5 or 6 speed auto transmission Conversion?

[98_k1500]

Torque converter not locking would explain the difference.

 

[Big D]

Don't you have 35's and 4.10s? What's your rpm at 80?

 

[Big D]

You must be registered for see images attach

 

[98_k1500]

I do. I'll check it some time. IDK that i have ever done 80 in it lol. I also have a 5 speed, the OD ratio may not be the same. When you are cruising, if you touch your brake does the TC unlock? My speedo is not corrected, my truck has factory 4.10s so i'll have to do some math to see exactly how fast 80 is.

 

[98_k1500]

You will need to see my tach when my speedo is on 74 mph. The truck will actually be doing 79.7 mph. Close enough? As a side note, not many 5 or 6 speed autos are double overdrive, there is just less spacing between the gears, so while in theory, this will help, if your final drive ratio is the same, it will not affect your cruising rpm. The trans in the link still runs a .75 OD, so it is not going to help the issue at hand without also re-gearing.

 

[someotherguy]

I also have a 5 speed, the OD ratio may not be the same.

700R4/4L60/4L60E 0.696:1
4L80E 0.75:1
NV3500/NV4500 0.73:1

Richard

 

[Crash]

Something is off, like the torque converter not locking (like what was said already) or you have more gear than you think.
Check this out.
http://www.teammfactory.com/gearcal...annytype=&tranny=Calculate+Transmission+1+&+2

 

[98_k1500]

700R4/4L60/4L60E 0.696:1
4L80E 0.75:1
NV3500/NV4500 0.73:1

Richard

Should be close enough to not matter. The tach needle is 100 rpm wide on these trucks anyway. Its not like its that accurate lol

 

[Crash]

Or try this one.
http://tri-5.chevyrides.com/rpm.php

 

[sewlow]

Turbo 400 with a Gear Vendors over/under drive. Tadaaahh! 6 speeds & the final drive rpm's would drop down to a more mileage friendly zone. IIRC the final drive with the O/D is .69.
Not sure if the G/V will bolt up to a 4L60/80 though, but that would give you double over drive, & 8 speeds!