I have a powerglide in my rat rod. It came from a 6 cyl. so it has the 1.82 low. The truck is getting a fresh TH350. Same 1:1 high, but a 2.52 low. It wouldn't hurt to swap my rearend for one that will give me lower rpm's on the interstate, but I still want at least a slightly stronger takeoff. Anyone good at calculating what ratio would equal my 3.90 in low with the change from 1.82 to 2.52? If it helps, I have 30" tires.
Something in the mid 3s would probably be good. I understand what you're wanting to do, but in real life it works out better if you just pick the rearend ratio you want based on rpm at some highway speed, but taking into consideration how much acceleration you'll get too. So go for something like 3.5x, maybe down to 3.2x
Looks like 2.82 will give you the same overall low gear to me, but a little lower than that sure wouldn't hurt acceleration. Larry T
That's what I got, too: 1.82*3.90=7.098, so 2.52*x=7.098 or 7.098/2.52=x=2.817. Sorry, I'm kind of a nerd. Hey wait a second, what kind of car did you say that was? :0])
You can't have it both ways... Both transmissions are obviously 1:1 in top, so the same axle ratio will give you the same cruise RPM no matter what. The deeper low gear should help takeoff. Here's the formula: New axle ratio= old gear (1.81) / new gear (2.52) X old axle ratio. 2.80, just like Larry said. I don't think I'd go that far down though... That's almost a 25% drop in RPM in top.
While we are on this subject, I am planning to run a T5 out of a V6 firebird behind a '54 model 235 from a truck, in my roadster. A 3:73 rearend out of a mustang, and a 29" rear tire. What numbers should I be looking at for the bottom and top? I have a Clifford 4 barrel intake, and a set of Fenton cast headers, and possibly a McGurk 3/4 race cam to run as a combination. Thoughts, comments, critisisms, concerns? TIA...
Oh man, you're wanting answers that require actual knowledge about cars, sorry man. But never fear, this is the HAMB! Someone will know (just not me).
I think he said it was a beater or a jalopy. Surley to gawd he didn't use the R word on this site. Sorry my head hurts and I'm not up to math today. But a 3.26 to 3.55 gear should give you a fair hole shot and still be drivable on the highway.
With your 30 inch tires, the gear ratio gives the engine speed at 90 mph. So, your existing 3.90 gear needs 2600 at 60 mph. I ran my roadster with a 3.00 gear for a long time, and it was a good combination. With a six, I think the advice to go with 3.20-3.50 gears is spot on.
3.08's are a dime a dozen, go with that and you will have a better start ratio. One other thing, don't forget stall ratios. Powerglide might have less stall ratio than the 350 does. So you might even be able to go with a 2.73 and still have decent go from a dead stop.
Thanks for all the help! My '36 Chevy pickup is getting a rebuilt 350 along with a TH350. Replacing a tired 350 and PG. The powerglide came from an old El Camino that had a 6 in it - often preferred by swappers becase 1st is a little bit lower. Is the "R" word considered bad on H.A.M.B.? What is the current PC term? "Unfinished-American"? I'll have to look up stall speed. Never heard of it as a consideration, or any difference in it between PG and Turbo. I'm running a stock converter in both. I had no idea I could go to such a high ratio! I was wondering if I was going too far with a 3:42! I love to drive my old truck and have been hitting events further and further away. Almost ashamed to say that I want a bit better gas mileage on long stretches of interstate, but that's reality for ya. I will be shopping for an S-10 rear now because that matches the desired width. Any others that size? I haven't even checked the newer S-10's, are they wider? It would be nice to have 4 wheel discs, hope to find a posi also.
Converters look similar but could be different inside. Aside from that you may want to consider a 700r4 or 2004r overdrive transmission if you want to go to a 3.42 axle ratio. Those will provide you with a nice cruising top gear. The 2004r I believe will fit in place of the PG or TH350 without too much of a headache. You can probably even use the PG TV rod for the 2004r or 700r4
I was at one time considering a manual and searched T5. There were several good sites that told ratios depending on WC or not, what vehicle they were originally in.
Yes. Grab the shift lever. Low gear on your T5 would be all the way to the left, then towards the dash.
Ebbspeed, good answer! for ratios, try here: http://www.britishv8.org/Articles/Borg-Warner-T5-ID-Tags.htm That's the number on the tag, not the casting. Ralph
Scored a 3.07 third member Friday, ought to drop me around 600 rpm on the interstate and get some use out of 1st and 2nd.
The Jalopy Journal
