Am I slipping?

[TType85]

I'm trying to find out if this is even a problem. The car is a non-posi car with a 9" Art Carr 3500 Stall NL converter running on 275-50-15 Nitto DRs (25.75" tall).

I took the car out to the 1/8 mile track a week ago. At 17psi the car ran 7.9@92mph 2.0 60'. At 20psi the car ran the same 7.9@92 with a 2.0 60'. No spinning off the line. Less knock than the 17psi run.

Now heres the problem. According to Direct Scan I am turning 5200rpm at 90mph on all the runs. Using the calculator on [link]http://www.prestage.com/carmath/calc_Gears.asp[/link] I am showing that if there were 0% slippage I have a rear end ratio of 4.43. At 4925rpm at 75mph this show 5.03!

Now I know the Art Carr converter will have some slippage, but that much? Is my tranny slipping bad?

Here is the data from MPH/RPM Data from DS in 3rd gear.

MPH         RPM
71	5550
72	5225
72	5100
72	5050
72	5075
73	4950
73	4950
74	4950
75	4925
75	4975
76	5000
76	4900
77	4900
77	4900
78	4900
78	4950
79	4975
79	4975
80	4925
80	4925
80	4950
81	4950
81	5075
82	4975
82	5000
82	4975
82	5100
83	5125
83	5050
84	5050
85	5125
85	5075
85	5050
85	5100
85	5175
85	5100
86	5125
86	5175
87	5125
87	5125
88	5200
89	5150
89	5150
90	5200
90	5175
90	5175
90	5150

Any ideas?

BTW: Posi goes in tomorrow morning!

 

[WE4]

That big of turbo and housing will blow through an AC 9" . Have Art tighten the top only... Big difference I guarentee.

I would almost bet it has trouble getting up to spool then once spooled gets real loose>

 

[TType85]

Thanks for responding Bruce!

The wierd thing is the car spools GREAT.

I can get 3100rpm at 0psi and I can get 5+psi on the brakes real quick. from a roll, on a downshift its almost instant boost.

I wouldnt dbout that it could be the converter though. Who knows the quality of the Art Carr products floating around.

I have been really thinking of going to somthing like the 9/11, but I want to make sure that i'm fixing the problem, not just throwing $$ at it.

 

[WE4]

Originally posted by TType85
Thanks for responding Bruce!

The wierd thing is the car spools GREAT.

I can get 3100rpm at 0psi and I can get 5+psi on the brakes real quick. from a roll, on a downshift its almost instant boost.

I wouldnt dbout that it could be the converter though. Who knows the quality of the Art Carr products floating around.

I have been really thinking of going to somthing like the 9/11, but I want to make sure that i'm fixing the problem, not just throwing $$ at it.

WAYYYYYYYYYY too loose... That is your problem or one of them anyway.
Bruce
WE4

 

[TType85]

small update:

Looking at the dipstick I found a good amount of clutch material ON the dipstic..... time to do a tranny service and see whats going on