4l60 4th gear useable?
Thread Starter
Advanced
Joined: Sep 2020
Posts: 52
Likes: 3
From: kalamazoo michigan
4l60 4th gear useable?
Has anyone here used 4th in a 4l60? i have a stage 5 built by rpm.. i ran into this problem while building my vette. i used a stage 2 rear diff (4.10) thinking i was going to build a nice 450 rwhp street car.. how ever that went out the window and it turned into a 600 rwhp monster...aside from the 3.06 first gear problem i have has ANYONE used 4th gear? Does it pull? does it just quit. im assuming ill be using it in a quater beings my calculator says it will only go 120 in third with a 28inch tall tire...
Last edited by donnysvette; Dec 17, 2020 at 08:14 AM.
Le Mans Master
Joined: Mar 1999
Posts: 6,029
Likes: 85
From: Palm Coast, FL
My 4L60 went 9.5X @ 145 on a 100 shot of nitrous, we had to use 4th gear. I was running the 3.73's. N/A would cross the line in 3rd (Low 10's). Afterwards we decided to "harden" the trans. 
Le Mans Master
Joined: Mar 1999
Posts: 6,029
Likes: 85
From: Palm Coast, FL
It was tracked tuned at the time. When it did finally hit the dyno, it was in the 425 range ... 435 (after tune) RWHP ballpark on a stingy Mustang. I had just installed a Holley Dominator V2 on it to control the N20 but never used it. Was wanting to see what 300 shot would do, it never happened. Was thinking low 9's.
Edit: There is a vid in my sig of my 98 and 04 running low 10's na with 425 rwhp.
Edit: There is a vid in my sig of my 98 and 04 running low 10's na with 425 rwhp.
Last edited by Rob Petyo; Dec 17, 2020 at 09:28 AM.
Safety Car
Joined: Oct 2007
Posts: 4,222
Likes: 1,078
From: South Florida
The rule of thumb for race cars (actual race cars, not stree/strip stuff) is never use overdrive.
The unfavorable ratio (torque reduction) will slow the car down.
That said, if you run out of rear gear, you can either keep revving the engine, or use overdrive to achieve more MPH
In those situations it is better to change the rear gear and/or tire size, so the car can continue to use 1:1 (3rd gear) ratio and avoid overdrive.
However, in a pinch, for non-competition cars (not a true race car, just a toy) overdrive MIGHT be used.
The final question is, can the transmission support high torque through the overdrive gear?
Some transmissions, such as 4l80e, can NOT. 4l80e will break easily if you try to use 4th gear to support any measure of "real torque" (say 500+ ft*lbs) for long.
Can the 4l60e? I don't think its a good idea.... but... Ask your transmission builder imo.
The unfavorable ratio (torque reduction) will slow the car down.
That said, if you run out of rear gear, you can either keep revving the engine, or use overdrive to achieve more MPH
In those situations it is better to change the rear gear and/or tire size, so the car can continue to use 1:1 (3rd gear) ratio and avoid overdrive.
However, in a pinch, for non-competition cars (not a true race car, just a toy) overdrive MIGHT be used.
The final question is, can the transmission support high torque through the overdrive gear?
Some transmissions, such as 4l80e, can NOT. 4l80e will break easily if you try to use 4th gear to support any measure of "real torque" (say 500+ ft*lbs) for long.
Can the 4l60e? I don't think its a good idea.... but... Ask your transmission builder imo.
Thread Starter
Advanced
Joined: Sep 2020
Posts: 52
Likes: 3
From: kalamazoo michigan
yea i would never of used 4.10 rear if i had known i was going to end up in the power level im at...unfortunately my budget at this time is just completing the car...later i will buy a stage x 4l60 and probably a 3.42 rear and turn the boost way up
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