Factory speedo, LED tach question

[Red Regal T]

I just re-installed my factory analog speedometer. I removed it a few years ago because the circuit sheet on the back of the case was bad. I had forgotten the tach was stuck all the way over. It just stays there. The boost LED works, but of course, it's off, but at least it moves. I was wondering if anyone knows a simple fix for the tach. Seems like it's just grounded or something like that. Also, a few years ago, I found a 140 mph speedo at the junkyard in a Riviera. I installed it also but unfortunately, it reads about 35 mph too fast. GN speedos use the orange gear in the trans. I'm going to try some different color gears. Anybody try this with success?




.

 

[TurboBob]

caspers fixes those, but it looks like your boost gauge has a couple LEDs out. You might need to hunt down a core.

Bob

 

[turbo nasty]

You can get the speedo recal'd at a speedo shop. Leave the orange gear on the gov in the trans as its for the 3.42's..assuming you still are running that gear.

As far as the tach/boost gauge goes Caspers will take care of it

CEI - Casper's Electronics, Inc.

 

[novaderrik]

GM speedo heads are all calibrated the same- 1000rpm's at 60mph. if the speedo is off, then there is a problem internal to the speedo, but it's probably just that the speedo head never got calibrated to the 140mph overlay that was put on it.

 

[Red Regal T]

But, I pulled the 140 mph speedo from a Riviera. It is not an overlay. It is the factory piece. So, wouldn't the plastic gear in the tail of the trans govern it's calibration on the speedo face?

 

[Red Regal T]

I ran across this speedometer reducer for $62 which is within reason. It can be programmed to reduce speed 50%, 37.5%, 26.7%, 17.6., and couple more. Hasn't anyone who purchased a 145 mph overlay fixed their speedometer so it reads the correct speed or something relatively close? If so, how did you do it?

 

[aminga]

I ran across this speedometer reducer for $62 which is within reason. It can be programmed to reduce speed 50%, 37.5%, 26.7%, 17.6., and couple more. Hasn't anyone who purchased a 145 mph overlay fixed their speedometer so it reads the correct speed or something relatively close? If so, how did you do it?

Don't use that it will affect the VSS. Have the speedo head recalibrated

 

[azbob]

Put the 145 overlay in and had the speedo head recalibrated. All that was done was movement of the magnets on his machine showing 60 mph. He told me that the readings would be off at upper speeds over 100 and I told him at those speeds I am not looking at the speedometer. Do not fool around with the gear reducer. My speedo guy did it for free as it took all of three minutes.

 

[Red Regal T]

Thanks guys, I'll look into it.

 

[Red Regal T]

OK, called a couple speedo places around here, and now I know why I didn't want to deal with these people. First smart ass wanted to put my car on a dyno to get the "accurate" information so he could correct speed reading. Of course, that requires he remove the speedo from my dash, the speedo I have already removed that's in my hand. He also wanted to argue with me. He resented I told him the car was a Regal ... "Grand Nationals are different", he says. "Riviera, Regal, and Grand National speedometers are all different", he says.

NO THEY'RE NOT DIFFERENT! But I kept my mouth shut.

I didn't even want to bother arguing with him. Know it alls know it all.

Then, I call up another place who said if he had to deal with the speedo head, he'd have to change hair-spring after hair-spring to get the correct reading. So, by what these two speedo experts have told me, it ain't no easy or inexpensive job.

So, it's back to the reducer idea. What is the downside as far as the VSS is concerned? Is there a downside? I'm not clear on that.

 

[Red Regal T]

Just realized, regardless of the VSS the odometer would be off with that reducer. I'll just put up with the incorrect speed reading. I have the scanmaster if I need it.

 

[turbo nasty]

The speedo reducer will cause a few issues off the top of my head.

L/U MPH will be off

Speedo will read correct but the VSS will be reading wrong. i.e.- the speedo 145 faceplate will read correct but the VSS will be reading and telling teh scanmaster slower than the actual roadspeed. Faceplate say one thing SM another.

Everythingthat is MPH affected in teh ECM will be getting a BS reading witheth reducer

My understanding is a "good" speedo shop will alter the magnetics in the head of the speedo to get it in the ballpark. I may be wrong but Im pretty sure its something along those lines

 

[Red Regal T]

The speedo reducer will cause a few issues off the top of my head.

L/U MPH will be off

Speedo will read correct but the VSS will be reading wrong. i.e.- the speedo 145 faceplate will read correct but the VSS will be reading and telling teh scanmaster slower than the actual roadspeed. Faceplate say one thing SM another.

Everythingthat is MPH affected in teh ECM will be getting a BS reading witheth reducer

My understanding is a "good" speedo shop will alter the magnetics in the head of the speedo to get it in the ballpark. I may be wrong but Im pretty sure its something along those lines

Well, besides whatever the VSS would do, I didn't factor in the odometer with that reducer, so I'm no longer considering it at all. Yeah, I thought I could just have the speedo head modified as suggested in a post above, but this guy wanted to do the full procedure. I don't know what he would have charged, but I think more than I want to pay. There are only two shops in the area, and the other guy didn't even sound like he was a business. So, I'll just stick with what I have. Regardless, thanks all of you for your suggestions.

 

[azbob]

+2 with Turbo nasty.
To verify my vss output, I checked the final shift point into fourth gear. It is supposed to occur at 42 mph according to factory specs. Well mine shifts at 43-44 mph on my 145mph overlay after I had the magnets adjusted as stated previously. That is close enough for me. I have dealt with speedometer reducers on GM "A" body cars that I restored and found the "hit and miss" game not very exact. That is how I developed the friendship with my speedometer guy. Sorry for the late post, I was typing and did not see your latest post.

 

[Bigjack7440]

As far as the tach stuck all the way there are two wire ends hanging off your alternator, they should not be plugged in together, and if they are not then you have another issue!I think one is green and one is orange make sure they are not plugged up to anything. I don't what they are for but they look like they are made for each other but they will lock your tach up. Don't ask me how I know this lol !