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| | | | Joined: Sep 2011 Posts: 2,951 'Bolter | | 'Bolter Joined: Sep 2011 Posts: 2,951 | I have the good fortune of owning 2 different T5 trannys. Now I need to pick which one to use.
I have a 1993 WC T5 with a 3.97 1st gear and a 0.72 5th gear. My rear is a 3.73. My 2nd T5 is from a Camaro and has the 2.95 1st gear and a 0.63 5th gear.
I ran some calculations online trying to figure out the final RPMs for my 250ci while cruising at 70mph. The 0.72 OD tranny calculates to just about 2200rpms at 70mph. The 0.63 gives just under 2000rpms at 70mph.
I don't want my engine to bog down on the freeway if I come to a hill.
The Camaro 0.62 OD gear has me a bit worried. Maybe I shouldn't be because the 88 Camaro that the T5 came out of had a 3.08 rear or a 3.42 rear but had a 26" tall tire. I will probably have a 29" tall tire.
Any suggestions? I already know that the 3.97 1st gear will make that first shift fairly quick. | | | | | Joined: Feb 2002 Posts: 12,029 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Feb 2002 Posts: 12,029 | I'd vote for the .72 OD
Bill | | | | | Joined: Apr 2013 Posts: 14 New Guy | | New Guy Joined: Apr 2013 Posts: 14 | I've been working with Tom Langdon to source a T5 for my 1964 C10. He had one ready from a Camaro, but it had the .63 5th gear. We decided that for my 230 engine and 3.73 gears, it would be better to wait for one with the .72 gear. Hope I didn't make a mistake! | | | | | Joined: Sep 2011 Posts: 2,951 'Bolter | | 'Bolter Joined: Sep 2011 Posts: 2,951 | The 250 I have should have good torque at low rpm's. The V8 Camaro T5s are pretty hard to find, so I think I'll install that one. It won't need the adapter plate like my other T5 from an S10. I'm still nervous about it because I'd rather not do it all over again. | | | | | Joined: Apr 2013 Posts: 14 New Guy | | New Guy Joined: Apr 2013 Posts: 14 | Yeah, it about broke my heart to pass on that transmission, and eventually I do plan to add a 250 crank to my 230. But my truck will not likely be driven at higher speeds, and I wanted to be able to use 5th gear at lower speeds. I'm hoping that I can find on from an Astro van. | | | | | Joined: Sep 2011 Posts: 2,951 'Bolter | | 'Bolter Joined: Sep 2011 Posts: 2,951 | Here are some more figures for comparison. This info is all from GM Heritage Center documents.
The 305ci V8 Camaro in 1988 had a 3.08 rear axle.
The TPI 305ci made 290 lb-ft or torque at 3200 rpms.
The EFI 305ci made 255 lb-ft of torque at 2400 rpms.
By comparison, my 1971 250ci makes 145 HP.
It has 230 lb-ft of Gross torque at 1600 rpms.
and 185 lb-ft of Net torque at 1600 rpms.
If I run 29' tires and my 3.73 rear then calculations show I'll have 1906 rpms at 70 mph and 1770 rpms at 65 mph if I'm in 5th gear (0.63). I just don't see myself driving over 70mph in this truck.
Last edited by Lugnutz; 06/13/2013 8:27 PM.
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