mikejpss

Why wouldnt that work ?
4th gear in that trans is a 1.00 gear ratio. Providing a 0.90-.92 would provide a 4th gear favorable to cruising speeds,without a trans changeout to a much more expensive setup -5 or 6 speed trans...
Has anyone ever attempted such a feat ?
Can it be done ?
I'd need 3 of em as soon as someone made them !

69427

????

Why not just change to a rear gear that is 10% higher instead? Sounds like less headache and expense than a custom trans gear set.

gkull

I don't know everything, but I do rebuild Texracing T10's. We change the 1-3rd gear ratios to match the tracks and car.

You have to look at the design of the gear clusters and main shaft. They are made as a 1-1 4th gear. No overdrive or under drive. Kind of like the richmond 6 speed 5th gear was always 1-1 Some enterprizing individuals made 4th gear and of course 6th as OD's and then just shifted them 1-2-3-5-4-6

scottyp99

I am certainly not even close to being an expert on transmissions, and I could be totally wrong here, but isn't the 1:1 gear on most any manual transmission a direct drive? I don't think there is a gear to be changed, is there? It's an interesting question, that's for sure.

Scott

mikejpss

Scott,like you I am far from an expert. I posed the question for one reason.:
If the aftermarket trans (read-5 and 6 speed trans) are so much sought after for their cruising ability to reduce gas consumption ( as well as performance in being able to shift thru the gears) ,then why hasnt anyone just made a 'cruise' gear for the current T10 market ? (like myself that is too cheap and too lazy to install a $ 4000. aftermarket system) .
Somewhere, someone knows how to take the T10 4th gear and make it into a 0.90-0.92 gear ratio INSTEAD of the 1.00 ratio it currently has.
It would be a cheap alternative to the aftermarket $ 4000. option, and I for one would buy it, install it and tell others.

76stingracer

4th gear does not go through any gearing in a T10. It is a straight through design. I have heard of options for changing 3rd to a overdrive gear, but with this you loose third. Another option is to add a over drive unit from a early C4. This will give you a overdrive in 2nd, 3rd and 4th. Or change the rear gear to the ration you desire and save some time and money.

aussiejohn

G'day,

Like I said, not feasible. I didn't say "not possible", but it would likely cost more than $4,000. The reason that ALL three and four speed manual transmissions have a 1.00:1 top gear is that the gearsets are designed to have intermeshing gears with different numbers of teeth in the lower ratios to provide more output shaft torque to allow acceleration from rest or easier hill climbing, etc.

Fourth gear is actually a misnomer, there is no "fourth gear" in a four speed gearbox. As scotty said, fourth is just a direct drive with no meshed gears providing a ratio change. Therefore you cannot practically change its ratio.

However, as 76stingracer said, you can change third gear from say 1.5:1 to 0.7:1 and change 1-2-4-3 so that "third" is your overdrive gear. By flipping your 3-4 shift lever arm on the gearbox, your shift pattern remains the same. The downside is that you have a big jump from second gear to the 1.00:1 "third" gear.

Like you, I have often wished that there was a simple way of adding an overdrive to a basically stock four speed gear box. The only way I can think it could be made to work is to throw out the guts of the stock gearbox and put in a completely new gearset with FIVE forward ratios, fourth being 1.00:1 and fifth being an overdrive.

This would require that all the actual gears would have to be "narrower" that the stock ones and even with better quality steel that's available today, the gearbox would likely have less torque capability than the wider stock gears.

Then there's the cost......

Regards from Down Under.

aussiejohn

7t9l82

i know i heard someone made an 833 chrysler 4 speed with 4th gear as an overdrive 3rd gear was 1-1 . seems to me someone else did the muncie.

hugie82

the 833 is being done and PAW might have an adapter to bolt a mopar on a Chevy.

7t9l82

the 833 is a great transmission i used one behind a 454 years ago and found that both Bill Jenkins and Wally Booth did the same in their early Pro- Stock cars