TH350 rebuild tech
(Minor clean up.) |
(Minor clean up.) |
||
| Line 64: | Line 64: | ||
The first item to go in the case will be the low/reverse apply piston. | The first item to go in the case will be the low/reverse apply piston. | ||
| + | |||
Its function is for oil to force it towards the front or bell housing side of the trans, applying the low/reverse clutches. This allows reverse when applied simultaneously with the direct (high gear) clutches, and allows manual low gear when applied with the forward clutches. Manual low gear creates engine braking on deceleration. The low/reverse clutches do not apply in automatic range 1st gear. The low sprag (low roller clutch actually) causes first gear when only the forward clutches are applied. | Its function is for oil to force it towards the front or bell housing side of the trans, applying the low/reverse clutches. This allows reverse when applied simultaneously with the direct (high gear) clutches, and allows manual low gear when applied with the forward clutches. Manual low gear creates engine braking on deceleration. The low/reverse clutches do not apply in automatic range 1st gear. The low sprag (low roller clutch actually) causes first gear when only the forward clutches are applied. | ||
| Line 162: | Line 163: | ||
For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" to allow for one extra friction and steel plate for a total of 5 frictions, and 5 steels in the directs. This can be accomplished on a brake lathe. | For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" to allow for one extra friction and steel plate for a total of 5 frictions, and 5 steels in the directs. This can be accomplished on a brake lathe. | ||
| − | Stock measurement is 0.835", machine the piston to 0.700". Ideally you would | + | Stock measurement is 0.835", machine the piston to 0.700". Ideally you would preassemble, and check clearance using a 4 clutch pack. Measure the additional thickness of the extra friction and steel, then cut the exact amount needed to leave you the exact clearance you desire. Rule of thumb on most auto trans friction clearances is 0.010" clearance per friction. So a 5 friction direct setup would work great with 0.050" to 0.070" clearance. It will work with less, no less than 0.040", and will work with quite a bit more, but excessive clearance can result in delayed engagement, busted lip seals, and unsatisfactory shift quality. |
If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. You can leave out center cushion seal if dual feed is used. | If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. You can leave out center cushion seal if dual feed is used. | ||
| Line 219: | Line 220: | ||
Internally dual feeding is preferred because it leaves out the additional gasket and eliminates that one extra possibility for a pressure loss resulting in burnt 3rd gear clutches. | Internally dual feeding is preferred because it leaves out the additional gasket and eliminates that one extra possibility for a pressure loss resulting in burnt 3rd gear clutches. | ||
| + | |||
All transbrakes will require dual feed of the direct clutch, as well as many manual valve bodies. | All transbrakes will require dual feed of the direct clutch, as well as many manual valve bodies. | ||
| Line 255: | Line 257: | ||
Forward clutch pack clearances can be tighter than usual; however it must have some clearance. If too tight it can creep in neutral. | Forward clutch pack clearances can be tighter than usual; however it must have some clearance. If too tight it can creep in neutral. | ||
| − | Pay attention to this polished stub of the input shaft, it goes into the bushing that is in the end of the output shaft. It is a high wear area. Be sure it is smooth. Minor scoring can be smoothed down. | + | Pay attention to this polished stub of the input shaft, it goes into the bushing that is in the end of the output shaft. It is a high wear area. Be sure it is smooth. Minor scoring can be smoothed down. May consider use of teflon bushing, only a lubrication passage, no pressure, no lateral loading. |
[[file:TH350forwardwear.jpg]] | [[file:TH350forwardwear.jpg]] | ||
Your Privacy Choices