I put new 4.10's in last week (had stock 3.42.s). the best i could do last night was a 13.40 (2.08 60 ft) and before i was a consistant 13.1 with a 2.1xxx 60 ft. I even had a 1.99 60 ft last nigt and i ran a 13.5. anyone with 4.10's can you tell me where to shift with the stock tachometer? I used to shift at 6400 rpms but iknow that isn't possible with the 4.10's since it revs faster, but how much faster? I know for a fact that i hit the rev limiter once on every pass and sometimes more than once.

 

Does the engine still make power higher than 6400?

If you were shifting at 6400 with 3.42 gears, what rpm were you at when you crossed the finish line? If it was at or near 6400 rpm then your setup was perfect before.

Going to 4.10 gears means you either need to increase your shift point, if there's enough left in the engine, or install taller tires. Chances are you have a stock height 26" tall tire. Going to a 27 or 28" tall tire will allow you to go back to shifting at 6400.

The tire size/shift rpm/gear ratio all depend on what rpm you cross the finish line at. A perfect setup should have you crossing the finish line a couple of hundred rpm above your shift point. The car is then maxed out for the 1/4 mile.

 

right now i'm running 25.75 inch tall tires right now, i'm thinking i may have to shift to fifth.

 

Am I missing something here? What does a rearend gear change have to do with someones ability to shift a manual transmission at a certain RPM? If he's hitting the rev limiter before he shifts because the car is accelerating faster, then he needs to adjust his anticipation of when to shift instead of waiting until he sees the needle on the tach reach 6400 before he starts to move his body parts to shift. Maybe try STARTING the shift at 6300, or even 6200 if his reaction is slow.

blk01z28:
You had your best 60' with the 4.10's but the ET was off. There are a lot of things that could cause a slower ET, starting with hitting the rev limiter. Even with an A4, when my car was hitting the limiter in first gear due to the PCM programing, the car would slow down .2-.3 with similar weather conditions. If you were hitting the limiter in 2 gears it's not surprising that you slowed up .4, especially if the weather wasn't as good as it was when you ran your best numbers. But like I said, there's a LOT of things that could have caused the car to slow up: Dirty air filter, head wind at the track, winter grade gas in the tank, etc., etc., etc.

 

Where in that first post does it say he has a manual transmission?

Changing the rear end gear will have nothing to do with the shift point but it will affect the amount of distance that is usable to get down the track in the same rpm range. If a deeper gear ratio is used and the same shift point is used then you'll run out of track before you hit the red line if you crossed the finish line at red line with lower gears before.

You should never have to use OD in a drag race. The OD gears are small and weak. You should be crossing the finish line in 1:1 gear.

The 4.10 gears will multiply torque more than the 3.42 did so you will have lower 60' times. Too much torque and the wheels could break free and you'll have wheel spin. You could use 4.56 gears and get great 60' times but if the engine can't rev high enough going through the gears, you'll run out of track before running out of gear.

Pro Street type cars may run 5.13 or deeper gears. They usually also have 33" tall tires to make the gears more streetable. Drag cars with 30" tall tires and 5.13 or deeper gears usually shift at 7000 rpm or higher to get down the track.

 

• (had stock 3.42.s).
• Pro 5.0
• can you tell me where to shift with the stock tachometer

With my 4.11s in my M6 I shift at 6300 and have not needed 5th gear in the 1/4 mile.

Just keep practicing m8!

 

Thank you NO-Ten83 for answering his question

I have 4.10's and an A4 with 25.5" tall tires (16" BFG DR's). Running 12.4-12.5 I cross the line at ~6100 in D (1:1), just short of my 6300 shift point.