sPLAIN tO mE 4+3

Corvette C4 transmission, that is. I've been looking at C4's lately, and specifically trying to find one with a manual trans, which is a rare beast at least in these parts. So I find a nice one, and take it for a test drive. First, I didn't really use the electronic overdrive, because I wasn't familiar with it and the salesman didn't seem to know how to use it either. But this car may have had the worst shift feel of any manual trans car I've ever driven. Are they all that bad? If so, I now know why so many have autotragics. The shifter was really hard to get into gears, and the harder I drove it the worse it got. I've owned and driven many old (60's and 70's) muscle cars with pretty tough shifters, but this one really took all the fun out of driving. The sales guy said it was normal, but I'm not sure if he knew what he was talking about or not. Since it's the only one I've driven, I thought I'd ask the GRM brain trust about it.

Super T-10 4spd with a doug nash 2-spd OD unit behind it. The T-10 uses shift rods (think old school 4-spd so they may be out of adjustment if anything has been out of it which would explain the hard shifting. Overall, the shifterr (IMO) was a bit clunky and inexact but not hard to use.

The OD unit will depend on the year. IIRC, 84-86 4+3 are off until engaged, while the 87-88 are on until turned off. The key to longevity with the OD unit is to leave it off and use it as a 5th gear. basically, run through 1-4, then clutch, engage OD switch, let out clutch. It'll survive a lot longer and not jolt you as hard when it tries to engage at it's own time which is usually under load etc. Think: automatic trans shifting without the "cushion" of the Torque converter.

In reply to Bobzilla:

Thanks, but how is the overdrive intended to be used? Is it one overdrive or three? I'm just trying to understand how it was designed to be used, even if that's not the best way to use it.
And it sounds like you are thinking that the shifter in the car I drove may not be working correctly? Probably the best way to describe it is that the car was not fun to drive. I couldn't shift fast enough, so it would lose RPM and acceleration would end up kind of jerky, not smooth. Its the first time I think ever that I wished I had an automatic.

The trans itself is a T10, so yeah it's an old school trans. The shifter may need to be adjusted, crawling under the car is a bit rough as you can imagine. I put a short shift kit on mine and it made a huge improvement as well.

The overdrive is best left off until you need it. Start the car, click the button to 'disarm' the O/D and just drive it like a 4 speed. Press the clutch and hit the button again to engage it when you want it. (pressing the clutch isn't required, but helps reduce the shock to the driveline when shifting.) Just remember to turn it back off again! If left on all the time, the O/D engages and disengages on it's own, lugging the motor and giving the feel of a auto trans 'hunting' for the right gear.

Basiclly you've got a 4-speed manual hooked to a 2 speed automatic. The autotrans has ratio's of 1:1 and .068:1. The theroy of operation is this:

Under hard acceleration the O/D stays in low (1:1) otherwise it engages in 2,3,4 gears. Mat the pedal with the O/D on and it will shift out of .68 in to 1:1 like an auto on kick down.

All this results in the jerky, poor driving you described. So most just leave it off until you hit the freeway.

In reply to Gearheadotaku:

Thanks. At one point I think the OD was engaged and was lugging the engine down when I let off the gas. I got it turned off, but then wondered how it was supposed to operate.
I've had cars with T-10's, and while they didn't exactly shift well compared to today's cars, they shifted better than this one. If its really just like the old school linkage, then I'm thinking the joints are stiff and need lubed. It was just really hard to get into gears. The rest of the car was really nice, except for a broken drivers seat that I'm sure could be fixed. They wanted $5995 for it. It was a one owner car with 113k on it. Do you guys think that it would be a good deal at $5k?

Here's the ad:

http://www.autotrader.com/cars-for-sale/vehicledetails.xhtml?zip=44278&endYear=2015&showcaseOwnerId=76224&startYear=1981&transmissionCode=MAN&transmissionCodes=MAN&searchRadius=25&maxPrice=6000&showcaseListingId=371989410&minPrice=1000&listingId=370625649&Log=0

The OD unit can be used for gears 2-4. So you theoretically could go 1-2, 2-2OD, 2OD-3, 3-3OD, 3OD-4,4-4OD. The problem is the ratios dont work out quite like that. IIRC, 2OD and 3OD were a taller ratio over 3rd and 4th non-OD. So if you theoretically went 2OD to 3rd, you'd go backwards a little in gear ratios.

OD unit is best used when cruising to lower rpm's. In town or 40-45mph speed limits, 3OD worked really well.

EDIT: That link is an 88, so the default setting for the OD is "on". So to turn it off, you start the car, click the button once and drive. Then when you want to engage it, you click the button to turn it on.

Those look the like the 16" wheels that were only used for a year or 2. Very, very rare. Down side is they were only used on the basest of base models. Car looks clean, rare (and very nice) color. 1988 is a good year to have, several brake and suspension upgrades were added that year. That's not the correct radio but who cares. I like the car and price seems reasonable. 5k out the door would be super deal.

^ Yeah, overall the car is clean. That is the base model car, so the suspension and brakes are the smaller/softer variety. If it has a good service history, it would be a decent buy.

In reply to Gearheadotaku:

Yeah, I really like the color. My first car was a '68 Camaro that was Corvette Bronze, and this color is similar, only darker. And the paint is good, no flaws. Tires look almost new. The engine idled and ran a little rough, but may just need some tuning or injectors cleaned. I actually don't like the wheels much. Could I get some money for them? I looked at another C4 that had C5 Z-06 wheels on it, and they looked really good. I'd probably try to do that on this car.

Hmm... how hard would it be to re-wire the o/d so it works like an old Volvo or LBC (default off)?

Otherwise, it sounds like a Laycock o/d used by Volvo and LBC's.

If you decide to sell the wheels, try corvetteforum.com

What would you're plans be for this car?

My plans? Well, I don't know. For a while now I've been trying to figure out the car situation with my boys. When they were in high school they shared the CRX. Now they are in college, Brad away and Steve commutes. Last year Brad didn't need a car, but he will next year. So far this summer one has been driving the CRX and one the Sierra, and you can imagine the complaining from Steve about the truck and it's gas mileage.
I want to sell the truck and replace it with something he would drive. My better judgement says to buy a boring economy car, but to be fair to the boys I either have to buy something equivalent to the CRX, or sell it and buy two equally boring, reliable and economical cars. I'm tired of cars I need to repair frequently, so I'm leaning towards the last option. But the car guy in me says "life's too short to drive boring cars".
These cars are mine. I'm not giving them to my boys, they are just using them, and I don't really want to own boring cars, so there's the dilemma. Both boys have had driver training well beyond the average teenager and have never given me any reason to doubt that they drive responsibly, so I have no problem with them driving an '88 Corvette, but its probably not the wisest choice either, especially considering it will be driven all year long.
Sorry for the ramble, but I've been conflicted about this for some time. Maybe you guys can help me get it straight in my mind?

I hate to be that guy, but have you thought of an auto instead if you're going for an L98 car? I've driven the 4+3 and have lot's of time in my FIL's old auto L98 car. That car / trans combo's is one of the best suited to an auto of anything I've ever driven, it was the car that convinced me auto's weren't the sporn of the devil only to be used if you had a limb missing. I honestly prefer a C4 L98 car with the auto. Seriously, go try one.

In reply to Adrian_Thompson:

I have tried one, and based on the one manual car I've driven, I have to agree with you. But I'm not sure the 4+3 I drove was typical. If it was easier to shift I think I'd prefer it over an auto.

I autocrossed my '86 C4 automatic and stomped the manual cars. The C4 is well suited to the automatic and unless you want to buy the newer 6 speed I would avoid the manual. It also got great gas mileage averaging in the 20's.

The OD is pretty fun when it kicks down, but I try not to do it because, like others have said, its hard on them. One time I was going coming off the interstate, od on, and downshifting to go through and intersection and turn left, so got to 2nd gear, od still on, and am starting through the intersection when the light turns yellow so I get on it a little to move through quickly, well OD kicks down and the car shoots sideways....weeeeee! lol

Generally I get in the car, start it up, then turn od off, then don't use it again until I need a "5th" gear.

oh if you didn't know I bought Bobzilla's old c4.

as far as the trans feel...it's probably less clunky than the 915 in my 911, but I guess that isn't saying a whole lot. To me it feels good enough....doesn't ruin the driving experience or anything, so count me in the group that thinks the one you drove need s little TLC.

Another option is to look for an 89 and up with the 6 speed.

You could get a 3-stick race car shifter for it. IIRC the reverse is on it's own shift rod for that model, so add in a spring and appropriate push on/ push off micro switch on that shift stick in the direction opposite of reverse to engage or dis-engage the OD and you'd be set. I drove a Ramcharger for a year with 2-sticks on the floor instead of the column shift and it only took a couple of trips to get used to it. Bonus for rendering it theft proof.

http://www.speedwaymotors.com/4-Speed-Stock-Car-Racing-Shifter,2670.html

It's what I'm planning on doing with mine, anyway.

In reply to Cotton:

What brand/model is the 6 speed?

bravenrace wrote: In reply to Cotton: What brand/model is the 6 speed?

ZF, don't konw the model number though

so you were right up the street, test driving a c4, and did not bring me along?

thanks, buddy!

Yeah, I call shenanigans!

patgizz wrote: so you were right up the street, test driving a c4, and did not bring me along? thanks, buddy!

I forgot.