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which gear set

  • 3.23

    Votes: 7 6.0%
  • 3.36

    Votes: 7 6.0%
  • 3.42

    Votes: 30 25.9%
  • 3.55

    Votes: 28 24.1%
  • 3.73

    Votes: 44 37.9%

Which gears to go with

15K views 53 replies 34 participants last post by  65cayne 
#1 ·
Well I posted up bout trans a while back and after alot of trying to come up with the funds for a 200r4 or a 700r4 its just not in the cards at the moment. Maybe down the line it will be something for me to consider but its just not feasible right now. Besides even if I could get together the money for a built 700 or 200 id still need my gears and stall which would definitely not happen. Id have to use some POS crap stall to get me by til I could afford a good one to match my combo. Then add in the extra parts needed new speedo connector thinga ma bob, new 200 or 700 dipstick tube, lock up wiring kit, T V cable, shorten the driveshaft (if I went the 700 way) and relocating the rear trans mount and shipping just kept adding up. I found a few great companies like extremetrans tht I could get it all for round 2100 plus 150 shipping, or jakesperformance which was round 2250.00 for just trans plus shipping, and then davids was round 2345.00 and then shipping plus all the lil add ons as well. These all didnt include a torque converter tht was trans alone. Then add on gears all the nick knacks and such and i was closing in on over 4000.00 for everything good stall, trans, all the trans goodies, cooler, rear end bearing kit, posi unit, and good gear set.

So since I have a brand new built turbo 350 tht cuts tht cost right there, I was gunna get a very nice PTC converter from a nice guy on here but after calling Tim and chatting he said it wouldnt be the best for my application. But he said he would build me a great 9.5/11 inch dont know how to explain it he said its the best of both worlds looks like a 9.5 inch but its an 11 or something he said something about the vanes being set up for heavy cars and it flash stalls to 2800 rpms but driving around town i wouldnt even know it was in there and its double balloon this and that I dont speak converter. Most my cars have always been stick so not much experience with em. He said in his opinion it would be the best of both worlds since this is a daily driven car. Not to mention the price was amazing for a built converter for my app less than what I was about to spend at edge or for the used one so couldnt argue much so I ordered it.

Now onto the last step since I have made the decision to go built TH350 and what converter to use. I am ordering a posi unit with it but need to know what rear gears would be great for me.

Heres what the car will be used for daily driving with some freeway not a whole lot no big cross country trips planned. The car has 28 inch tall tires on it and tht wont change even the new ones coming for the ralley rims are 28 inches tall. Want something tht feels nice and solid and fun to drive as well tht can hold its own and surprise a few people lol

Its a 1970 chevy impala weighs round 3890 pounds with a built 355, afr heads, jones custom hyd roller 228/228 576 1.6 intake/ 512 1.5 exhaust 108 lobe sep, 105 in center 111 ex center. 680 quick fuel VS carb, 1 5/8s long tubes and 2.5 dual exhaust
 
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#2 ·
I was debating same thing when I decided to switch from the 8.5 10 bolt to the 9in mine got solved for me as cost was a big factor I went from 3.42 to a 3.70 only cause that was what came with the rear. I had been looking at 3.50 for the 9 in and that is what I figured would be a good compromise till I get a 2004r myself. I have a th350 now.
 
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#3 ·
Figure the highway RPM that is tolerable and install that gearset. With the 350, I was going with 3.08/3.07. With the 2004R on order, I'm going with 3.73. Should give me ~2000RPM @ 60 MPH.

RPM=MPHxDiff gearx336/tire diameter
 
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#5 ·
Figure the highway RPM that is tolerable and install that gearset.

RPM=MPHxDiff gearx336/tire diameter
That is true.
I know mine was running 3000 rpm at 65mph with 2400 stall and basically stock th350 with the 3.42 gears.
 
#6 ·
He said with the converter I am going with tht any gear between 323 and 3.55 would be negligiable in its effect on the converter I told him I hadnt bought the gears yet and didnt know which but id know within a couple days and he said to just call him and let him know they are round a week out from having it ready an cant start it for 3 days hence why im asking u guys now lol
 
#8 ·
I called and talked to Tim at PTC to get his views on gears an with my combo and useage. An he said quite frankly the performance differences from a 3.23 and a 3.55 are very slim and would be hardly noticable but the rpms on freeway would be more of a noticable thing and he said a nice 3.36 would be good as would a 3.42 and would probably go with whichever he found the best price on.

3.36 gears equal 2822 rpms

3.42 gears equal 2872 rpms
 
#20 ·
===============

I agree,3:42's are his best all arround comprimise for perf vs tollarable cruise rpm with the old school non od TH350 trans and tire height he's running.

But when talking gear rec sometimes you have to say enough is enough and going with 3:55s or more gear in this case gets into too much rpm at cruise IMHO.

And cruise rpm is even more of an issue if he plans on going mostly open road crusing and not mostly strip use which are to different animals when you have non od non lockup converter trans to deal with like this guy is.

Also dont forget that as far as i am aware of the rpm vs speed calc doesnt take into acct old school auto trans that may have a bit of slippage with stock non lockup coverter and even more slippage with a non lockup perf converter.

So if he's running a perf converter in his non od H350 trans he needs to add a min of 250-300rpm (or more) for a looser non lockup perf converter to get a more accurate cruise rpm estimate.

BTW,a few of the rpm vs road speed estimates i see posted here are a bit low unless maybe they are running very tall 29-30" tires which they didnt state was the case or not.

Scott
 
#11 ·
Chris..with the limited track time and over all cruising in mind I would opt for the 3.55 gear and I`m teetering on wether the 3.73 would actually be better.
That`s a portly little car you got there and every bit counts.

BigRed is a little on the hefty side too and I have 4.10`s
Tim at PTC, as does the rest there, knows what`s up...GOOD CHOICE :thumbsup:
 
#13 ·
with 3.73:1 rear gear ratio and a 28" tall rear tire height, you'll be reving at about 3,150 RPM at 70 MPH which isn't too bad for a car that won't see any interstate travel, and that would be a good gear ratio for the camshaft you have. 3.55 gears wouldn't be a bad choice either, and you'll rev at about 3,000 RPM at 70MPH with them.

http://www.richmondgear.com/index.php/gear-transmission-calculators
 
#14 ·
If you plan to OD later....3.73 is the MINIMUM, you do not have a computer-controlled engine that would like lugging at 1500 rpms

some thoughts
I ran 3.42 in my 454 Elky for years w/3000 B&M converter, little different power to weight ratio here. Cruise was 2700 at 65ish. The 454 and 3000 stall was plenty to get my #3995 race weight car solidly into the 11s

am sure with you in you 70 IMP, you push 4000# too. Less engine, lots less torque....err to the side of MORE GEAR if perf is important to you more than cruising.
 
#15 ·
An thts true and want the best of both worlds I weigh 236 in off season with a 8 to 10% bodyfat ( I bodybuild keeps me busy lol ) on season I get down to 4 to 5% bodyfat and trim down to 215. An I have done some weight removal on the car to the tune of 250 pounds and have about 250 more ill be removing all without changing the appearance and such. When i got it with AC and all it weighed in at 3942 pounds as it sat. Its now round 3890 with me in it.

I am thinking overdrive in the future but also a 12 bolt as well when I do so maybe just some cheap gears for now hummmmmmm decisions
 
#16 ·
My 68 Camaro ragtop project came with the fearsome 327 2 bbl, junk heads standard. Backing this was the Powerslide and a 10-bolt with whopping 2.73 gears. Moderate weight so she was still fairly peppy even thought the cam was later found with a few nearly flat lobes.
Beefed the 327, went to 2004R, and the 10-bolt yielded to a 12 bolt. Went with 3.73.
with the 2.78 1st gear in the 2004R she will launch like a th350 and 4.00 gearing and will cruise like 2.50 gearing. This is a 'road' car so figuring cruise at 65-68 vs 60mph.
 
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#18 ·
With 3.73:1 and 28" tire

1st@ 6200 rpm = 55mph
2nd@ 6115 rpm = 90mph
3rd@ 2459 rpm = 55mph
@ 2906 rpm = 65mph
@ 3353 rpm = 75mph
@ 6147 rpm = 137.5mph

I like 3.73:1 - good all around street gear and as said previously, If you go with OD trans, you will want nothing lower numerically IMO.
 
#19 ·
My car used to have a 700r4, 4.10gears and 28" tires and would cruise 70mph at apx. 2350 with converter locked in OD, also the 3.08 first gear and the 4.10s will get ya moving quick and easy:yes:
 
#21 ·
This is all a matter of preference. you're going to get bazillion different answers and various viewpoints on this, so here's mine: I had a 475 HP pump gas 4,200 LB 4 door daily driver for over 3 years with an automatic overdrive trans and I installed 4.56 gears in the rear and I loved it like that. With 28" tall rear tires it reved at 2,750 RPM at 70 MPH and I drove that car every single day on the highway to work and back even in the snow with snow tires.

I also had an old Vette with a Muncie 4 speed trans (obviously there wasn't an overdrive in that) with 3.73 rear gears and 26.5" tall rear tires and drove that to work 3 days out of every week for 8 months out of the year for 6 years and I loved driving that car too. It reved at 3,200 RPM at 70 MPH and it was fine.
 
#26 · (Edited)
==============================

Guys,your completely overlooking the fact " the origianl poster of this thread " said he'd like to go with an auto OD trans " but cant due to lack of funds " .

Thats why he stated he's going to stay with the " NON OD 350TH TRANS " he currently has so all the reff for best gearing for auto OD trans most of you guys are reffering to in this thread if completely off target for his non od TH350 auto trans app.

Thats why i rec 3:42 gear max with a non od TH350 trans as an all arround good gear for his setup to have a " REASONABLE CRUISE RPM VS DECENT PERF " for his mostly steet app that will see little to no non competitive strip use as he said the car will see. (With taller 28" tires 3.55's max)

But if he's running a non lockup perf converter that will increase cruise rpm by 200+ rpm over a tighter stock converter and if thats the case he'd be better off going with good used and or nos 3.31's or 3.36 gearing (depending on if he's running 12bolt or 10bolt rear) would be a better choice with perf converter. (with taller 28" tires 3:42's max)

Rememebr,this is a car that will see little to no non competitive strip use being a mostly all street /open road cruise app thats not looking for every possible ounce of perf out of the car at all times.

Thats not what he's looking for here like you can get when your running an OD auto trans which isnt the case here with his non od TH350 auto trans.

BTW,the mult chevelle's/GM muscle cars i dealt with/worked on over the yrs with muncie trans and 3.73's (with with known proper speedo gear-s in trans) & approx 26"-26.5" tall tires turned 2,950-3k rpm @ 60mph & 3,350-3,400rpm @ 70mph. (+ -approx 50rpm )

So the 3,200rpm @ 70mph with 3.73's & 26.5" tires your reffering to here is a bit low from my exp with that setup in many diff man trans cars/apps over the yrs.

With your vette you may have had 1 or more of the following items collectively a bit off which is very common with these cars like for example the speedo gear in the trans wasnt correct for 3:73's , your speedo was not reading accurate,tach was not reading correct or maybe you were told you vette had 3;73's in it wher you bought it when in it fact had #;42 or 3:55's in the rear & not 3:73's which is somehing i have run into 1st hand with other peoples cars.

Just last yr i had a friend that swore his 70 ss 396 chevelle has 3:73's in it because prior owner stated that was the case and even though the casting id on the rear end hosuing showed it was born with stated 3:31's he belived the prior owners statement it had 3:73's &bought used 3:31's install in rear end to reduce cruise rpm.

When he took car to shop to have the 3:31's installed they assumed the guy knew what he had in the car for gear so they didnt verify what ring & pinion was currently in the car prioer to removing them and guess what?

After removnng the ring & pinion they counted the teth and also verified GM PT that they were in fact 3:31's to begin with and found there was improper speedo gear-s in the man trans causing improper speed vs rpm cruise reading.

So point is ya never know unitll you chk to verify things are correct when talking speed vs rpm reading with these old classic muscle cars that have many variables that may have been changed over the yrs that can collectively cause inaccurate speedo vs cruise rpm readings.

The current setup in my chevelle (3:31's/M20/26.25" tires) along with verified proper for 3:31 ring & pinon driver & driven speedo gears i personally installed in the trans turns approx 3k rpm at 70mph.

Note: Even though i ensured i had the above correct/accurate to ensure i was getting accurate speed & rpm readings I also used a GPS to verify speedo was reading accruately (which was the case) and i also used my stand alone Snapon engine analyzer/dwell guage to verify tach is reading correctly (which was also the case too) .

So by doing all the above that ensured the 3k rpm & 70mph reading i am seeing in my chevelle with 3:31's , M20 ,26.25" tires is accruate.

So with signifciantly more gear (3:73's) in the vette only running 200rpm more rpm then 3:31s at same speed/70mph both being man trans with bearly begliable .25" (1/4") diff in tire height that may equate to a 50-100rpm delta shows something was not right with the speedo , speedo gear setup,or tach in trans that showed only 3,200rpm @ 70mph which should have been closer to & or approx 3,350-3,400rpm + - few rpm.

Scott
 
#25 ·
If these gears will stay when you finally get the OD (hopefully the 200-4r) then I would go 3.73 or better yet 4.11 which is what I have. its the best of both worlds.
 
#27 ·
Hey Scott thanks for tht I was just about to come in and say the same thing lol so heres whats going on

I have my new built th350 in my car now and it was built using advice posted up by jake from Jakestransmissins where he told someone online how to properly setup a good th350 tht can handle bout 600hp. Should do great behind my lil sbc, it has all the strong upgrades I could think of, and I had a good friend tht wks for TSO trans build it for me. He had a hardened sprag i heard tht always breaks, trans go shift kit, used the best clutches available and added some extra clutches (he said theres now 5 in first 4 and then 3 for reverse or something like tht I dont speak automatic trans I dont know how many there are stock or what he meant lol), and he did other things tht he knew to add to the build for a stronger trans and followed jakes advice on the net I was there while he built it and only cost me 500.00, good to have good friends. I also added a trans cooler largest i could fine and a PTC custom 2800 stall converter. I also filled it with type F fluid as per many peoples advice as they say its a much better fluid to use in the TH350. So far its great now I just need to change the pathetic 2.56 rear gears I have

I have a 8.2 10 bolt rear end and dont plan on going 12 anytime soon no need, but I will be adding moser axles, a good posi unit and new gears with a full rebuild kit. I have seen tht they dont make a 3.42 for the 8.2 so tht ratio is out now I have the option of going with either a

3.36 or a 3.55 ratio i mainly do around town driving to work which is few miles away and to the gym. I do some freeway but not a huge amount and like i said the rear tires are 28 inches currently and the new tires and rallys measure the same just wider 275/60/15 rears and 255/60/15 fronts. Current tires are 215/75/15 snow tires all around.
 
#28 ·
==================================

With your aftermarket non lockup 2800stall that will add/increase cruise rpm a bit i'd definately go with the 3:36's for sure!

But be advised that 3:55's and looser 2800 perf converter your trans has the cruise rpm at 60mph or higher speeds of 65-70mph on open road /interstate will be enough to be in the uncomfortable range some people.

People often overlook the fact perf stall coverters add to cruise rpm so when you choosing gear thats already on egde for too much rpm at cruise speed with stock tight and or lockup converter or with man trans that dont slip cruise rpm becomes an issue with a loose perf converter that adds more rpm at cruise.

Thats why i rec 3:36 gear as a max that with your looser converter would end up closer to what 3:55's would be with a tighter stock or lockup perf converter or man trans setup with no slippage.

So for example,cruise rpm with 3:55's & loose coverter would = approx 3:73s with a tighter stock /lockupo perf converter or man trans will no slippage.

See what i am getting at?

Good luck.

Scott
 
#30 ·
I have a non-OD trans and 28" tires and it spins a little over 3000rpm at 70 on the highway. I really love the 3.55 gears for a street/strip compromise w/o an OD trans. I also have a PTC 3500 stall 10" converter, that drives great at part throttle once it is warmed up and almost feels normal. I have some low-end torque I could give up (no street traction), but I was concerned about cruising with the converter slipping all the time if I used a lower-gear. I'm not sure if this is a real concern or not, but if it is real, I would be careful about gearing too low.

I think you mentioned you liked the 28" tires and weren't going to change them. I'd make real sure this is the route you want to take before picking gears/converter.
 
#31 ·
well the converter is an 11 inch custom and is a 2800 stall and its already in the car and like yours feels stock under normal driving. I already have new 215/75/15 tires for winter new and i already bought the 275/60/15 for the car for summer fall and spring and they too are 28 inches tall. So i will not be changing tires even my slicks are 28 inches tall so no worries with tht either. Only thing to determine now is rear gears which im really on the edge of 3.36 or 3.55 with my limited freeway usage Im really thinking the 3.55 would be the best way to go and give me great round town and track useage and if 3k is bout where id be with them i could totally live with tht. My old LSX camaro with a built 560 rwhp LS7 and six speed inc 6 speed had 4.56s and i drove tht daily and would drive it too wendover to race 2 hours away and in 6th it was going 3k rpms at 80-85 and never bothered me and that car was a loud beast dual 3 inch exhaust out magnaflow mufflers 2in primary headers 254/268 at 630/640 0n a 111 .050 speced custom cam. Man I miss tht car shoulda never sold it
 
#32 ·
==========

Well its a lot diff story dealing with 3k rpm at 80-85mph cruise speed in your old camaro then with your current car thats got a looser perf converter with non od auto trans & 3:55's with & 28" tires would be a considerably slower cruise speed at the same 3k rpm being roughly 65mph (+ - few mph) with the looser then stock perf converter your running adding 200rpm + - to cruise rpm.

3:36's are still my choice for best comprimise between reasonable cruise rpm and decent track perf too since your car will be seeing primarily street use and with little non competitive strip use.

Too bad 3:42's arent avail for your 10 bolt because they would be a very good choice for perf vs reasonable cruise rpm.

There isnt that much diff between 3.36's and 3.42s being kind of a wash cruise rpm wise,but there will be a more noticeable diff between 3.36's & 3.55's when talking cruise rpm.

The question you need to ask yourself is do you think you will benefit more from (or enjoy driving car more) having less cruise rpm every minute/all the time your driving your car locally at 55-60mph (not to mention if you hit interstate once in a while) with 3:36's or if you will enjoy driving the car more with higher/more cruise rpm all the time your driving the car with 3:55's just to have bearly noticeable inc in perf a couple times yrly you take the car to the strip.

Good luck either way you choose to go.

Scott
 
#33 ·
After thinking about it and weighing the pros and cons I think the posi with the 3.36s will be the way to go ill have a nice cruise on the interstate with the 28 in tall tires and converter and i bet if you were able to try the 3.36 and the 3.55 one right after the other at the track I bet the difference wouldnt even be a 10th of a sec
 
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