shmoky

I tried a search but no luck.

Anyone added/heard of an overdrive that spilts the gears? Found a company that makes a unit that is added to the rear of the tranny and acts like a splitter. I am aware that the first couple of gears won't be needed to be split but 4th gear would be nice. It would give my 4th 'over' a ration of 0.78 and should be okay for hi-way cruising.

I have a '68 with M21 4 speed.

shmoky

markdtn

Yes, it's called a 4+3 and was available in '84-'88 C4s. I have never heard of anyone swapping one into a C3.

You could also get a Gear Vendors Overdrive unit.

You are probably better with a 6-speed swap.

tfi racing

Someone else may know more,but I don't think the Gear Vendors unit will fit thes cars without some serious tunnel mods.Typically they are used on trucks and motorhomes where space is not so much of an issue.Ask the C4 guys about the 4+3 unit,I don't think many are too impressed with that setup.

brownc00

For what it's worth...the 4+3 is really a decent transmission and the overdrive lasts a LONG time if you disable the computer turning it on and off all the time.

My neighbor runs one in his 73 so I know they fit in C3s. He love it.

WESCH

Hi

The Gear Vendors overdrive is very expensive. Better to install a TKO overdrive. Vettes do not need any 2nd or 3rd gear overdrive.

I don't know about fitting a 4+3 from a C4 into a C3. What's the benefit ?

Or better, what's the benefit to a TKO 5 speed overdrive ?

Rgds. Günther

fugawi

your better off going with a kiesler tko. about the same price, and a drop in fit.

shmoky

That's what I thought but heard about it and thought I would ask here. Knew I would get some responses to guide me.

The TKO is a little more $$ but the benefits are so much more.
shmoky

KeislerSales

Exactly, not to mention your driveshaft would be what, a foot long?

battsup

I had asked about the overdrive unit from the C4 before as well and every1 was quick to jump and say that it was no good. Considering that the 4+3 transmission is the same trans as the late c3's with the 4 speed just with an overdrive attachment. Those that do a 5 speed conversion and source their own parts usually get their drive shaft shortened for $200 or so. I can't see the cost of the overdrive unit being more than 200-400 bux. That still puts you under the $1000 range whereas you're looking at over $3000 to get a keisler, plus for those of us with manual transmissions already we have to go through the hassle of cutting the cross member and then figuring out a way to attach it back together. My uncle had an 86 corvette with the 4+3 for 15 years and he always boasted about it, never had a single problem with it. But maybe he's the exception.

Brownc00 I'd like to hear more about your neighbour's car. Would it be possible for you to ask him some questions as to what was involved in his swap and how much it cost?

Raphiki

With the Keisler kit you get a lot more that just the OD trans. The trans drops into place with no mods, comes with all the parts you need right down to the shorter drive shaft, speedo gear, mounts, nuts and bolts and a great shifter. I installed mine last summer and love it! Best mod I've made.

battsup

Yes the keisler kit is a good bolt in kit that has worked great for many members on here. However to spend $3 grand on a transmission you would be better off spending another 2-3 grand and doing an LSX conversion. Especially for some1 in Canada such as myself, it would cost me $4000 to get a keisler kit after shipping and currency conversion. At that price it doesn't make any sense to do the swap, especially when a full LSX conversion can be done around and even under $6000 with a T-56!

63mako

Schmoky just built a new High HP motor for his car. The TKO is a much better option. Then he has a new engine/new trans. An LSX/T56 conversion is a long way from a bolt in installation and $6000 would be a very conservative estimate and end up with used components thoughout. So would an overdrive for under $1000. Don't know how you would do that where it could hold up to his power level. TKO is the answer. Maybe talk to Kevin @ Vettesbydesign. Forum sponser, great guy and hungry. Probably figure out how get it to you cheaper.

shmoky

Thanx Kevin (63mako). Yes I have talked to Kevin (vbd) about the TKO and he had the BEST price. Will be dealing with him when the time is right (Canadian $$$ gets stronger )

I figured that the TKO was the right way to go but heard about this OD unit and thought I would ask. And you're right about the new high HP motor. I DON'T need to get another motor.



shmoky

KeislerSales

Do your homework and call us, we will beat ANY competitors price on a comparable kit.

Drunken Peacock

I looked into the overdrive unit (Gear Vendors) and it's close to $3K.

brownc00

Sure, I'll ask him the next time I see him. Like you said, it is the same 4 spd T10 that GM used for several years with a Doug Nash overdrive on the back. I doubt it would require much more than a shorter rear shaft in a 4spd car to do the conversion. They are quite decent if you dump the computer controlled part of them and just turn on overdrive when you want it on.

roscobbc

Didn't Hone manufacture an 'add-on' overdrive unit back in mid-late 60's - and wasn't it offered as an option on Baldwin Motion cars - also on campers - may be a potential junkyard find? I seem to think these have got good money on Ebay in the past!

myc3

I put a used Gear Vendors (ebay $1200) in my 77 with no more than a small tunnel mod and a shortened drive shaft. Since the 77 has a metal tunnel I only had to use a porta power to open the tunnel a little where it narrows just past the tail shaft. It was done in one afternoon. This was with a 3.70 differential. Lots of fun. Don't be afraid of a GV unit if you have a steel tunnel.

I am now in the process of replacing the engine with a 406 and I will be replacing the Gear Vendors with a D&D Performance Chevy/Viper 6 speed.

JaimeVrod

FOr what it is worth, I have a Gear Vendors unit on my 69 Vette with M21 transmission. I love it. It was on the car when I bought it. It uses a T handle hurst shifter with a button in the handle to electronically activate the overdrive.

carbster09

Always figured the gear vendors set up was sweet still I will go with a 5 speed from someone. Awaiting more feedback about the Kiesler RS series.....sounds like the perfect option?