Michail

The T5 in my -86 IROC is starting to sound bad so I am looking for a replacement.

I don't like to change gear much, so I wonder if there is anything besides 4/5-speed manuals with 1:1 highest and the 5/6-speed manuals with overdrive?

What I wish for is a four-speed where the third would be 1:1 and the fourth really high, like 0.5:1 (1:2?) or so. Is there such a beast out there at all?

Autos are for gliders and not an option.

Thanks

84z28350

I have never heard of OD on anything other than 5/6 speeds.

Whats so bad about having to shift one more gear to go into OD?

Ricktpi

If it bothers you that much, get an auto trans.

Johnny Blaze

iTrader: (15)

Yeah, Gm has some 3 speed overdrives in the 50's and 60's.

AlkyIROC

They're all 4 speed trannys. A T5 is a 4 speed with one OD. A T56 is a 4 speed with 2 OD gears. To call it a real 5 or 6 speed tranny, the top gear needs to be 1:1

As for what you're asking, no. GM produced 3 and 4 speed manual trannys but top gear in both is 1:1. The gear spread would be too far apart for what you're asking. A close ratio 4 speed was always prefered because the gear ratios were closer together. This keeps the engine in it's powerband better

Randy82WS7

Stephen's correct

you would have to have a trans customized to have such ratios

IE different gears put into it

good luck

Johnny Blaze

iTrader: (15)

What about the 3speed overdrives that were installed in passenger cars of the 1950s and 1960s? Sure they are useless for his application, but they were 3speed od's.

Michail

Oh well. I was just wondering.

Thanks for the replies!

sofakingdom

iTrader: (1)

I know of no 50s and 60s 3-speeds with overdrive. All my old 50s and early 60s Chevy vehicles had the regular old Chevy 3-speed, anyway.

Put in a T-5 with the low-perf 5th gear, which is .63, and just don't use 1st.

Johnny Blaze

iTrader: (15)

I know 55,6,and 7 belairs had an optional 3 speed overdrive.

Michail

> Put in a T-5 with the low-perf 5th gear, which is .63, and
> just don't use 1st.

Oh, there is such a thing? Cool!

I used to have a Honda CBR929RR that had about 3-4 gears too many. The "powerband" went from about 4-12krpm. I find myself going from first directly to fifth on my IROC all the time, using fourth in traffic. I'd manage fine with three gears, especially when I get the Whipple mounted, but I don't much fancy a 1:1 highest ratio.

sofakingdom

iTrader: (1)

55, 56, & 57 Belairs had an option for a HydraMatic transmission that had 4 speeds (4th was OD). I know, because I had one of those, in a 59 Pontiac. I also might still have the service manual around somewhere for a 57 truck I had (it was a cool truck to have back in the 70s... everybody wanted to buy it.... it was a former Forest Service truck, which was a panel truck with no glass anywere behind the driver), that had similar info.

I had ALOT of the old Chevrolet 3-speed transmissions, which was the only manual that there was back then, before the original Muncie came out in 59. No OD in any of those I can assure you.

Incidentally Mic, if your car is the LG4 (carb) motor, you probably already have that terrible 5th gear. The low-perf cars all through those years got that, for gas mileage. Very anti-performance but gave a couple more feet per gallon.

Michail

Ah yes, now I understand. I got a bit confused for a while there.

I do have an LG4 with a 5-speed where the fifth gear is somewhat high. Not enough to my taste though (my other car is a Buick that does 1500rpm @ 55 mph).

I suppose I can live with a half dozen gears, it just bugs me a tad.

Johnny Blaze

iTrader: (15)

You have to be the first person I have ever heard complain about haveing to many gears!

dyrt

they make 4th gear overdrive gearsets for the rockcrusher.....i saw one in a firebird buiilt for the salt flats. i'm sure if you look into it you can get custom sets for a muncie or t10. you couild always get a lower first gear 4 speed with a 1:1 4th and use 3.23 gears in the rear.

AlkyIROC

My car only has 2 gears. 1.76 first gear (low) and 1:1 second gear (high). I also have a **** load of torque to get me moving off the line that I don't need a real low first gear.

84z28350

Ahh, good 'ol powerglides

I dont think we all have 800hp to get these fat limos moving off the line with one of them though lol

Michail

> You have to be the first person I have ever heard
> complain about haveing to many gears!

It is also kind of a concept thing. A statement that "I don't need no steenkin' gears!"

> they make 4th gear overdrive gearsets for the
> rockcrusher.....i saw one in a firebird buiilt for the salt
> flats. i'm sure if you look into it you can get custom
> sets for a muncie or t10.

That's most interesting! I have been ogling the T10 apprehensively because it is very cheap (and a 4spd), but I did not realize it might be customized.

> you couild always get a lower
> first gear 4 speed with a 1:1 4th and use 3.23 gears in
> the rear.

But this I do not understand. That is not a high gearing if my calculator tells me right. With 245/45-16 tires that would mean 136 mph at 6000 rpm or so, which is kind of ridiculous with a 500+ BHP engine.

The tallest rear gears I have seen would be 2.56:1, which would give 172 mph @ 6krpm. Still much too short for an engine capable of 200+ mph and tire-shredding torque at cruising speed.

> My car only has 2 gears. 1.76 first gear (low) and 1:1
> second gear (high). I also have a **** load of torque to
> get me moving off the line that I don't need a real low
> first gear.

Also, you only sprint up to a speed that is significantly lower than your car is theoretically capable of, I take it?

I would like four gears: one for starts and 0-60 times. One for rolling in slow traffic, one for top speed runs and one for highway cruising.

I suppose I ought to have an auto gearbox, but I don't want one. =/

> I dont think we all have 800hp to get these fat limos
> moving off the line with one of them though lol

Hey! Speak for yourself! ;-]

When I am done with this car, it will be an eco-friendly and rather extreme sportscar running on E85 and compound supercharged using turbo AND a screw compressor. First change (got to wedge things into the budget step by step) will be a naturally aspired Motown 427 smallblock though, and I guess even that will make splinters out of the T5.

My ultimate goal is to be able to show it to on expos like "Look - 600 BHP and no emissions!"

Joe knott

Yes there are 4sp tranny's with overdrive- it was called a doug-
nash unit. actually a T-10. It came out in the 85-86 corvette It
was refered to as the 4+3 unit. "Bullit Proof"

dyrt

well, the g-bodies could be had with a 2.29 gear(http://gnttype.org/numbers/axcodes.html) if you want to gear this thing to make up for the loss of a lower overdrive, but i am not really understanding something....you are doing math to figure out top speed at 6k? what exactly do you plan to do with this car? a t-5 offers a wide range of ratios to get from a stop to a reasonably high cruising speed. if you want to do mach 5 in this car at 1100 rpm it just isn't going to happen. if your car as 3.42 gear then you could use 3.23 or so and get a 4 speed with .84:1(give or take) which would get you closer to the equivalent to a .5:1 overdrive with a 3.42(this, of course, assuming that you have 3.42s) ultimately, what i am getting at is if you want to use a 4-speed and have 4th gear the same as 5th gear with your car as it is, you are going to have to get the best overdrive gear for a 4 speed and change the rear ratio to get your cruising speed where you want it. am i missing your point here?

Michail

This car will be used for wiping the grin off the face of Porsches and BMW M series that are common around here. Not drag racing but spanking highways.

I would like four gears:
1st for starts and 0-60 times.
2nd for rolling in slow traffic.
3rd for top speed runs.
4th for highway cruising.

The third gear would thus match the rpms at peak BHP with the theoretic top speed.

A 427 small block with a somewhat peaky cam should be able to deliver at least 450 BHP @ 6000 rpm with a max torque of about 450-500 lbft. A Camaro with 450 BHP should be able to top 180 mph, meaning that I want 6000 rpms at 180 mph, which with a 1:1 gearbox ratio would demand a rear ring-and-pinion ratio of 2.45:1 or so.

That is probably feasible, but not in third gear in any gearbox I have seen so far. If I then want to do 1500 rpm @ 55 mph or so, then it would require a fourth gear ratio of about 0.5:1, and I have yet to see such a beast.

Things get more complicated at tuning stage 2: blower.

Together with a milder cam, that would mean 550 BHP @ 5500 rpms and 600+ lbft torque. 200 mph @ 5500rpm with a 1:1 third gear would require a 2:1 rear, which does not exist. On the other hand, with this power then the fourth (0.5:1) gear would be top speed gear.

At stage 3 - compound supercharging - which I might not reach this decade - we're talking 800 BHP @ 5000 rpm and 230 mph, but that is mostly a fantasy.

Never mind. I might just drop the idea and get a 5/6-speed and just don't use half of the gears instead. Seems more simple than building a custom 4-speed.

dr1

chrysler made a version of there 4 spd manual with an overdrive 4th gear, i remember cause i wanted to find one
just confirming the existance of such things

on further reading of your posts you sound kinda crazy ;p
the gears do serve a purpose you know.. the rpm drop you would have between your gears would be absolutely ridiculous with the numbers you are giving
you'll be wiping the grin of some faces, but just replacing it with some laughter as they watch you try to get moving

Michail

Heh

Well, if the rpms drop from 6000 to 3000 it is not that much of a problem with a phat 500+ BHP V8 cranking the shaft, is it? It's not a 500cc two-stroker we're talking about...

Actually, I got this idea from my old Honda CBR929RR. With that bike you put it in 6th gear at 30 mph and stayed there for the rest of the day. There was absolutely no reason to gear down whatsoever lest you stop at red lights, because even in 6th you had more power and torque between 30-170 mph than most roads could handle. You just couldn't squeeze the throttle full in any curve, because you would exit the apex with too high speed.

Thus, for the road raging and power levels I'm thinking of, changing gear is rather more than a nuisance than a benefit.

Right now it is all still on paper only, though. I think the moribund 305 in my IROC delivers a whopping 165 BHP or so... Need new engine, transmission, brakes, body stabilizers...

dr1

uhhh i guess it totally depends on what you plan on using the car for.. but currently it doesnt sound like its going to be of much use in any department :P
either way it really doesnt matter because your not going to find the crazy gearsets your coming up with in your head
automatics can get away with lousy gearing because they have a torque convertor getting you more power out
you are either just going to be roasting clutches, or having to get to 5000 rpm just to shift to 2nd

Michail

Look man, I think you are overdoing it trying to make it sound like a bad idea. It would not be at all as extreme as you say. With three gears covering the velocity register we're talking

1st gear: 0-60 @ 6000 rpm
2nd gear: rpms drop to 3000. Pulling to 120 mph @ 6000 rpm
3rd gear: rpms drop to 4500. Pulling to 180 mph @ 6000 rpm
4th gear: rpms drop to ? The car can not maintain top speed at that low power output, so the speed drops. No problem, the fourth would be for cruising anyway.

Basically, this is not much different from starting my current IROC in second gear, skipping third, going to fourth and fifth. And even the current laughable engine can manage that without blowing anything up.

Does a nicely built 427cui pull well from 3000? I would think so. The only abnormal clutch strain I can think of would be that from 0-10 mph or so, because the first gear would be kind of tall and the engine might want to be helped up to rpms where it pulls clean. And is that a problem, really? I'm not going to use a standard clutch for a tuned car.

Never mind, it doesn't seem like a good idea pursuiting such a gearbox anyway, so I suppose I'll be content with a T56 or similar. I already dropped the idea, I'm just defending its validity.

I might need to point out that I am not intending to drag race with this car. I'm going to road race. As in: speeding around the countryside, feeling the traction and accelerating through the curves and blasting past the occasional riceboy on some of the very long, straight and fast roads around here.

Gladstoneiroc

iTrader: (1)

Going with a 26" tire correct? I guess you could with a 2.73 rear 2.5 first 1.5 second 1.0 third .7 fourth. I think you are trying to do much more work than you need to. You are going to have to make a lot of power from 1000 to 6000 not just 3k - 6k.

Motor City Mike

You beat me to it. The "4+3" transmission was a 4-speed manual trans with an automatic overdrive unit on the output shaft end that worked on the top three gears, and was only available on the early C4 Vettes.

Fast355

iTrader: (2)

Leave it to me to bring it up, BUT you COULD get a GM 4spd trasmission with OD in the 80s. IIRC, it is a Saginaw based unit. Ever seen a 4 on TREE? Or 4 on the floor VAN or TRUCK. Look especially in work trucks and vans with the I6 or 305 around 1983-1985 or so.

My 1983 G20 Owners Manual clearly shows the shift pattern with 3 and OD for the standard shift. It also gives mention that the OD is to lower engine rpm and give better fuel mileage. For optimum acceleration shift speeds shift 3-OD @ 75 MPH.

Supermann

another option you could look into is taking a th700 and putting a full manual valve body in it. That way you still have to shift through the gears, but you would have that 3 speed plus OD that you are looking for. Since it seems like you don't like shifting, it would also be helpful cause you don't have to worry about a clutch. You could get one of those for cheap, but I guess you wouldn't be able to get those crazy ratios your looking for. I would just get a set of 2.73s then cause you are going to need something really high to get those speeds you want.

Sonix

iTrader: (1)

ford had a 4 speed (3 + OD) on early '80s mustangs/capris.
Ya know, the ones that were a direct competition to our early 3rd gens??? They got overdrive in an '82 mustang 5.0L, and we didn't... they also later got forged pistons, factory headers, 8.8" rear, etc etc etc....
makes me jealous if they weren't so ugly.

Michail

=] So what I am hearing is that there are - or at least were, 20 years ago - several 3+OD trannies to be found out there? Nice. I think I'll look into it after all.

> another option you could look into is taking a th700 and putting a full
> manual valve body in it.

Sounds intriguing!

I didn't know that was possible. Learn something new every day. =]

Thanks, all!

Sonix

iTrader: (1)

manual valve body still has no clutch though right? you just have to shift it? kinda like a hondamatic from an '82 civic? shudder...
same drawbacks as an auto, but also with the drawbacks of a stick too..... Not my choice, but to each his own...

vbMike

iTrader: (2)

You could get a 3 or 4 speed muncie and then install an electric gear venders overdrive. That way you would only have to shift 3 or 4 gears and then hit a button to get overdrive. However, I believe gear venders overdrive kits go for around $1000.

80smetalfan

Even lower too. My Cutlass rolled out of Detriot with 2.14s, as well as many others with the TH-200C. Got the build sheet to prove it! Needless to say, with the 700, it refuses 4th gear lockup until about 60 (don't know for sure, my speedo is terribly inaccurate), and even then, it's about 1100 rpms. Nice for highway mileage, lol. First at 5000 rpms is 60 mph, 4th at 5000 rpms would be about 270 mph.

I think you need the Doug Nash 4+3, Mic, as previously mentioned. Seems to be what you need. Or a 2.14 g-body axle.