etc...

*** notice the New gear is about 1/4" longer than the old one... It didn't not appear to be an issue. bit Ill check it against the ones coming rom rock auto
 

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Discussion Starter #11
Last night I was able to pull the speedo cable out from under the car and use my cordless drill to check the speedometer cable.
I lowered the car on the lift enough so I could stand up and look in at the speedo with the door open. I couldn't see very well, but once I figured out the drill has to go in reverse I could see the needle moving. luckily my neighbor came over and watched the speedo while I modulated the speed and actually pushed and pulled on the cable some. The speedometer responded toll inputs immediately and showed steady speed , from 20 mph to 100. I could not pull the cable and grease it, it doesn't come out unless you disconnect the cable form the speedo. There is a lube point in the 90 deg output adapter in the back of the speedometer, so today the PO and are going to pull the gauge panel, fix some lighting issues and make sure the cable is tight a and lube it.
I'm so baffled by this I even wondered if the if the blue drive gear in the tranny could be slipping.... Attached shows that is unlikely.
 

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It's always easier to suggest something than to actually do it but you're desperate so here goes:

Try this - Install your speedo cable to your adaptor, then insert your driven gear into the adaptor. Now try the drill on the end of the driven gear and see how your speedo needle reacts. Why?
I had a speedo needle that was dropping-out (slightly different problem, I know) but found the driven gear being spun isolated the transmission drive gear out of the problem and saved me a ton of wasted time and energy.
My problem was resolved with a second brand new adaptor from Auto Meter. Who would guess a brand new part would be defective, eh? :no:
Tim
 

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Discussion Starter #13 (Edited)
It's always easier to suggest something than to actually do it but you're desperate so here goes:

Try this - Install your speedo cable to your adaptor, then insert your driven gear into the adaptor. Now try the drill on the end of the driven gear and see how your speedo needle reacts. Why?
I had a speedo needle that was dropping-out (slightly different problem, I know) but found the driven gear being spun isolated the transmission drive gear out of the problem and saved me a ton of wasted time and energy.
My problem was resolved with a second brand new adaptor from Auto Meter. Who would guess a brand new part would be defective, eh? :no:
Tim
Wow thanks, and that is the next logical step, and I can do it without driving the car, which is good cause I removed the Distributer last night.
took the dash out last night and fixed the lighting issue by putting all the same bulbs in all the ( sport comp) gauges, fixing some bad connections. While it was out we greased the cable at the zerc and checked the tightness of the 90 deg adapter and cable. went for a test drive and it seemed to be the same, maybe bit more responsive.
Good news is the dash lights up evenly and that includes the heater controls. very happy about that. We changed the hodge podge of bulbs, 161, 169, and a few 194 to all 194 and removed all the green lenses... nice and bright and the dimmer works flawlessly... (new light switch also.)

I'm going to try and make the routing of the cable a bit better, I think I may be able to lessen a few of the angles , although they don't appear to be too sharp now. I'm also looking into a new cable as they are not expensive, but the ones I see sofar don't appear to have the correct fitting to go into the speedometer.
 

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Discussion Starter #14 (Edited)
yesterday I pulled the new adapter and used my drill on the gear. even as I pulled out the gear over 1/2' the speedo responded. I looked up in the hole in the tranny and can see where the gear tip rides on a machined boss.
I think this may be the problem. Perhaps the gear is being pushed into the area and binding as the car accelerates. I would think the teeth would be chewed up already if they are jumping off of the blue gear but maybe not. I measured and compared the depth of the adapter w/ gear s best I could.....inconclusive. I can't see very well with the cross member etc. in the way. But I can cram my phone in there a bunch of times and get some pictures.

When pull the tranny I will be able to hopefully smooth out that area. It does not feel overly rough with my finger.

As an experiment I put the old adapter back in with new o-ring and gear....It was raining out, so no test drive... then I pulled the headers...

Pictures are of the inside of the tranny through the speedometer adapter hole.

maybe someone can look in their housing and tell me what they have. reminder this is a T-10- 4 speed.
 

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Discussion Starter #15
Today I called Richmond gear... they " never heard of that problem" but agreed to check the specs and get back to me, perhaps there is a depth measurement I can take. I never heard of this either, but everything else checks out. the speedo works when I drive the driven gear with a drill motor perfectly. I'm convinced this is a casting issue, or part of the boss/ nub up in the tranny fell off, allowing the driven gear to ride up in the hole and off of the drive gear (big blue one), causing the speedo not to work. I don't expect much in the way of compensation..... the tranny is 4 years old. I would like them just confirm what I am thinking so I can justify spending 200 bucks for a new tail shaft. also will need a new bushing. Well, maybe they send e some discounted parts.... Tranny is coming out, I broke a tooth off of 1st gear and it grinds going into third/ and or pops out... this will be the second rebuild in less than 1,000 miles. NO I didn't beat on it.. not much... I did have some wheel hop a few times....that explains 1st ,but they missed something in the rebuild IRT third. Maybe , maybe Ill attempt repair myself...
 

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Hi Rupert
Here goes - - I'm not too sure on u'r speedo . . . . . but, when I changed from my P/G to my T 5 , I wanted my stock speedo to work .
the T 5 trans has / was VSS speedo (electric drive) to stock speedo (mech. drive in my dash). O K .
I used a phone app

Ruppert - the phone app should help - - - after you get back together , and , too check / compare your speedo , for readings.
once you choose the tranny gears. Your phone would / should pick-up the satellites readings . . . too compare your speedo gears . . . .
Your phone will read how fast you (your phone) are going . . .. then, look at your dash speedo . . . . compare.
Check the mile markers for your odometer miles .

wouldn't this work for your speedo readings . . . . jim
 

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Discussion Starter #17
Thanks
I just remembered that I did use the phone app, I think I tried to post during the sites swap over with neg results and gave up. IN fact I used the app to se how fast we were flying when we flew in from Canada a couple weeks ago.
The problem is:
Upon acceleration the speedometer doesn't move. The app verified I was doing say 90 and the speedo was at 60, which was the speed I started the WOT run from. I didn't need the APP to verify the issue, but it did help show how far off it gets to. Once I let off the gas, the speedometer, "catches up". Anytime I do anything other than a slow increase in speed the speedo lags like this.

When I use a drill on the driven gear the speedo responds perfectly to all changes in speed.
The only thing left this could possibly be it a problem between the driven and drive gear, perhaps the housing was drilled wrong, allowing the gear to walk up and away form the drive gear.
 

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I modify transmissions adding a cable speedometer drive to them and I'm constantly calculating what speedometer gears are needed for customer cars. I can do the math, but I use TCI online speedometer gear calculator. Quicker and it's accurate.

You type in your metric tire size and it tells you the diameter, then go up on the page and put the tire diameter, axle ratio, and number of teeth on the drive gear and it tells you what gears you need.

Thought this might help.


 

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Discussion Starter #19
Thanks, I have the correct gear. when cruizin the speed matches the APP. upon acceleration the speedometer does not respond. I believe the gear is walking up into the tail housing and loosing contact with the drive gear.I'm looking for solution. Richmond gear has not responded as they promsed to
 

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From what I can see the older original T10 drive gears (and others) are different from what I use in my conversions. I use T5 drive gears.

The T10 transmissions and some older GM transmissions had a longer "bullet". The round housing shaped like a bullet and used a longer driven gear. (See pic) The turbo 350 ones are the shorter gear and bullet.

You can use turbo 350 bullets with a turbo 350 gear. They work perfectly. The T5 style gears and bullets are not available anymore.

It doesn't look like that's the case with your parts, but here is a pic showing the difference between bullets and gears just in case.

I grabbed a T5 housing that has a cable drive from the factory and measured the depth of the hole for the driven gear, It's 1.700 or so. I have seen a few (but far between) ones that the driven gear binds when you put the gear and bullet in and tighten the hold down. On those I just sand down the end of the driven gear a few thou and everything works.

I included a pic of how I measured the depth so you can try and check it that way. Other than that you would have to pull the tail housing off and check everything to see what clearance you have.









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