Alright, I've heard everybody saying they were going to swap their slower speedo with the popular 145mph speedo, but never tell if it worked.

This has been confusing me for months, My speedo, which is a 115mph cable-driven, has gone to pieces, and what I am wondering is, if I change my speedo to the 145mph, will the needle be calibrated and lined up where it should be? So if I'm showing 55mph, then I am really rolling at 55mph.

Bascially what I am wondering is this, Can I just easily swap my 115 gauge to a 145 gauge, without and other modifications or swaps?

Thanks,
- Justin

 

yup, just get a mechanical one as well. As long as your speedometer gears in the trans were calibrated properly and you were showing the correct speed before you swap, you should be fine.

 

I thought something was differant 89-up,not sure though.its simple to tell once you get the old one out if the replacement is the same.

 

it was ummmm 1990 went to an different style, 89 and below are ok, some early ones had the "Dual Pointer" but it still the same as a single pointer as for the speedo gears....

some Berlinetta's had a special digital one also

 

82-84 had the dual pointer, 85-89 the single. All mechanically driven. 90-92 were electric. No experience with Berlys.

JamesC

 

A mech speedo swap is just that, a swap. Now when you start changing gears and tire size is when you need to worry about speed differences.

 

Can I swap my 1984s 85mph speedo with a 145mph speedo?

 

As long as the 145 isn't from an 90-92 car, you can swap.

JamesC

 

If it is the "normal" (not the berretta double needle) style, then yes you can swap out the speedo. I'm not sure about how the berretta style would work.

but...

The only thing that can be a problem, from what I was told on here, is if you swap the whole gauge cluster, wierd things usually start to happen after a while. So the suggestion is to just swap the speedo only.

 

Will I need to adjust anything for it to work rite?

 

nope, shouldn't have too. just plug and play with the cable!

 

Just to clarify, all mechanical speedos, 82-89, are interchangeable. If the trip doesn't work, check the following link:

https://www.thirdgen.org/forums/faq-...-fix-pics.html

JamesC

 

Mine has the double needle so it has the mph on one side and the kmh on the other side.
----------
link does not work.

 

Doesn't matter that the speedo's a dual pointer. The link works for me.

JamesC

 

I did the swap on an 84 Z28 with the double needle. I went to a NOS 140 Z28 speedometer that GM offered as an upgrade. The calibration was WAY off. Showed I was going 100 MPH at about 60 MPH acual. The fix is to get a speedometer calibrator. There are a number of companies on the internet that will build you one. (Any Speedometer shop) It's a small mechanical device that screws into your transmission where the speedometer cable normally goes. Then the cable is screwed into the calibrator. I bought mine on the internet for $65.00 They figure out your ratio by having you drive a one mile course. You chart out exactly 1 mile on your local road or hwy. Set your odometer/trip to "0" You then drive that one mile course and stop. You then record what your odometer/trip recorded. Mine recorded something like 6/10 of one actual mile driven. You then give them the figure and they build the calibrator for you. Mine worked to within 1/2 mile per hour. The only other way is to swap out your drive/driven gear, which on a T-5 means taking off your tailhousing.

 

If all is stock in the car, there is no need to calibrate anything, simply swap one speedo head for the other. A rear end gear change is another story.

JamesC

 

Nope, that's why there's so many different drive and driven gear combinations. There's a number of different speedometer face plates. 85, 110, 115, 140, 145, and a bunch I've probably missed. Although the speedometer heads are all engineered the same, the ratio in which the mechanical cable is turned is different, therefore you're going to get a different reading for each depending on the face plate you use. Thats why you can't simply screw on a new face plate and hope it'll work.

 

I'm unsure why the reading on your speedo was off. I do, however, stand with my previous statement. Good luck.

JamesC

 

False false false, the reason for all the different drive and driven gears are for the different rear end and rear tire size options avaible thoughout the GM lineup.

https://www.thirdgen.org/gauges

 

I've swapped speedo's (85's to 115's) in three thirdgens now...they all work fine and accurate.

 

Ok I just read over the artical in the link. I didn't replace my sending units for my temp or oil pressure and now they just tack out I would like to replace these. Now my question is where are they both located on my vehicle?

 

temp sender that feeds the guage is screwed into the cylinder head on the drivers side between #1 and #3 cylinders. Be careful when removing it is in the water jacket and will puke coolant all over.

Oil pressure sender, IIRC is on the back of the motor somewhere, do a search as I am sure this has been discussed many times.

 

I swaped the entire cluster 2 years ago and it works fine for me. I'm not sure what wierd things your talking about.

 

There can be electrical issues from time to time (I'm not sure why). If your cluster functions as designed, any possible issues can be avoided by simply swapping the speedo head. More often than not, however, a swap is straightforward.

JamesC

 

When I did my 92 145 speedo swap in my 91 RS, I changed the whole cluster. The tach was acting weird, so I pulled the cluster back out and swap the tach PC board from my original cluster into the 92 cluster. Fixed it, no other issues.

 

I wasn't aware that there were any mechanical speedos that read more than 85mph....or is that only in the Camaro's?

I also know that in firebirds they went from Mechanical to Electrical in 85...so I'm sort of screwed with my 84. I would love to get a 120 or 145 gauge for my T/A.

 

Wouldn't that be overkill?

JamesC

 

I don't get the joke?

 

Just poking a little fun, suggesting Ozz's car didn't need a 115 or 140 speedo because his car wouldn't go that fast.

JamesC

 

GAH, I didn't get to the post first. HA...

You're right, my car would probably explode the moment it hit 90! haha

 

I don't know--I read somewhere that the top end for an HO car was 138. Anyway, I have a terrible screechy noise from the passenger side when I hit about 90. It keeps repeating, "Now, you slow this car down right this minute!" Which begs the question of why I need a 140 either.

JamesC

 

We're talking mechanical, you're talking electronic.

 

Please post your MPH results when you get your project done. Hope it works well for you.

 

We were discussing general electric issues in a swap, not the speedo specifically. Those electronic issues can crop up regardless of year and type. Forgive me for saying so, but you seem to hanging on to a belief that's simply incorrect. Perhaps trying a search will provide you will a wider range of opinion than the ones expressed in this link.

JamesC

 

HAHAHA Amen to that!

 

That was very politely stated. I've been searching as to why my application didn't work without the adapter. The speedometer shop said that my 85 mph speedometer was set up for a 19 tooth driven gear with a 7 tooth drive gear. The 140 MPH speedometer required a 22 to 9 combination to get the required 1000 revolutuions per MILE needed. Although there's a lot posted on this subject, I have yet to find a post that said a double needle 85 MPH speedometer was successfully swapped and calibrated for a 140/145 MPH speedometer without an adapter. Thanks for being so patient.

 

We shall find out. I am getting ready to swap in a 88 iroc guages into my 82. I already have the sending unit. Tonight I tried to get the fitting for the mechanical one out and couldn't. Have to figure out how to get it out.


Vince

 

Um yeah, I can read. I put my experience in this thread so in the future, when someone with a 90-92 does a search a finds this thread. The info for 90-92 swaps is in hear. And the tach thing I was commenting about, could apply to earlier models. I just wanted to point out that if you did a whole cluster swap and the tach seems off, you could just switch the PC boards for the tach, at least in my case of putting a 92 Z28 L98 dash into a 91 RS LO3 car.

 

Humm, I would have thought that your HO car would have had 3.73's, not 3.42's. I'm not familiar with a 9/22 combo, but it sounds close to what you'd need for 3.73's. Note the tooth count for various ratios below.

3.23's up require a blue 7-tooth drive gear, plus the following driven gear:

18 tooth (p/n 3987918) Brown = 3.23
19 tooth (p/n 3987919) White = 3.42
20 tooth (p/n 3987920) Blue = 3.45
21 tooth (p/n 3987921) Red = 3.73
22 tooth (p/n 3987922) Gray =3.77

3.08 has an 9-tooth drive gear.

Given that info, could your car have had the wrong gears to begin with? Perhaps a change (trans or rear) was made by a previous owner.

JamesC

 

i think i have a simple solution to your problem and maybe i can give some advice from my own expieriance. i did the 115 to 145 swap on my 89 iroc. the speedo worked fine once i got the cable pluged all the way in. the electrical trouble is from a bad connection. you have to push pretty hardon the header plate and the face of the cluster. i know this because some of my gauges were showing that they were maxed out. after i fixed the problem it has worked flawless for 4 years. as far as trying to go with diff year speedos just try to find a way to drive both of the at the same rpm (like with a drill or something) then see if they show the same speed. i,ow need to find a way to change over to the 91-92 electric cluster to get my speedo to work with my 6 speed tranny. stupid electric vss.

 

Once again, if nothing has been changed (tranny or rear), the speedo swap is straightforward and nothing needs to be changed.

JamesC

 

Ok I found out that my oil pressure sender unit was not connected as in no wire to it. Now the thing is I can't find the wire that connects to it anywhere under there can some one plz take a picture of the area for me so I can at least know what I'm looking for.

 

Ok I couldn't find a 145 speedo so I settled for a 115 speedo and swapped that in. I have a picture here it is. looks good but I cant see if it works till I replace my broken speedo cable.

 

nice lookin dash, guage faces arent sun faded at all

Dont forget when you put your new cable in to lube it

 

I never forget to lube it

Yea and I have t-tops

 

If you like a bit of color in the cluster:

https://www.thirdgen.org/forums/body...r-cluster.html

JamesC

 

so im sure this has been asked somewhere.. and i havent found it but.. can you.. or how much of a pain is it.. if you even can... swap the 85-89 guages into a '90? i prefer the full round gauges versus the half moon.. plus the gauges on mine dont work well anyway.. gas is WAY off and tach doesnt work at all... is it possible..?? a pain in the ***? or no way in hell will it work? thanks.

 

No. The 82-89 clusters have a mechanical speedo, the 90-92 electrical. The clusters are also shapped differently. Without major modification, you can't swap.

JamesC

 

well that sucks, but appreciate the info thanks!

 

how do you lube the cable?