Ferrari Life Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
Ok so my dad has a 79 308 gt4 that has been a great car for the most part but is always plauged with minor issues. Naturually since he bought the car when I was younger I became a ferrari fan from day one and plan on owning one for my self one day. but for now i'll stick with my sbc v8 conversion 73 240z! I work on my car all the time I have completely rebuilt the suspension and converted it to all polyurathane bushings and coil over springs/struts. I'd love to start working on/learning about the Dino but dad is a little weary about me just diving head first into it. The speedo hasn't worked in quite a while and I believe that the sending unit/generator was changed a couple years back which made the speedo work for a couple days but then it quit again Does this mean that the actual speedo head ($450) is bad and needs to be replaced or that the dirty louisiana back roads that the car gets driven on have just caused another short in the wiring/sending unit? is the sending unit right behind the right rear tire? did I read that somewhere? can someone elaborate on this subject a bit so i can gain ole dad's confidence and fix the speedo so I can guilt him into letting me drive too? thanks guys!

-buck
 

·
Registered
Joined
·
60 Posts
hello,
check the odometer as well, there is an integrated circuit inside which are not very elaborated, often the problem comes from there. Depending where you are located, otherwise one company is on the west coast, and one is in Europe but hasn't the circuit in new anymore. (they use their last one for me)... good luck.
 

·
Premium Member
Joined
·
5,509 Posts
Unfortunately, the workshop manual is of no use for troubleshooting the speedometer. The most common problem with the 308 speedometer is the impulse generator and you are correct, it is located behind the right rear wheel. The location subjects it to all the water, mud, etc that the tire throws up. Since replacing it a few years ago fixed the problem (for a little while) then that could indicate this is the spot to look first. The first thing I'd check is the connection. Did the wire fall off after a couple of days and no one has checked it in 2 years? Make sure the connection is clean and tight (no corrosion). I think when I changed mine I put a few cable ties on it to hold it down. Next I would look at the impulse generator itself. Did the new one fail after a couple of days? Could be. I do not know if there is a way to test it. I see the price of a new one has gone up since I bought mine and now it is $225 through Dennis McCann. If we start to look at the speedometer itself, probably best would be to remove it and send it to Palo Alto Speedometer for repair rather than buying a new one. (McCann does have the speedo for your car for $405).

Probably best to do would be to double check all the connections and then maybe contact Palo Alto for advice, maybe they know how to test the impulse generator and they could give you an estimate for restoring the gauge itself.

I guess the next question is how much money are you willing to spend to fix it? Worst case you are looking at $630 to replace both the impulse generator and the gauge. The nice officer will tell you how fast you were going for about $100. If it has been broken for 2 years it obviously doesn't bother your dad that much and I really don't think a non-operational speedometer affects the value of this particular car all that much. Pretty much the only useful information the speedometer gives me is to let me know how slow the idiot in front of me is going. "Look at this idiot! The speed limit is 40 and he's doing 30!"
 

·
Premium Member
Joined
·
1,990 Posts
Pretty much the only useful information the speedometer gives me is to let me know how slow the idiot in front of me is going. "Look at this idiot! The speed limit is 40 and he's doing 30!"
HAHAHAHAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Good one Pete, haven't laughed that hard in a while......



~
 

·
Registered
Joined
·
177 Posts
Seems like mine is about 10mph fast, if I go the posted speed limit, everyone is passing me. Its like I have to go about 75 or 80 to keep up with the flow. I need to pace someone to see how accurate it really is, but I never seem to get around to it.

Cheers!
 

·
Registered
Joined
·
6,212 Posts
Seems like mine is about 10mph fast, if I go the posted speed limit, everyone is passing me. Its like I have to go about 75 or 80 to keep up with the flow. I need to pace someone to see how accurate it really is, but I never seem to get around to it.

Cheers!

Ferrari Speedos: Makes any Ferrari faster. How else would one be doing 10mph standing still :D

Mine seems to vary between 30-50...not always 10mph, but sometimes 5mhp
 

·
Registered
Joined
·
92 Posts
Tested with GPS, my 328 is absolutely 100% accurate (never seen that before) and the GT4 and 355 are about 5% out.

nothing to do with the topic, but there you go.
 

·
Administrator
Joined
·
15,140 Posts
Tested with GPS, my 328 is absolutely 100% accurate (never seen that before) and the GT4 and 355 are about 5% out.

nothing to do with the topic, but there you go.
I tested teh F40 with a GPS and the speedo is 7% off ----on the low side. When the speedo read 130 kph, the GPS was at 140 kph.:yikes:

Try explaining that to the police.
 

·
Registered
Joined
·
92 Posts
I tested teh F40 with a GPS and the speedo is 7% off ----on the low side. When the speedo read 130 kph, the GPS was at 140 kph.:yikes:

Try explaining that to the police.
changed tyre sizes? when i had mine, speedo read 4-5% high (didn't have GPS to verify, just timed with road markers)
 

·
Registered
Joined
·
6,212 Posts
You are more varried in the F40 because you are going faster than GPS can register :D


bet you'll outrun a missile, thus, your car is a national threat...look out
 
1 - 14 of 14 Posts
Top