i'm swapping my 3.08s for 3.42s. what's the best way to correct the speedometer?

get a new vehicle speed sensor. they are like 60 bucks and easy to swap. i dont know the part number you will need, do a search and you will find it.

I asked this same question a couple of days ago. I've gotten conflicing answers though. You'll need to swap you speedo gears in the transmission. In my 700r4, I went with a 15 tooth drive gear and 42 tooth driven gear. My speedo was very close with this combination, but I think that either a 41 or 40 tooth driven gear may have been even better. I'm sure someone will point you to 700r4.com's gear calculator or TCI's website, but I've gotten different results from both of them and yet a different result using the method from the tech article on this site. Hopefully someone else can say for sure, but I think that the 15 tooth drive gear and either a 41 or 40 tooth driven gear are your best bet, provided of coarse that you have a 700r4 and stock diameter tires.

i have a manual (t-5) transmission. does that make a difference/

You need a purple drive gear and a white driven gear.

Pete

can anyone tell me where i get them?

Oops, I missed your sig saying that you have the t-5. I don't know if the gears are the same or not, but I got gears for my 700r4 at a local gm dealer.

I had my gears, posi, and speedo gears ready to go in before I wrecked the thing and I got them from my dealer. I can get you part numbers but I am away from the parts. I do belive I spent roughly 30-40 bucks total. Your tranny will need to be dropped to change these gears. And yes one is purple and the other is white pressed fit onto a little metal bar.

The gears for a 700R4 are different than those used in the T5's. I'm not sure about sources for new ones - a dealer would be the logical place - but you could look in the salvage yards for an 86-up T5 equipped V6 Firebird, as they commonly used a 3.42 rear gear.

Pete

Ok I am home now and have the parts for the T-5 and 3.42 speedo gears right in front of me.

I purchased one from the dealer and another from www.gmpartsdirect.com. If I were you I would go to the dealer and get both. Easier and takes less time than finding a car in a yard and dismantling it to get what you want. Too much work for 30 bucks worth of parts. Ok here we go...

For the round purple one

GM# 14071731
ACD# 14071731

For the white one on the metal shaft (AC Delco part)

ACD#14090592
GM#14090592

There ya go

One more to see the sticker/paper work on them