Non-locking vs locking 700r4
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
Non-locking vs locking 700r4
Roughly how much of a difference in RPM would you see on the highway between a non-locking 700r4 and a locking?
I know the non-locking will create more heat, but will it be a really noticable difference in RPM? If so Im going to be a little pissed because the whole reason I spent the money to swap to OD was so highway driving would be better, but my transmission builder recommended a non-lockup.
FYI I have a 3.70 rearend.
I know the non-locking will create more heat, but will it be a really noticable difference in RPM? If so Im going to be a little pissed because the whole reason I spent the money to swap to OD was so highway driving would be better, but my transmission builder recommended a non-lockup.
FYI I have a 3.70 rearend.
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
I did one of those RPM calculators just for the heck of it. I calculated my tire height, and with BFG Radial TAs 255/60R15, my tire height is about 12"....using the formula Tire Height = Wheel size + 2(Section Height).
With that, plus the 3.70 rear and a OD gear ratio of 0.70 it came up with 2091 @ 65mph and 2547 @ 80mph, that seems pretty good........of course I dont know if that takes into account lock up or not.
Do those numbers seem accurate?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
You should be able to see when the lockup clutch is activated by noting a reduction in the RPM's on your tach. Slowly accelerate from a stop and note the point at which each [range] shift is made. The fourth range should come in at about 40-45 mph. When you first feel that shift being made, note the rpms and watch the tach. Very shortly after the shift to fourth range, you should see another rpm drop of a few hundred rpm; that is the lockup clutch coming on. If you do NOT see that drop as you continue to increase speed, level off your speed [50 mph, or so] and see if it comes on then. If not, your lockup clutch is not activating. I believe {and I could be wrong} that all 700-R4 trannies had lockup clutches in them.
Instructor
Joined: Mar 2010
Posts: 121
Likes: 0
From: Dallas Texas
The RPM calculator will not account for slip, so those numbers would only be valid for a standard transmission or an automatic with a lockup converter. The slip in a converter depends on it's stall speed. The only time I would choose a non-lockup converter would be on a drag-race only car. For a street driven car, the non-lockup option only increses heat and fuel consumption. Having a lockup is like having an extra gear, and it saves wear on the transmission. Hope this helps -Jeff
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
You should be able to see when the lockup clutch is activated by noting a reduction in the RPM's on your tach. Slowly accelerate from a stop and note the point at which each [range] shift is made. The fourth range should come in at about 40-45 mph. When you first feel that shift being made, note the rpms and watch the tach. Very shortly after the shift to fourth range, you should see another rpm drop of a few hundred rpm; that is the lockup clutch coming on. If you do NOT see that drop as you continue to increase speed, level off your speed [50 mph, or so] and see if it comes on then. If not, your lockup clutch is not activating. I believe {and I could be wrong} that all 700-R4 trannies had lockup clutches in them.
He modified the valve body so it is now fully non-lockup transmission.
Instructor
Joined: Mar 2010
Posts: 121
Likes: 0
From: Dallas Texas
You should be able to see when the lockup clutch is activated by noting a reduction in the RPM's on your tach. Slowly accelerate from a stop and note the point at which each [range] shift is made. The fourth range should come in at about 40-45 mph. When you first feel that shift being made, note the rpms and watch the tach. Very shortly after the shift to fourth range, you should see another rpm drop of a few hundred rpm; that is the lockup clutch coming on. If you do NOT see that drop as you continue to increase speed, level off your speed [50 mph, or so] and see if it comes on then. If not, your lockup clutch is not activating. I believe {and I could be wrong} that all 700-R4 trannies had lockup clutches in them.
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Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
The RPM calculator will not account for slip, so those numbers would only be valid for a standard transmission or an automatic with a lockup converter. The slip in a converter depends on it's stall speed. The only time I would choose a non-lockup converter would be on a drag-race only car. For a street driven car, the non-lockup option only increses heat and fuel consumption. Having a lockup is like having an extra gear, and it saves wear on the transmission. Hope this helps -Jeff
Instructor
Joined: Mar 2010
Posts: 121
Likes: 0
From: Dallas Texas
I think you'll be fine with highway driving, the transmission you'll be running is tough and the overdrive will be much better for you than the three speed. Enjoy the car, that's what it's all about. 
-Jeff
-Jeff
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
The support and information on these sites has been great! Thanks for that
Instructor
Joined: Oct 2009
Posts: 107
Likes: 0
From: Cabot AR
I have to agree with the others, for a street driven car the lock up is the way to go. To answer your question, in my 81 the lock up reduces my hwy cruise rpm by about 600 rpm, well worth having with fuel prices going up all the time. Your tranny builder probably just put in a dummy converter, thats what most do to eliminate the lock up. If you decide to get the lock up to work its mainly just replacing the converter and a couple pieces inside the pan, no big deal. Did the builder install a shift kit for the trans?
Bill
Bill
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
I have to agree with the others, for a street driven car the lock up is the way to go. To answer your question, in my 81 the lock up reduces my hwy cruise rpm by about 600 rpm, well worth having with fuel prices going up all the time. Your tranny builder probably just put in a dummy converter, thats what most do to eliminate the lock up. If you decide to get the lock up to work its mainly just replacing the converter and a couple pieces inside the pan, no big deal. Did the builder install a shift kit for the trans?
Bill
Bill
Yeah he installed a B&M shift kit. The whole trans was rebuilt and strengthened to hold all the power from the new 383. Corvette servo, high energy bands, stronger boost valves....
Im assuming it'd be a pain to switch back to lock up....
P.S. Thanks for your PM response, Ill let you know how it goes today with the continuing install. If I still have issues Ill try to take some pictures
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
If you wanted a 'drag' tranny, he set it up correctly. The lockup function has no purpose for a drag car. But, if you are going to drive it on the highway, you definitely want to have the lockup feature.
Decide which way you want to go. If you want lockup for 'normal' driving, call the tranny builder and ask him what it would take to add that function. It might be as simple as a converter swap which would be a few bucks difference for the converter and a labor charge for a [simple] swap. It it required revising the valve body, it would be more costly. But, remind him that it was HE who recommended that it NOT have lockup. Frankly, I can think of no reason why not to have it.
Decide which way you want to go. If you want lockup for 'normal' driving, call the tranny builder and ask him what it would take to add that function. It might be as simple as a converter swap which would be a few bucks difference for the converter and a labor charge for a [simple] swap. It it required revising the valve body, it would be more costly. But, remind him that it was HE who recommended that it NOT have lockup. Frankly, I can think of no reason why not to have it.
Thread Starter
Racer
Joined: Oct 2009
Posts: 305
Likes: 45
If you wanted a 'drag' tranny, he set it up correctly. The lockup function has no purpose for a drag car. But, if you are going to drive it on the highway, you definitely want to have the lockup feature.
Decide which way you want to go. If you want lockup for 'normal' driving, call the tranny builder and ask him what it would take to add that function. It might be as simple as a converter swap which would be a few bucks difference for the converter and a labor charge for a [simple] swap. It it required revising the valve body, it would be more costly. But, remind him that it was HE who recommended that it NOT have lockup. Frankly, I can think of no reason why not to have it.
Decide which way you want to go. If you want lockup for 'normal' driving, call the tranny builder and ask him what it would take to add that function. It might be as simple as a converter swap which would be a few bucks difference for the converter and a labor charge for a [simple] swap. It it required revising the valve body, it would be more costly. But, remind him that it was HE who recommended that it NOT have lockup. Frankly, I can think of no reason why not to have it.
