View Full Version : Trani advice for a 373 rear
Iceboat-Bob
06-17-2021, 07:58 AM
I'm starting to look at standard trani options for my build... MK4 with a 347 stroker and a 373 rear straight axle, 15" halibrands w/ billboards. Aiming for a car show weekend cruiser with some punch. Any advice?
CobraboyDR
06-17-2021, 08:13 AM
.64 OD, and you will have a nice slab cruiser that will kick a$$ between stoplights.
GoDadGo
06-17-2021, 08:21 AM
I'm running 3.73's in my car and it works well with my set-up.
You should be turning 2,200 RPM @ 71.01 MPH with the .64 O.D.
The numbers I ran were with a 25.9" tall tire.
edwardb
06-17-2021, 10:00 AM
You need to factor the transmission into that before reaching any conclusion. With a TKO/TKX, 3.73 might be a little short. 3.55 is the most common by far. But 3.73 works if you're OK with running out of 1st pretty quickly and slightly higher RPM cruising. You can evaluate difference combinations with a calculator like this one: https://www.tremec.com/calculadora.php. Interesting to see they updated the calculator with the new TKX options. Nice.
I am running a TKO500, 351W, with 373 IRS rear end. It winds very quickly and is super fun. I think the 373 wakes up the motor. What it really needs is a 7k redline!
It works well for my use, but if I was driving it everyday I might go with a 355 rear end.
Jeff Kleiner
06-17-2021, 10:59 AM
If you use the TKX model TCET17765 with the 2.87 first gear and .68 fifth gear you'll be in a good range on both ends. With your 3.73 rear end the TCET18086's 3.27 first is too low as is the TCET18084's .81 fifth gear. Just my opinion of course ;)
Jeff
Sdonnel
06-17-2021, 12:09 PM
Like Jeff said, that combo is a good one. That's what's in my car right now (and it's at Jeff's place for paint). The 351 makes plenty of torque and will keep the tires moving as much as you want.
Scott
Iceboat-Bob
06-17-2021, 03:55 PM
Thanks for the calculator link, that's great.
Iceboat-Bob
06-17-2021, 04:01 PM
Thanks Jeff, I ran that through the Tremec Calculator and that looks like the ticket. Thanks for the model number.
OVCobra
06-17-2021, 04:15 PM
Iceboat
I am running pretty much where you are headed (347/3.73 with 315/35/17's), continue to use a Z spec T5 with 2.95 first and 0.63 OD. Plenty (too much?) torque in 1st gear so would not want any deeper 1st. 0.63 OD gives easy highway cruising so very pleased with overall package.
T5 has stood up so far but traction limited with street tires.
Depending on projected power from your 347 may want to step up to the TKX geared as Jeff suggests.