3.55 vs 3.08 rear gears??? and how dificult of a swap is it?
11-14-2016, 10:36 AM
#41
Melting Slicks
I think he means back before trucks commonly had V8s, they usually had low(high numerical) gears to make up for lack of power.
Last edited by Richard Daugird; 11-14-2016 at 10:36 AM.
05-23-2018, 02:03 PM
#42
1st Gear
Member Since: May 2018
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I agree. I had 3.08 in my 63 impala ss conv. With 350 268 comp cam. And had rear end rebuilt. I was told 3.08 gears were not available. And was talked in to 3.55 gears. With a street strip power glide. Tired of getting passed on the freeway. There’s so many combinations. Od trans. Or 3.08 s ?
07-04-2022, 09:37 PM
#45
Old Pro Solo Guy
There are so many ways to accomplish what you want. Here is a spreadsheet I built to let everyone play with gear ratios and trannys.
The real problem was the old close-ratio trannys only had a 2.2 gear spread between 1st and top gear. That meant a 3:55 was a good all-around compromise gear. But the OD trannys can go to as high as 6.0 gear spread. That means you can have the best of both worlds, great acceleration and comfortable low rpm cruising.
My 72 BB had a very low 7.2 to 1 overall in 1st gear. Horrible combo, 2,20 box and 3.36 rear. Feels like you are starting in 2nd gear and revs to 60+mph in first. Cruises fine though.
My LT-1 had both a CR/4.11 and a WR/3.55 in it at different times and both were great in town. 9 to1 overall, it's about the minimum to feel "good" off the line. But only the 3:55s felt tolerable on the highway. 60mph was a comfortable cruise with a free-revving LT-1 at 2700 at 60, 3200 at 70. But even with that gear at 70+ the oil tended to heat up after a 5-10 min and the oil psi would drop, and all I was trying to do was to keep up with traffic! So it was tolerable on the highway but not ideal.
My current build will have both a 10:1 off the line and a 2200 rpm cruise at 70mph with a CR TKX OD, and a 3.36. But it will take the 4.2 gear spread of a TKX to do that.
The real problem was the old close-ratio trannys only had a 2.2 gear spread between 1st and top gear. That meant a 3:55 was a good all-around compromise gear. But the OD trannys can go to as high as 6.0 gear spread. That means you can have the best of both worlds, great acceleration and comfortable low rpm cruising.
My 72 BB had a very low 7.2 to 1 overall in 1st gear. Horrible combo, 2,20 box and 3.36 rear. Feels like you are starting in 2nd gear and revs to 60+mph in first. Cruises fine though.
My LT-1 had both a CR/4.11 and a WR/3.55 in it at different times and both were great in town. 9 to1 overall, it's about the minimum to feel "good" off the line. But only the 3:55s felt tolerable on the highway. 60mph was a comfortable cruise with a free-revving LT-1 at 2700 at 60, 3200 at 70. But even with that gear at 70+ the oil tended to heat up after a 5-10 min and the oil psi would drop, and all I was trying to do was to keep up with traffic! So it was tolerable on the highway but not ideal.
My current build will have both a 10:1 off the line and a 2200 rpm cruise at 70mph with a CR TKX OD, and a 3.36. But it will take the 4.2 gear spread of a TKX to do that.
Last edited by leigh1322; 07-04-2022 at 10:03 PM.
07-05-2022, 12:32 PM
#46
Instructor
gear ratios
on my 1970 big block restomod I am keeping the 3.08 first gear but going with the wide ratio TKX. it has a 3.27 first gear which will give it 4.11 type off the line acceleration but a nice cruise rpm in OD. Silver Sport recommended this set up and it gives you that preferable 10.0 ratio off the line.
07-05-2022, 01:05 PM
#47
Tech Contributor
This thread is 10 years old. Back then you could get good parts like the US Gears Tom's sold. Tom was alive, his best spiders were still made, Timken bearings were common and usa made, prices were lower on everything.
10 years later the theory still applies, TKOs are gone and so are many people and those good parts.
10 years later the theory still applies, TKOs are gone and so are many people and those good parts.
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aaroncorvette (07-09-2023)
07-05-2022, 01:27 PM
#48
Old Pro Solo Guy
aargh!!!!
"'Related Threads" strikes again!
"'Related Threads" strikes again!
07-05-2022, 02:41 PM
#49
Le Mans Master
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RowdyMT (07-09-2022)
10-19-2023, 02:23 PM
#50
If you have a 4 speed...from your rear gears to 370 gears will feel like 75HP difference. I have a 5 speed Tremec 600 and just drove home from 370's to 411 rear gears. The car feels like it explodes anywhere near the peak BP 383 4,300rpm TQ band. 3rd gear pulls like 2nd. 4th gear pulls like 3rd . My timing is all in at 2900rpm and 3rd/4th are amazing with a push back in your seat with just a push of the throttle anywhere ...everywhere above 2800rpm. GEARS.
