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Street Rod Builder

By October 8, 2009Uncategorized

Most of us spend money building high horsepower motors and back them up with mildly modified automatic transmissions. Builders add higher stall speed converters, deep tranny oil pans and shift linkage. These do little to increase the transmissions ability to deal with all of that power. Before long the stock internal parts are destroyed and you’re buying a new automatic transmission.

Replacing the worn out transmission with another stock piece would be an excercise in futility. Instead, the solution is to build or buy a purpose built automatic transmission to withstand the abuse of high horsepower applications. Gear Star builds every automatic transmission it sells, and it builds them to match a specific vehicle and engine combination. for the ’32 coupe and the 383 small block, Gear Star recommended a Level 3 700R4 which is equipped to handle up to 700 horsepower. It may be slightly overkill for this ’32, but this 700R4 will definitely stand up to the coupe’s power with room to add more horsepower later. A healthy margin of safety is better than replacing a transmission.

Although the ’32 had to suffer the rare indignity of riding in a trailer to Gear Star’s Akron, Ohio facility, the long drive was well worth the effort, considering the results of the swap. Since the 700R4 swap, the ’32 is a brand new car and now drives the way it should have from the beginning. According to those who have ridden in the car since the swap, the owner is completely insane. The car is driven hard and he gives the 700R4 automatic a workout. Gear Star has never once denied a warranty on one of its automatic transmissions. The owner of this ’32 won’t have to pay for another new automatic transmission.

So much about automatic transmissions is a black art to people with little or no automatic transmission experience, here is why the Gear Star 700R4 is so much better. A 700R4 automatic contains in excess of 1,000 individual pieces. Unless you know what you’re doing, you should leave the 700R4 automatic transmission building to companies like Gear Star. It would be quite easy to miss a step in the building process and have to tear the transmission back out and back down to fix what you missed. Even if you don’t have a 700R4, Gear Star can help you with many other GM, Ford and Chrysler automatic transmissions.

Here is a step by step look at rebuilding a Gear Star 700R4:

1) Removing your old transmission is pretty straightforward. Frame designs vary greatly so we’ll focus on the 700R4 automatic transmission rebuild.

2) Upon teardown, one immediate problem Gear Star found was the speedo housing. You can see the numbers 36-39 stamped on the housing, which indicate the range or gear teeth designed to fit inside.

3) Whoever built the transmission bored out the housing to accept a 42-tooth speedo gear, causing bad housing geometry and worn teeth.

4) More problems: The fitting on the right is the correct transmission fitting. The one on the left is what was installed. This is not an error that will kill a tranny, but it is an indicator of sloppy workmanship and a "close enough" mentality.

5) On the right is the old transmission governor, with a new one on the left. The regulator matches shift timing with throttle pressure and valve body settings, and the one that came out of the old transmission was not correct for that application.

6)This 300mm hardened shaft and hardened expanded-capacity drum represent a major upgrade over the factory equipment, with a much gretaer torque capacity compared to the factory equipment. The upgraded materials keep the shaft from breaking the drum.

7) The planetery gear assembly is at the heart of the drum assembly, and of course each rebuilt transmission gets a new planetary set.

8) All new springs help ensure proper shifting

9)One of the new pieces installed in the new drum is this late-model input sprag fitted with a Borg-Warner element.

10) Next come nine heavy-duty Kolene steels and nine Alto Red Eagle frictions.

11) The new steels and fritcions are thinner than the stock steels and frictions, so 50 percent more of them are used compared to a stock transmission.

12) Each pump is machine to ensure a leak-free parallel surface when paired with the opposite half.

13) All bushings inside the pump are upgraded bronze units that exceed OE quality and specifications.

14) The assembled pump slips over the hardened input shaft at the front of the transmission.

15) This level 3 Corvette servo assembly applies additional pressure on th 2-4 servo by increasing oil volume. With Sonnax Super Hold fourth-gear servo, you’ll get 45 percent more oil pressure in fourth gear for increased hold compared to the stock equipment.

16) This assembly is a modified 1-2 accumulator piston and its housing, which improve and regulate the 1-2 shift. Gear Star tailors the combination of springs for different combinations.

17) The springs and pistons inside the valve body make huge difference in the way the transmission feels, and after they’re installed Gear Star can bolt the valve body back to the transmission.

18-19) Each transmission receives a unique combination of valve body shift springs and sleeves designed for a specific application. Gear Star uses particular spring combinations for each transmission application.

20) The old transmission was not properly calibrated for the 3.73 rearend. Gear Star installed a new AC Delco speedo gear for just that reason.

21) One of the major upgraded was the switch to this Yank 10 inch converter that’s locked at highway speeds, but at wide-open throttle in fourth gear, Gear Star’s transmission denies converter lock-up until the redline, acting like a de facto fifth gear.