Guys considering a TKO, I took a picture to show what 5th gear looks like

[My427stang]

Nothing amazing here, and I couldn't easily do a movie on the highway but a good idea of what cruise RPM looks like at 63 mph. 

TKO-600 with a .64 5th.  4.10 gears (not 4.11 like the sig says), BFG 275/60-15s, 27.50 diameter on an 8 inch rim, inflated to 26 lbs.  Speedo is accurate to less than 1 mph error via cell phone GPS at 75 mph



I slowed down as I took the picture, but at 70, I was at about 2350 RPM.  It really is nice for driving on the highway or a 55 mph rural road, something with taller tires may want less OD ratio, but I really like this combo on the street and can't imagine than many of us are running taller than 275/60-15s at least other than Jay on his drag week car and the truck guys!

Please forgive me for the crooked oil pressure gauge, just put a new brake light swiitch and master cylinder in and clearly bumped it, I have since aligned it to the tach instead of out the drivers side window 

[Drew Pojedinec]

I've got the same tires with 4.30 rear gears and GV overdrive.
Run about 500rpm more than you, so worth it tho.
I'm sure your fuel injection helps too, I think my car wouldn't be as happy at 2000rpms.

[My427stang]

I don't know your build Drew, but this one is 2.63 final now, however it was a 3.70 gear for a while which made it 2.36 final, and back then it had a 1000 Holley and a ported RPM intake with a 1 inch open spacer. Really didn't matter much back then, even with the carb and tall gear it still was happy chugging along.  However, by 489 standards I have a small-ish cam, 242/248 @ .050, .600 lift, although I run it very tight lash too, so it acts a bit bigger.

That 4.30 / GV combo sounds fun too, best of both worlds

[Joe-JDC]

My 2014 pickup has 430 gear and 6 speed auto which cruises at 72 @ 2000 rpm and gets ~18.5 mpg.  I know apples to oranges, but even towing a mustang on trailer it averages 14.0 mpg.  The deep gears don't seem to bother the fuel economy with the double overdrives.  Joe-JDC

[Drew Pojedinec]

I don't know your build Drew, but this one is 2.63 final now, however it was a 3.70 gear for a while which made it 2.36

However, by 489 standards I have a small-ish cam, 242/248 @ .050, .600 lift, although I run it very tight lash too, so it acts a bit bigger.

That 4.30 / GV combo sounds fun too, best of both worlds

My final is 3.31 or therebouts.  I have a slightly larger cam with 43 less ci.  I love the combo of c6/gv.
I just wanted to comment as many builds aren't as happy loafing.
Mine gets grumpy if you don't have the rpms up a little.


I will say my Lykins/Pojedinec 446 has opened the eyes to a few of my Chevy/Dodge Fanatic friends
I think the quote was "How do you have so much torque from 2500-6000 rpms???"  My response was "Dumptruck engine."

[My427stang]

Well I always appreciate your comments and love your build, my point however is, with a bit of tuning people don't have to be afraid of a tall final during cruise, so you are sorta pointing out the exact opposite of what I was trying to show.  Certainly not saying you are wrong, but people sometimes get so hung up on a number or concept, they forget there is more to it.  I know you are talking from experience, so you aren't the target, just pointing out to some that any "hard and fast rule" about tall final gears, shouldn't be hard and fast.

My engine isn't magic, nor is it mild.  To be honest though, I just haven't seen a street engine I couldn't get to run at 2000 at low load.  1200-1500 in 5th like a new car, sure it gets much tougher, but 2000 isn't idling.  The 67 F100 Pickup I did last summer was a 390 with a Thumpr and it was real flat down low due to prior parts selection, but still happy in 5th with a 3.50 and a .68 (2.38).  That was a 396 with a 279 Thumpr, RPM intake and a 800 Edelbrock carb

That being said, I really appreciate that you are talking about your combo, and your car. In fact I especially appreciate it compared to guys who just speak from what they read. I had a Ford guy meet me at a car cruise a few times and hinted that the .64 TKO was no good.  Friendly, but insisted my combo, which he had never even heard run, was clumsy and how baffled he was that I liked it and it "needed" an RR tranny.  So, finally after a few weekends like this, I took him for a ride.

First, went a few miles down the street short shifting, got into 5th by about 40 mph and then accelerated a few times while we talked and he said it was nice, adding a very casual complement that he was surprised how easy it was to get into 5th, then hinted the car must be milder than it sounded....so we turned around and I dropped the hammer a clicked off 1, 2, 3 at 6500.  Passenger's attitude changed significantly....

That being said, you are 100% right, the wilder you go, the less it will be happy chugging around, it's all about the combo, THEN, it's all about tuning the combo.  I looked around to find your build, because I'd be interested to see why it was grumpy, but I couldn't find the details.  Sometimes a little carb and ignition curve tuning goes a long way even with a stout cam, other times playing with cam centerline can help too and not really create any negatives up top.   However, it could just be a happily rowdy 445 FE too, which is way cool too

BTW, here is a little video of it at fast idle.  Normally it idles at about 1000, this was right after start up, 50 degrees outside, 1400 rpm or so. 

https://youtu.be/AtTEvZ2uQmA




 

[jayb]

My Drag Week SOHC is definitely not all that happy under 3000 RPM; almost sounds like its missing.  But so what, it cruises at 65 at 2500 RPM and is happy to do it, even though it sounds like its limping a little.  No problems getting down the road at 2000-2500 RPM.  Overdrives or overdrive gears are wunnerful...

[cjshaker]

Even fuel injection and/or careful carb tuning won't cure an unhappy engine at low RPM's when you have reversion going on in the intake from a healthy cam. My engine doesn't particularly like anything under 2500 RPM when it's in 4th gear, especially with the short stroke, but like Jay's, it'll chug along ok. Having a longer stroke, like yours and Jay's engine would smooth out that low RPM driving when it's under moderate load. The change to 4.30 gears made that easier for me, but I'd really like to have a Gear Vendors now, for highway/interstate driving. If I did, I'd probably bump my gearing to 4.56.

I can't even count how many times I got passed during Drag Week, by cars with GV overdrives, cruising along at 65+ MPH, sounding like they were barely on fast idle.  I missed winning a GV overdrive unit at the awards ceremony at DW by ONE stinking number 

[My427stang]

I am glad you guys posted, this is a good discussion.  I originally wrote a long post and went to do some math and closed the window....WTFO   LOL

So, an 8 sec street car with a trailer can handle 2000-2500, appreciate your feedback Jay.  I'll let the engineers post exacts, but my guess is maintaining 65 doesn't take much more than 50 hp, even if it is 100, all you are trading is efficiency at worst

Doug, I agree, there are no absolutes, some cars will be less happy, but you can manage reversion, you can't eliminate it, and at worse levels it becomes extremely inefficient, but if you treat it like a lean mixture in terms of timing, you can get a long way.  Flattening the advance curve with more initial, careful IAB/IFR selection, intake port to head sizing, a real good exhaust, and advancing the cam a bit all help.  I do agree though, at some point, you have to trade WOT performance and that will be different for everyone

With EFI though, all that and more.  Injector slope and pulse width changes, injector spray pattern changes, injector timing based on a closed valve to heat the fuel, injector slope/PW, and timing based on my cam timing, ignition timing based on load, pressure, engine or ambient temp, as well as airflow, all of these things can offset that lean or diluted mixture.  Granted the hand held TBI systems won't do much more than a carb, but there are areas you can make gains

All of that though, Brent and I had a discussion yesterday about overlap, I'd be interested to see where you are, and I'd love to start wrapping your discussion about stroke into it as well.   My car is 71 degrees overlap with 4.25 (but maybe more than it seems as I have valve lash at .012 instead of .026 per the card), the F-100 I recently did was a hyd at 74 degrees overlap with a 3.78 stroke, my truck is a baby at 58 degrees overlap with a 4.25 stroke, all are med riser ports of varying degrees .  FYI I brought the truck up because it is a carbed 3.50 geared 4100 lb 4x4 with 33 inch tall tires, it'd be equiv to a 2.76 final with 26 inch tires in a Galaxie-ish.

Additionally, like you commented on gear choice, I did get better fuel mileage and acceleration everywhere when I went from a 3.70 to a 4.10, so there are diminishing returns

The last comment I will make though is I do expect the AT guys may generate more heat with a big converter, but even then, a converter stalls at a certain resistance, loafing along, it just isn't loaded that hard

Let me close this that I am in NO way saying all combos will smoothly accelerate like a 70s Caddy in OD, but I am saying that they run better than people think when you are loafing around and worst case, drop a gear.

[Drew Pojedinec]

All great information.  Thanks for the few tips as well Ross!

That said, I think the reason I wanted to post initially, is that I think a lot of people just build an engine and expect it to work outside of it's limits.

I've always been more of a "rear end/transmission" tuner simply because I never had the money to make huge changes to the engine.  I'm not very educated or experienced on a manual transmission with a performance vehicle, but I can say that one of THE most important things with an auto is very careful and honest convertor selection.  PTC/Broader/et el are fantastic at this, BUT the purchaser needs to let them know the real usage of the car.
I love the fact that my convertor is so loose until part throttle at speed when it slowly tightens up.... makes for a great combo.

As such, I always think that the rear gears/convertor/overdrive is all part of the package when designing an engine.
If I wanted a TKO with .64 overdrive, I would be building the engine to allow that.  Rear gears are not just a static thing to work around, they are for tuning.... it may seem small, but going to 4.30 gears instead of 4.10's very well may result in an engine that is happy everywhere.

That said, I think for my own vehicle I have most everything sorted out, some minor tweaks to carb/timing are forthcoming and I think will make some improvements.  Running vacuum advance will most likely help some in the efficiency department as well.

Great discussion, thanks for bringing it up,
Dp

[blykins]

I have the most troubles with "bucking" on hydraulic roller FE's in cars with high rearend ratios.  I'm one of the .82 OD supporters for that reason, although in Ross' case, with a milder camshaft and a 4.10 gear, I would have probably went the .64 OD direction as well. 

As a comparison, a hydraulic roller grind in an FE that doesn't sound like a solid cam will be on the lazy side in terms of lobe aggression.  On a lot of my 482's when I want a 5500-6000 rpm horsepower peak, I'll generally use some of the Thumpr or HUC lobes from Comp.  A 243/249 @ .050" hydraulic roller with a 110/104 arrangement will have 85 degrees of overlap.  A little larger camshaft would be a 247/255 @ .050".  It would have 86 degrees of overlap. 

Hydraulic rollers in FE's can be a balance....a more aggressive lobe with higher DCR and less overlap will sound like a sewing machine.  A quiet camshaft will have lower DCR and higher overlap.

With all that rambling being done, a lot of overlap with a typical 3.31-3.50 gear ratio that I see in a lot of Cobras and cruisers, just don't seem to agree with each other when using a .64 OD. 

A TKO 600 with a .64, 3.31 gear, with a 26" tire would put the speedo at 73 mph @ 2000 rpm.  I think that would be walking the thin line there and 55-60 would definitely be a no-no.  Dropping down to 4th gear would put you at 2600 rpm at 60, which is not lugging, but not singing either, so that's do-able. 

A TKO 600 with a .82, 3.31 gear, with a 26" tire would put the speedometer at 70 mph @ 2400 rpm, which is a pretty sweet spot.  At 60 mph, you're at 2200.  In my mind, you're going to be pretty safe at both rpms there without much fuss and without having to run in 4th gear at 60 mph.   

Obviously, I'm not going to be an overdrive nazi about either scenario, but as pointed out above, the whole engine/car/transmission/rearend combo needs to be looked at, as well as where the most driving will occur.....55-60 or 65-70.

[jayb]

For a guy like me, the car is either ON or OFF, RACE or STREET.  On the street, as long as the car gets me from point A to point B and allows me the usual requirements (decent passing performance, easy low speed cruising on the highway, good cooling, etc.), I'm happy.  I don't get into any stoplight to stoplight drags, and accelerating away hard from any low speed situation doesn't matter at all to me.

On the race track, well, it had better be FAST!

Over the years at Drag Week I've steadily gone up in converter stall speed, with no ill effects on street performance.  Both my Galaxie and my Shelby clone have converters that stall in the 6000-6400 RPM range.  Both cars sail down the freeway at 2500-3000 RPM with no problems.  All I use is good fluid (ATI Super F) and a plate type transmission cooler in front of the radiator, about 6" X 9" in size.  When I had a trans temp gauge on the Galaxie it ran 10 degrees over the water temperature under all conditions.  I guess what I'm saying is that high stall converters don't have to heat up the trans fluid.

Also, with a direct injected EFI system I think you have such flexible tuning capabilities that you can minimize any issues with running a big cam on the street.  The cams in my Shelby clone are 292@0.050, and the engine idles easily at 1000 RPM, doesn't die at stop lights or stop signs, has decent off-idle  response, etc. 

To me its amazing what you can do with all the technology available these days...

[My427stang]

A TKO 600 with a .64, 3.31 gear, with a 26" tire would put the speedo at 73 mph @ 2000 rpm.  I think that would be walking the thin line there and 55-60 would definitely be a no-no.  Dropping down to 4th gear would put you at 2600 rpm at 60, which is not lugging, but not singing either, so that's do-able. 

A TKO 600 with a .82, 3.31 gear, with a 26" tire would put the speedometer at 70 mph @ 2400 rpm, which is a pretty sweet spot.  At 60 mph, you're at 2200.  In my mind, you're going to be pretty safe at both rpms there without much fuss and without having to run in 4th gear at 60 mph.   

You bring up a very good point.  My technique has been gear for 1st and OD.  So in the Cobra, it's likely light enough and has enough of a traction issue that 9.49:1 SLR is enough, and if that's good for the car, then a 2.11 compound OD gear from a .64 would be silly.  I'd also go with a .82 in that case.  Ironically, the .82 works out to be a 2.71 compound ratio which is right around where I call good.

However, in a truck, heavy car, etc that 9.49:1 would likely not be the right SLR.  Even with my Mustang, despite it somehow getting a reputation as a truck motor lately      the 3.70 * 2.87 = 10.61 was not as good around town or through the gears, so although the .82 might have given me enough overdrive with a 3.70 gear, I feel I would have left power and drivability on the table if I would have went with an .82 OD and not deeper gears. 

That little F100 was an oddball too that required looking at both ends, it has a 3.27 1st, which causes it's own issues.  3.50*3.27=11.44 SLR, so let's say I stopped at my own limit on the street at about 12.5 SLR, 12.5/3.27 would have been a rear gear choice of 3.82.  Which until the Harley bug bit the owner, we were planning a 3.89 or 3.91.  In that case, a 3.91 would have been a final drive of 2.66 with the small TKO's .68.    As it was good with the 3.50s, it'd only have been better with the 3.89 and right in the same range that we are talking with mine or the Cobra example

I guess if I had to do a loose rule of thumb, I'd say pick a gear and tranny combo that allows for first gear based on the weight of the car, then limit the final to 2.65-3.00. There will be a couple of ways to skin the cat, but as your SLR gets deeper, the taller OD will get more attractive

Regardless, I still think that carb and ignition tuning for the street is quickly becoming a lost art, but that's OK because a good EFI system makes it way faster to do and allows less compromise

[Autoholic]

For those that have a GV under/over unit, how well do you like it? Reading up on it, sounds like an interesting invention that has been around for a long time. For someone interested in keeping a car original but wants an overdrive, this sounds like the right product to use a toploader.

[Drew Pojedinec]

I love my GV.  Thinking of buying another for when I redo my truck.
A heavy car like mine needs some gear.

I use it behind a c6, which isn't an original transmission for this car, but is a simple to build transmission on the cheap.  I didn't want a manual trans in my car..... I'm a little backwards here, I like a performance car with an auto and like a work truck with a manual.
Using any other automatic would have been annoying and expensive.  I did the math on building an AOD that would survive behind my engine and it didn't seem a good plan.

In reality for me with a car, it's just a fourth gear.  I suspect if I had motorhome of something like that, 2nd over would be handy for taking a long grade.  The notion that a GV makes a 3 speed a 6 speed isn't really true.  I guess it technically is, but I think it would be incredibly annoying to use it as such.  In a heavy towing application I can't see using 1st over as the driveshaft needs to be a certain speed in order to create the hydraulic pressure required to hold the clutch.
It's a shame that US Gear stopped making their Dual Range unit, as it was really more appropriate for heavy vehicles as it was more like a manual transmission two speed rear, and could do REAL gear splitting (It was the old Doug Nash Unit).

Gear Vendor is super simple to rebuild as well..... a kit with the clutch is around $200.

I got my Gear Vendor from behind a 1990 Fleetwood motorhome with a 460 and c6, it was dirt cheap..... The next one I'll probably have to buy new, but it's worth keeping an eye on junkyards.

Good luck
Drew