[Pepi]

So how many people have seen the speedometer cable routed underneath the transmission and how many have seen it routed over the transmission?

Just trying to get a sense of which way is correct?

[johnta1]

Do you have the assembly manual?

I think it shows or implies it is on top of the tranny?

[Held for Ransom]

Assembly sheet would be 12J-10.
My '74 L78/M20 is under with clip on the inspection cover bolt.

[Pepi]

I looked at my assembly manual for that sheet, and it is hard to tell, but looks as though yes it attaches to inspection cover. I was just surprised to see Bentwheelbob's like that, because I don't ever remember seeing it like that. I know mine goes over the top, and bent so perfectly like that, I always just assumed that was how it was routed. I have never had that clip on the inspection cover. Something else I will change to make correct. Now just to look for the correct clip.

Still interested to see how many have them going over he top and how many are under.

[johnta1]

It looks like the cable is bolted to a tranny bolt at the bellhousing with a clip.
Can't tell which one.
It could be a bottom one.

[johnta1]

Here is a scan of the cable.

I thought the 'underbody' was the tunnel, which the cable appears to follow?

I highlighted a bracket which I'm not sure where it is.

[Pepi]

Here are pictures of how mine was routed. It goes over the transmission and uses a clip on top on the passenger side.

John, yes that is what I see, and I always thought it was just below the tunnel also.

[Bentwheelbob]

I'm beginning to think my assumption was wrong, but wish there was more definitive guidance on this. The tranny had not been out and I can't explain the clip on the dust cover???

[dpoltzer]

I have owned several 4 spd. cars over the years and the cable has always been routed over the top and not under.

[Pepi]

Originally Posted by Bentwheelbob

I'm beginning to think my assumption was wrong, but wish there was more definitive guidance on this. The tranny had not been out and I can't explain the clip on the dust cover???

Bob,

Your clip on the cover almost seems to coincide with the assembly manual, but it is hard to see it for sure. Hopefully by the beginning of August I will be up to see my brother's 75 TA and that I know has never had the trans out. I will check and see how that one is routed.

dpoltzer,

Nice to hear of more that have been routed over the top. I am hoping to hear from more members to see what they have seen.

Now I have to watch for that on any underneath pictures.

[Held for Ransom]

Just so we're clear.

Mine has two clips, as pictured in the assembly manual. One on the lower left transmission bolt and one on the inspection cover bolt. Here is front/back shot of the cover clip.

Have you posted this question in the '74-6 Firebird section?

[eaglesan13]

On a related topic, why do some cars have a speedo cable adapter while others don't? This is a picture of my 70 Formula, (with the original trans) and it has the adapter. I have seen this on some other 70's also. My car came with an M20 with a 3.55 posi.

[Pepi]

Originally Posted by Held for Ransom

Just so we're clear.

Mine has two clips, as pictured in the assembly manual. One on the lower left transmission bolt and one on the inspection cover bolt. Here is front/back shot of the cover clip.

Have you posted this question in the '74-6 Firebird section?

I have 2 clips, but they were both mounted on the top 2 bolts of the transmission.

No I haven't posted in the 74-6 section. I will do that also. Done.

[TA455HO]

Originally Posted by eaglesan13

On a related topic, why do some cars have a speedo cable adapter while others don't? This is a picture of my 70 Formula, (with the original trans) and it has the adapter. I have seen this on some other 70's also. My car came with an M20 with a 3.55 posi.

The speedometer heads were calibrated for a specific tire size, transmission and rear end ratio. If parameters start to fall outside of the values used for the calibration then an adpater is commonly used if the speedo driven gear can't be changed enough to get an accurate final reading.

In 1970 there were 4 combinations that used an adapter and 12 combinations that did not.

In 1971 speedo cable routing was carryover. The number of cables was reduced by one due to the elimination of the adapters on automatic transmissions. The only adapter used was the Right Angle Adapter 6477964 used on the R.H. side of the manual transmissions, but not with a 455 engine.

.

[superdutybob]

When I got my 74 SD 4 speed car it had the cable mounted over the transmission. Can't state whether it was correct or not. I can ask the question "why would you change the routing if it was originally under?"

Brewsters 73 SD 4 speed, which was a meticulous concourse restoration, had it mounted under and clipped to the dust shield. That always made me wonder if mine was wrong. I never changed it.

[TA455HO]

Could be same reason you see the cross-member bolts put in the other way - it's easier when you go to put it back together. Those crossmember bolts are put in from the topside at the factory and it makes sense so if the nut drops off you still have a bolt going through the hole. But, since it was done before body drop it was possible. Getting them out without loosening the subframe enough to get some clearance and they are nearly impossible to remove. When putting them back together it was not uncommon to put the nut on the top side and the bolt up from the bottom. True, if the nut comes off, the bolt immediately falls out on the ground and you are left with nothing at that hole. But, mechanics getting paid for the job or by the hour are going to take some shortcuts.

Not saying it would positively apply to a speedo cable, but never know what might happen if a transmission gets pulled at some point.

.

[455hota]

My 70 TA with M20 4 speed and 3:55 gears does have that same speedometer adapter. I was wondering if it was correct as well. I guess the answer is yes!

[Pepi]

I wonder if it had anything to do with the cable hanging low and possibly getting caught on something. Up and over protects it more. I know the parking brake cable is down under the car also, but seems to be pulled up higher.

[Bentwheelbob]

Yeah, I have thought about it's potential for damage. It is of course above the exhaust, and it is above the level of the subframe arms. Still it seems a little like the cable on an aircraft carrier just waiting to snag something...

I was beginning to think I had the incorrect routing until I heard about Brewster's Brewster. I wish he would weigh in here.

In the end, it will just be good figuring out the correct way(s?).

[Held for Ransom]

I just came in from the storage area and had looked at the inspection cover bolt on the '73 400/4 speed combo I have (no clips). It's approx. 3/8" thread vs. the approx. 3/4" thread on the '74 with the clip.