Devdude

I am looking for input on how people that have done an LS1/T56 conversion have handled hooking up a speedometer. I know its quite common to leave it disconnected and guage speed using the tach, but my wife will be driving the car at times and I would be more comfortable having the speedo working. Any input you can provide is appreciated.

Thanks in advance

1991 Rx7 Convertible w/
1999 LS1/T56 ... stock for now...

custom13B

Check Grannys web page and read the install directions,specifically the wiring parts. Im pretty sure they have info to help you out. It may take a few clicks to find it but Im pretty sure its there. I have a LT-1 and it also uses a electronic speedo signal. Leaving it unhooked is a bad idea as the ECM gets a signal thru the speedo ckt and knows how fast the car is traveling,but this again is a LT-1 not a LS-1. I ended up buying a autometer electronic programmable speedo and modding my dash for it to fit. Wasnt difficult to wire it in either. let me know if Grannys page helps you more.

Ottoman

there's a converter box

speed singal comes in.. the box converts it to mechanical.. and spins a small motor that drives the hard line that turns the speedo

custom13B

Ottoman's right just dont expect the converted boxes to be cheap. Several companies make em. Only one I dont like is a version that drives a mechanical speedometer cable to retain a factory speedo. Read up on any one you decide to buy and talk to other guys using the same product before buying it.

89FCVert

I have a Speedo Box in mine, and you right it was not cheap. I think it was about 130/140.00 bucks...It works though.

custom13B

Thats cheap all the ones I found were 300+. Most parts designed for LS1 use are expensive by nature.

89FCVert

Im running a LT1

custom13B

So am I. But Devdude is using a LS-1 different animal. Thats why the boxes are usually 300+.

andrewb70

The engine makes no difference when it comes time to hook up the speedo. The thing to conside is that trans is on the engine. If both the LT1 and the LS1 have a T56 then the exact same process will be needed to connect the speedo.Neither the LT1 T56 nor the LS1 T56 have accomodations for a gear driven speedo. They both use a vehicle speed sensor. Manby use the Abbott Cable-X box to connect between the VSS on the transmission and the mechanical speedo on an FC.

Andrew

custom13B

Andrews right. I forget some LT-1's did have a T56....Ive never come across one but they do exist.....somewhere. When people are talking about LT-1's I relate to mine which came with a 4L60E. I dont like cable drive converter boxes as I said earlier so I didnt even consider them. I was looking at electronic conversions only. I was wrong and admit it.

owen is fat

the VDO brand of speedo in electrical (not mechanical) will accept the signal from the LS1 computer and they are under $140 shipped from Summit racing, you can find them on ebay once in a while.

mod the cluster a little and slip the VDO speedo right in place of the stock speedo.

andrewb70

To clarify even further, the 4L60E transmission also did not have a mechanical speedo drive. The 700R4 tranmission, which are essentially non electronic controlled 4L60Es have a mechanical speedometer.
Custom13B, this is probably what you have with your LT1 if your transmission has a mechanical speedo drive on it. There should also be another cable that runs from the trans to the throttle lever. That is the detent cable and controls the downshifting timing and line pressure. Make sure this cable is adjusted properly, as it can lead to tranny failure if its not adjusted right. I forget exactly what year the change was made from the 700R4 to the 4L60E, but it was somewhere in the 94-96 time frame. Do you know what year your LT1 is and what chassis it came from? Camaro? Corvette? There are also engines that look like LT1s but had iron heads. Those came in the Impalas.

Andrew

custom13B

I never said my tranny had a mechanical drive,I said I had a 4L60E which uses a VSS signal. My engines a 1995 from a caprice and it has iron heads and it is a LT-1. There are iron and alluminum head versions..the alluminum version makes a bit more power. Just because my engine has iron heads its not a LT-1..is that what your saying? I made sure it was a 5.7 liter,the aluminum head versions were not in the budget.

andrewb70

I just thought the Carprice engine might have used a different engine code, like the 96 Corvette that had an LT4. But it may not have:

https://www.rx7club.com/showthread.p...1&goto=newpost

Kind of like everyone calls the Gen III engines LS1s, but in reality there are a ton of different engine codes that were used in everything from the Corvette to Suburbans, to GTOs. Sorry about the misunderstanding about your tranny.

Andrew