What speed will our cars upshift from 3/4 at WOT?

[Mustang 1]

Good afternoon to all! Just a quick question. On a 1987 GN with the stock gears and oem tires and an Art Carr 2800 stall lock-up converter at approx what speed will the 3 - 4 upshift occur? I only have an 85mph speedo which is pegged long before that. The cars has ran 96 mph in the 1/8th mile but I don't know about the quarter. The car is modifed with a pte 52,cas v-4,oo9's,3"dp,3" exhaust,etc. 21 psi of boost at this time with 23 degrees of timing. Using an 1/8th mile horsepower with the total weight of myself and a loaded GN figured at 3700lbs and a drivetrain loss of 15% that come out to like 440 horsepower a the rear wheels. The reason that I am wondering is I took my boss for a ride and scared the s#*! out of him! He is a Mopa collecter and has had several Hemi's and 440 6pk cars and said my car is the fastest car that he has ever been in. I thought that was a pretty cool compliment coming from a guy with a 440/6pk Plymouth Superbird in his garage! I then let him drive it and now he wants to buy it! Well, anyway, I was just wondering as my car has a top speed limiter built into the prom but it is 155mph, which I did not hit. I was in 4th at WOT for like 20 seconds or so, felt like 135mph to 140. Does anyone have a conversion chart and can figure an approximation for me? All help is greatly appreciated!

 

[BoostKillsStres]

Depending on what rpm your car is shifting form 3-4 at, mine was right around 106 at 5200 w/ the converter unlocked so figure somewhere around 103-106 at the shift and probably closer to 103 since the car will probably shift at 5000 or just a little lower if you leave it in OD.

HTH

 

[Gary Wells]

FWIW & IMHO:
I think that you are seriously underrating the rear wheel horse power loss in an automatic. Generally, I think that standard transmission cars lose about 12%-14% where autotrannies generally lose as much as about 23%. On www.CorvetteForum.com under Z06 column, they seem to lose about 12% for the ones that check before and after, and the Z06 are all autos. It seems to me that non-automatics lose a little more.

 

[GNVAIR]

Originally posted by Wells
FWIW & IMHO:
I think that you are seriously underrating the rear wheel horse power loss in an automatic. Generally, I think that standard transmission cars lose about 12%-14% where autotrannies generally lose as much as about 23%. On www.CorvetteForum.com under Z06 column, they seem to lose about 12% for the ones that check before and after, and the Z06 are all autos. It seems to me that non-automatics lose a little more.

All Z06 Corvettes are 6 speeds, unless GM changed them this year. Not to bust stones or flame. Just making a slight correction.

 

[gn85]

I know my car usually hits that shift around the same... 105 or so. Actually gives a nice little shove when that shift comes too... surprisingly.

Congrats on getting another person hooked on the turbo.

 

[Gary Wells]

OOps:
GNVAIR:
Thanks for the correction. Evidently I did not proof read that.
Embarrassing. And to think that I own one, too.
I did that at work while everybody is looking over my shoulder.
If I correct it, it's like I am trying to make it seem as if there was never an error there, so I guess I will just leave it.
Freudian slip, maybe. I wish that the Z06 did come out with an auto. And I wish that mine was that way.