BlueZee28

iTrader: (30)

I yanked out my factory 2.73 rear end from my car and installed an LS1 3.42 rear end. What color, or how many teeth are on the speedo gear I need to buy?

I called up the local stealership and told them what gears I put in the rear end and they don't know what speedo gear I need because the part numbers and descriptions don't specify what gears they are for. They said I need to tell them how many teeth are on the gear I need or what color it is, because they are color-coded from GM. It's for a 700R4, stock gearing in the transmission. Only thing touched is the 10 bolt.

Thanks guys.

Bomber

I would not know which one to tell you but if you happen to find a vehicle just like yours ( tire size , height of the tire and same rear end gears) then drive right next to each other , get the speed off of that car and get the speed off of your car and then compare the difference. after you found the difference then its easy from there what you need to do is I think increase the number of the teeth to get more MPH or its just the opposite I dont remember. but its 2 miles per tooth. I hope this helps

BlueZee28

iTrader: (30)

Are you positive it's 2 mph per tooth?

camaronewbie

www.700R4.com

They sell the speedo gears, and their website has the converter on there somewhere. You'll have to change the drive and the driven gear both. One is on the tailshaft spline (remove the tailhousing), the other in the speedo housing. Sorry, can't remember which colors I got when I did this.

You'll lose tranny fluid when you do this - it's a good time to replace the tranny filter, and add that drain plug to the pan so that next time getting the fluid out means a drain, and not a big puddle! This could be shift kit time as well (while you are there)!

Know one other thing - your stock spare tire will NOT fit over those LS1 disc brakes. (I did the same swap last year)

Kevin91Z

iTrader: (1)

This is such a common swap that I cannot believe a search for "3.42 speedo gears" did not get you any results.
I believe its a 15 tooth and a 42 tooth you need. You'll have to buy a new sleeve for the 15 tooth, as well, as I think you have a 17 tooth stock, and its not compatitible.
If I'm wrong, I'm sorry, but you'll find it for sure in a search.

camaronewbie

Oh - the speedo gear "sleeve housing" - most the websites I saw told of needing a new "sleeve housing" because the stock one wouldn't fit over the new larger gear. I stuck my new gears in my old speedo sleeve housing on my 1992, and I haven't had any problems at all in the last year - so you may not need this new sleeve housing - it's an extra $60!

And IIRC I went with the 15 tooth drive gear and the 40 tooth driven gear - this was with 245/50 16 tires and 3.42 rear gear - some others have done a 41 tooth driven gear.

Do get a new speedo housing O-ring, and the clip that holds the drive gear on the tailshaft - hope any of that helps.