[bosco200]

I have a 1972 C20 with a 250 ci inline 6 with a 4 speed manual tranny....i am going to be putting in either a 350 or a 400 and im wanting to put in a different transmission either a 5 or 6 speed because my rear end has 4.56's and I need some more top end cuz im red lining at 60 mph....should I go with a 5 or a 6 speed and how hard to you think this swap will be....im thinking of putting a camaro transmission in.

[bosco200]

Really I know someone knows.

[68NovaSS]

It's up to you, look at the final drive ratio of each trans and determine if that put's you in the rpm range you want for cruising. There are rpm calculators all over the internet, do a search.

Moving to the transmission forum.

[SSedan64]

This sounds familiar vibration that no one can solve

[oldbogie]

Originally Posted by bosco200

I have a 1972 C20 with a 250 ci inline 6 with a 4 speed manual tranny....i am going to be putting in either a 350 or a 400 and im wanting to put in a different transmission either a 5 or 6 speed because my rear end has 4.56's and I need some more top end cuz im red lining at 60 mph....should I go with a 5 or a 6 speed and how hard to you think this swap will be....im thinking of putting a camaro transmission in.

This is more budget related than anything. A 5 speed will give you some overdrive that will be helpful, but in my opinion the Tremac is at, if not above, its torque in versus vehicle mass limit being pinned between a 350 or 400 and a 3/4 ton truck. But this is the slightly less expensive solution.

A T56 give you 2 over-drives a little and a lot which certainly will work against a 4.56 set of gears out on the highway. These are beefier than the 5 speeds which will prove to be a happier marriage when trapped between a big inch small block and a heavy pickup. But these babies tend to be costly even used 'cause everybody wants one.

Another choice that is 700R4 or the later version as the 4L60 not to be confused with the electronically controlled 4L60E. These, while automatics, do feature a lock up converter with an overdrive in 4th. They are a lot more plentiful in the wrecking yards and therefore less expensive, though by the time you add the price of rebuilding one or buying one rebuilt the cost isn't a lot less than buying a T56. That's something you need to look at before going ahead. Also the 4 speed GM automatics have a pretty deep low which you certainly don't need with your rear gear ratio unless you use the truck with a 7 bottom plow.

Bogie

[OneMoreTime]

That kind of situation is almost made to order for a gear vendors overdrive unit..that way you maintain the existing gearing for towing and pulling and have the OD feature for crusing..just my take tho..

Sam

[bosco200]

How much does a used one go for.