Too much converter slippage?

[nevdos]

Im thinking i may have too much converter slippage going on
8-in unit goes 5550ish-5600rpm on the brake

Specs are
4.30 gear
28 in slick stiff sidewall m/t
7800-7850 rpm in lights
133.5 mph

If i figure it out correctly im getting over 12% slippage
A buddys car goes identical mph in the 1/8 and 1/4 but only goes through lights at 7300-7400 rpm
We have same gears,tire size ,brand ,,,etc,etc
In fact his car goes 5900 on the brake and 60fts about .05 better than me (1.32 average*best of 1.29* in his car - and 1.38 best in mine, so i know his works well
It seems like the car just didnt pick up in better air like i thought it would and im wondering if this is why?
Trans fluid look and smells ok-th400 trans
Thanks
__________________

[af2]

Both with the 400??

[Alan Roehrich]

Yes, 12% slippage is too much. It is likely that your converter is inefficient and does not multiply torque well, leading to a slower 60' and a higher RPM for a relatively equal MPH with the same gearing and tire size. Most of my converters are around 4-6% and flash between 5800 and 6400. I use and sell ATI torque converters.

[nevdos]

both cars have th400s
in fact i have his old trans i my car lol
he sold it to me to buy a trick piece, and when it didnt work ,he had the same shop who built mine do another one for him
i called ati today as thats who originally built it '
it was made for a different combo and when i told him what its behind now, he laughed, and said lets get it back and cut it open and see if its not hurt
im pretty sure its way off for the new combo so well see what they say when they see

[hsutton]

Nevdos, that is a bias ply tire and will grow by appx. 1/2" in addition to it having a 28" diameter to start with. My Moroso shows the "no slip" rpm to be about 6750 rpm at 133.5 mph. Yours has to be slipping somewhere in the vicinity of 1100 rpm at the 1/4 mile mark. The converter definately needs to be looked at.

[Transman]

Agreed, you need to look at things as that's a bit much for slippage. Although many put too much worry into slippage percentages. There are some awfully fast cars out there with 8% or even a tad more slippage. It's all in the combination.