dsavio

i am thinking of putting in new 4:11 gears in my car for my new tremec t 56 trans what rpm is to high that will burn out my new motor is 3000 ok what is the stock crusing rpm for manual transmission car?

thanks
Dave

Pukka

Depends on how you define "stock" cruising speed.

With stock gears, I'd be doing 75mph@2000rpm in 5th gear.
With my current setup I'm at 70mph@2000rpm in 5th gear.

Your gears are steeper so you would see much higher rpms @ speed, however having a 6th gear definitely helps.

Stock 305/350's weren't built for high rpm use. The highest I've ever cruised at on the highway was 3000rpm/90+mph for about 2 hours with no problems.

RB83L69

Every 60s and 70s muscle car came with 3.73 gears and a trans with a 1:1 high gear, whether a 4-speed or a T-350 or T-400... I have had I don't know how many cars set up like that and they worked fine... I had a 79 Z28 with a 4.10, with the POS 180 HP pig 350 that came in it, worked fine....

the T-56 has 2 gears of overdrive, 6th is what, .5 something; so with your 4.10 rear in 6th gear it would be just about like my 305/T-350 El Camino with a 2.73 rear. Don't worry about it.

dsavio

thanks everyone i am going for the 4:11 should perk things up.

87RS402

Like I told you in the other thread, your aftermarket box has a .62 final OD so you can discount what the used T-56 guys are running, they have totally different ratios. If your unsure of what your exact ratio is and you want to check and see if I'm right you can verify your ratios on Tremecs website.

Now if you take that ratio and put it into one of the many online rpm calculators you'll know exactly what your mph will be for a given rpm of vice versa.

What your looking for if you want the best freeway cruise is your rpm to be just starting into the powerband of the cam at your desired cruise speed. If your cam comes on at 1800 rpm I'd say you want to cruise at 2000 rpm. The only real # you left out of your question is what speed do you drive on the freeway at. I ran right at 2000 at 70 mph with my stock set up. Now I run about 2300 or so at the same speed.

I've always advised going with a slightly lower (numericly) gear with a T-56. Since you have 2 OD gears you can still run a faster gear and use 5th instead if your cruising below your desired speed.

Matt86t/a

definately use the 4.11s. My friend has a 76 Camaro LT with 3.90 gears and a three speed auto tranny. A few days ago we took an hour and a half drive down to LBI. He has a worked 355 with heads, cam, carb, intake manifold and other things i can't remember. He was doing i think 75mph (speedo is still set for stock 2.73 gears) at like 4000rpms for at least 40 minutes on the Parkway. His car was fine though and it stayed nice and cold with his full time clutch fan. Trust me, with an extra two gears, you won't have to do anything like that. Unless you were cruising at 125 mph you wouldn't see those rpms with 6 speeds.

~Matt