rearend question

ok a few week ago i put an 87 iroc rear end into my car (91 rs w/ a 305) to get the posi well my gear originally was a 2.78 gear and now its a 3.23 gear how much does this effect my speedometer??? also i put four wheel disc brakes on it w/ new calipers on the back and i had to change to proportioning valve i guess its called which was costly but my brakes still dont seem to work much better if any.... there seems to be more play in my brake pedal and when i let off the gas to naturally slow down u can hear a wobbly type noise in my rear brakes.....a mechanic said it was due to the fact i didnt reconect my e brake and the braket i no longer have for it buts pressure on the brake not lettin it wobble if this is true i will go get one immediatly just figured id ask the experts first thanx!!

it's probably about 10 mph fast

actually it will vary at different speeds. it might be 5mph off at 25, and 10mph off at 60 etc.

did you bleed the brakes?

yeah, if you put in diff gears, its gonna throw off the reading, what you should do, is if you can, go back to the car you got the rear out of, andpull the speedometer output out of the tailshaft housing of the tranny, the gear on the speed sender should correct your speedometer. you can tell by the color, if the color is the same on the sender, get the gear off the output shaft of the tranny, youll have to take off the tailshaft housing to get to it. pull up on the little metal tab, and gently, tap off the gear, it should slide down the shaft and off. put it on yours the opposite way. the sensor comes out with a single 10mm bolt i think, and the tailshaft housing is held on by 15mm bolts and i think there is a 7/8in nut, and a 10mm nut holding the torque arm braket on. also, the cable comes out of the speed sender by unscrewing the outer part of the cable, and then it pulls off.

I ordered a brand new drive and driven gear for my speedo and tranny because of my gear swap and brand new from the dealership I think the parts cost me around 80 bucks canadian. Shouldnt be more than 50 US, especially if you can just order them from gmpartsdirect.com

what seems to have happened w/ your brakes (the same that happened to mine when i swapped rearends) is you've blown your boost valve, or i think that's what it is called. basically your brakes are stronger, but instead of having power brakes, you are runnin regular brakes. i blew my boost valve too when i bled them for the new rearend. if your get that replaced all should be fine.

what seems to have happened w/ your brakes (the same that happened to mine when i swapped rearends) is you've blown your boost valve, or i think that's what it is called. basically your brakes are stronger, but instead of having power brakes, you are runnin regular brakes. i blew my boost valve too when i bled them for the new rearend. if your get that replaced all should be fine.


R u talkin about your proportioning valve or compression valve some people call it because i replaced this part because b4 i did i had barley any rear brakes cause it was sending no where near enough pressure to squeze the calipers in the rear it was only sending enough to press in drum brakes i used to have but i replaced that and get decent braking but still not great and like i said my pedal is very spongy sometimes more than others and when im at a stop to hold it there i almost have to press the pedal all the way down

yeah sounds like air in the system, or a leak somewhere or something along those lines.

Here you go, just plug in the numbers:

http://www.f-body.org/gears/