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2 piece speedometer cables used on 78-9s with ST-10 trans
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am looking for advice/info on speedometer cables for 1978-9 Trans AM/Formulas with the ST-10 4 speed trans-
I have a few of these cars, looking at 2 of mine, I see there is an upper and a lower cable. seems strange but, if at least 2 cars have it, probably factory. The main cable comes from the speedo, through the firewall and down almost to the trans. Then, there is a connector, shown, and a shorter cable screw into that and then goes to the passenger side of the tailhousing of the trans. Am looking for this short, lower cable. Am sure it fits other years too but, no other Pontiac I have messed with ( hundreds of them ) have this set up. Who knows about them and where can I buy them? Would like to have my speedo working. Looking at the Ames site, they do not show this 2 piece cable deal. After calling them, they are not familiar with this set up. With many thousands of 4 speed Firebirds and TAs made in 78-9 alone, am sure someone out there must know on this. about 28" in length. probably used on other years as well thanks for any insight. |
I have a 79 4 speed but the car came to me in pieces so I have no idea on this part. It is interesting though. Could it be an add on to substitute for the lack of cruise control?
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i have a 78 W72 4 speed t/a with ~50k miles on it & original engine trans/rear & it has a solid 1 piece cable. cant confirm if its original though.
as mentioned above, sure seems like it would be cruise related that does use the 2 different length cables. interesting to see what you find on this. |
That Connector
That connector is a gear box for speedometer calibration.
I've seen them overdriven and underdriven. And I think I've got one here that's 1:1 ratio. Was told at a dealer the boxes were used with optional rear ends, instead of swapping gears in transmissions. Don't know them, but here's a place that makes cables and has the gear box adapters. https://speedometercablesusa.com/index.html Clay |
Years ago owned a fairly original drivetrain '77 Y81 4spd project car with 2 piece speedo cable. The lower cable was right at 2' ft long. The 2 piece cable & 1-1 adaptor was used to join the cables to make for better routing of the speedo cable with the pass side entry on the tailshaft of the 2nd design BW T10 trans. If you install a big output shaft Muncie in place of the BW, won't need a 2 piece cable, but will need the correct length upper cable.
Today, have '77 Y82 & '79 W72 4spd projects that are both missing their lower cable, so am in the same boat. There was also a Saginaw trans used in '76(?)-'77-78 F-body's which used a two piece cable, it's lower cable is slightly longer, have pulled a few. |
Theres a guy on ebay that is selling both cables.
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my 79 301/4spd TA looked pretty untouched when I got it. it has a 2 piece cable, but no gear box so it's 1:1.
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Have been dealing with 2-Piece speedo cables right much lately
(later 80's Dodge Vans) NLA on the one i need so have been having to "shop around" using diagrams pictures and specs - instead of part numbers and application. What are the specs on the cable ? 24" length - got that what are the ends ? need to know if male or female threads and whether 5/8" or 7/8" threads They look to both be female ends and both 7/8" But need to verify that - Exactly If they are both 5/8" female should be an easy find (about $20 or less off the shelf) If they are otherwise - it gets tougher. My 79 4-4-4 TA was 1-owner in 1985 with around 78k miles. It had a 1-piece speedo cable , but that doesn't mean it was 100% factory issue. The adapter gizmo and 2-piece cable probably was for the reason OPH mentioned - less stressful cable routing. The Lead cable was probably the same cable as one for an Automatic car. The cable i need is 65" - 70" long 7/8" Female 5/8" Male Can have it made for around $90-100 locally |
than you all for the replies and info so far. Am sure it has nothing to do with the cruise option. This applies to stick shift trans equipped applications for these cars.
I will loo into the ebay deal and report back. |
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Might not hurt to document the upper cable length and ends also.
While its a current topic. At bare minimum, can probably find a suitable 1-piece replacement in the $20 range off the shelf. On the 89 B350 Dodge Van, i had to go with a 1-Piece cable , for now. 102" - Plastic Snap-In upper - 7/8" Female thread lower = $16 off the shelf |
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Looked up the speedo cable offerings of the eBay seller's ( belair2door ). Just another Internet seller offering a part that is wrong. The fine print on his BIN of a lower cable notes "his" lower cable is 40" long & the factory piece is 26". Actually an original is closer to 24". The lower speedo cable used with Saginaw 4 speeds in late 70's low horse Camaros is closer to 26". Have to measure again, been a while, believe 27". I'm not piddling with low horse Saginaw equipped late 2nd Gens, but for many years pulled gobs of pedals, speedo cables, tilt columns, etc Last, if one wants to nitpick, even the sellers product year listings are wrong. No 4spd transmission avail in the 1980 Pontiac Firebird line. |
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If you guys can let me know the type of ends (male or female thread) , and thread sizes (5/8 or 7/8) , I have been going through all kinds of 2-Piece combinations/variables dealing with the Dodge Van. Have pretty good recall , and some other sources , for off-the-shelf cables. If all else fails you can have that 24" cable made from scratch for about $40-50 |
Todd, the '78-79 & 81 lower cable has the female grooved nut that attaches @ transmission & male threaded end that screws directly to another female nut on upper cable. Should be able to find the short lower cables I have from Saginaw installs. All are in large beef boxes from decades ago. As I haul more over & resort, there are always more surprises.
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Everything i have been dealing with has been either 5/8" thread female collar or 7/8" thread female collar at the transmission end of the cable. Really need to know thread size for the female end and male end. If Steve can check his sample. The Dodge Van uses a speed sensor in between the 2 cables - for the cruise control. It mimmicks the size and shape of the 1:1 gear adapter shown in Steve's sample. So when i saw that set-up , it is a similar arrangement type that i have recently spent hours and hours trying to find cables for already. |
Will need to confirm on the end my '79 T/A's upper cable, but am near 100% sure the threaded end is large, so 7/8", same size as the large threads on the end of the speedo sleeve in the tail shaft of transmission.
On a 70 M20 GTO Ive done one some work on, it has a 2 piece cable, & I believe it's a smaller in diam connection where the two cables screw together. |
Today, I pulled the main speedo cable out of one of my 79 400 Trans Ams. It measures 40" with the lower being about 27". I see Ames offers a single piece speedo cable that is 67" so, I think I will order that one and try it. If someone has a better idea, let me know. If it works, I will buy a 2nd for the other car, . This should solve the problem. Why, Pontiac made those cars with 2 piece cables makes no sense as it cost more money, more part numbers, etc, etc.
The end going into the speedo is 'convention' as is the end going into the trans. Should be pretty simple solution. we will see. |
RockAuto has them in 61" and 80" (1 piece design)
About $10 (Pioneer & ATP) They have the 40" --"lower cable"-- probably same cable as the guy on eBay for $10-12 O'Reilly's carry Pioneer Cables, and they ship free to the Store in 2-3 days. I bought my Pioneer cable for my Van from them, and it was cheaper than getting it at Rock and paying shipping. And quicker Steve, does the adapter mount to anything ? Or does it hang in mid-air ? |
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thanks for the info. The adaptor/joiner does not appear to mount on anything |
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