Improving the 2nd to 3rd Shift 1981 to 1990 722.3 Mercedes Auto Transmissions — Transcript

Full transcript

1. 0:04This is the valve body out of a Mercedes
2. 0:06722.3 transmission. And I want to talk
3. 0:10in this video about doing one of the
4. 0:12most common upgrades that you'll hear
5. 0:14about on the internet. Now, people call
6. 0:17this upgrade the K1 upgrade, and I'm
7. 0:20going to disagree.
8. 0:23This is the K1. This is commonly
9. 0:26referred to as the K1 inside these
10. 0:29transmissions. So, you really can't call
11. 0:31this a K1 upgrade. This is the upgrade
12. 0:34we're going to be talking about here.
13. 0:35This is a part that goes into the valve
14. 0:38body. And this is called an accumulator.
15. 0:40So, what I'm going to do is I'm going to
16. 0:43always refer to this as the K1
17. 0:46accumulator upgrade. You're looking at
18. 0:49the original setup here, the original
19. 0:52accumulator, and this is the upgrade
20. 0:54right here. Now, some of the later
21. 0:57transmissions in the early 90s already
22. 1:00had the upgrade in them. And you can
23. 1:02recognize the difference between the
24. 1:04upgrade has a black plastic end cap and
25. 1:08the original has kind of, you know,
26. 1:10yellow.
27. 1:12So, what's the difference here? Take a
28. 1:13look right here. Look at the big spring.
29. 1:16The big spring on the upgrade is shorter
30. 1:19and has thicker coils. The center spring
31. 1:24looks very close, but if you look, you
32. 1:27can see a little bit difference in the
33. 1:28gap. The length is the same, but there's
34. 1:30a difference in the gap. And then look
35. 1:33at the end spring, which goes down into
36. 1:36the housing of the accumulator. Height
37. 1:39is a little bit smaller, but you can see
38. 1:40it has less coils. So, there it is,
39. 1:43folks. This is something that you can do
40. 1:45yourself. It's not real difficult and
41. 1:49you can actually do it without removing
42. 1:51the valve body or dropping the
43. 1:53transmission. Next, let's talk about
44. 1:55where this is located. The valve body
45. 1:58has lots of covers on the front and the
46. 2:03back. Now, in as far as orientation,
47. 2:06this would be the front of the valve
48. 2:08body. So, the bell housing of the
49. 2:11transmission would start right about
50. 2:13here. You would be looking at this. This
51. 2:15would be the left side. And you're
52. 2:17looking for this square plate right
53. 2:19here. People say it's a square plate.
54. 2:21You're not looking at the square plate
55. 2:22in the back here. You're looking at the
56. 2:25lower left side square plate in the
57. 2:29front of the valve body. So, I'm going
58. 2:31to go ahead and remove these four
59. 2:33screws. And we're going to pull out that
60. 2:35assembly. You can see there's not a
61. 2:37whole lot of pressure.
62. 2:41And then you're going to remove the
63. 2:42green piston right there. Notice the
64. 2:45orientation.
65. 2:47And you'll pull the spring assembly out.
66. 2:50And notice the orientation there. You
67. 2:53can see this goes in to the piston.
68. 2:59And inside is where that smaller spring
69. 3:02is.
70. 3:04So that's your orientation on an
71. 3:06original K2 accumulator spring assembly.
72. 3:09If you don't already know, let's take a
73. 3:11minute and talk about the purpose of
74. 3:12this upgrade. It's to improve shifts
75. 3:16between second and third gear,
76. 3:19particularly if there's a delay or what
77. 3:21some people call flaring between two and
78. 3:24three. This is a very common issue on
79. 3:26these transmissions. You'll go along,
80. 3:28it'll shift in a second, and then
81. 3:31between second and third, you'll kind of
82. 3:33feel this a little bit of engine
83. 3:35acceleration
84. 3:37before it engages. Well, what the
85. 3:39accumulators do, particularly this
86. 3:41accumulator inside this valve body,
87. 3:45it delays the engagement
88. 3:49between second and third.
89. 3:51So, if you didn't have accumulator,
90. 3:54it would be abruptly like that when it
91. 3:57shifted. So, the accumulator
92. 4:00softens or transitions that shift to
93. 4:04something that's much more pleasurable,
94. 4:06if I could use that.
95. 4:08So, what they've done is they've
96. 4:09modified the spring pressure. And I'm
97. 4:11not going to get into all the specifics
98. 4:13of the engineering of these springs, but
99. 4:15that's basically what they did. They've
100. 4:17modified the spring pressure inside the
101. 4:19accumulator
102. 4:21to not delay so long.
103. 4:25So, you'll eliminate that flaring and
104. 4:27you're going to say, "Yes, that's
105. 4:29exactly the problem I have. I'm going to
106. 4:31put this, you know, K1 accumulate
107. 4:34upgrade my transmission. all my problems
108. 4:36will be solved. Well, uh, not so fast.
109. 4:39We'll get into that a little bit later.
110. 4:41Along with the differences in the
111. 4:43springs, I think they improved
112. 4:46these plastic pieces and the way they
113. 4:48connect and snap together.
114. 4:50These two early style, they just had a
115. 4:53little nib on there and they just pop in
116. 4:55here and they come out. It's It's not a
117. 4:58big issue because once everything's
118. 5:00compressed, you're okay. But trying to
119. 5:02put it all together and keep it together
120. 5:04while you insert it is a different
121. 5:06matter. So, we're going to do the new
122. 5:09one. Uh, this is the small spring that's
123. 5:13going to go right in here. Now, I've
124. 5:14already cleaned this. I've inspected the
125. 5:16seals. The seals are still soft, so I
126. 5:20can reuse them. And I'll drop that
127. 5:22spring in. Just like that. Okay. Now,
128. 5:24we're going to assemble this.
129. 5:30And it doesn't matter which end of this
130. 5:32which spring goes where. And now we have
131. 5:34to press this together.
132. 5:38This gets a little tricky. You have to
133. 5:40press it down. And you have to make sure
134. 5:42it's lined up properly before you push.
135. 5:46And then you want to push straight down.
136. 5:50And when you go all the way down, you'll
137. 5:52feel it snap in.
138. 5:55And now it's locked in place. We're
139. 5:57ready to install it back into the valve
140. 5:58body. And then now we'll just install
141. 6:00the spring assembly into the piston. You
142. 6:04make sure you know you'd put that
143. 6:05smaller spring down inside. And then I'm
144. 6:08going to just take a little bit of
145. 6:09transmission fluid and we're going to
146. 6:12lube these seals.
147. 6:15And then we're going to slide it in.
148. 6:21And then I'll get the plate ready here.
149. 6:24You can really only get this plate on
150. 6:26one way.
151. 6:28and then hold that in.
152. 6:32Get this first screw started. I'm going
153. 6:36to run it in by hand till I get close.
154. 6:41Okay. I don't think you need to see me
155. 6:43tighten down four screws. But the torque
156. 6:47for these is 8 Newton meters. So, be
157. 6:49careful. Do not over torque them. They
158. 6:52are going in to aluminum threads. Once I
159. 6:56tighten those down, you're finished. So,
160. 6:58that's a fairly simple upgrade. But what
161. 7:01if you do this on your transmission, put
162. 7:04it all back together, you're all
163. 7:05excited, you get in the car, you go down
164. 7:06the road, and it's still flaring between
165. 7:08second and third. How could that be? You
166. 7:10were told that this would fix your
167. 7:12problem, but it didn't. Why? Some of you
168. 7:14are going to say, "Hey, can't just
169. 7:16adjust the modulator. That's going to
170. 7:17solve all your problems. I see this a
171. 7:19lot." Remember, these transmissions are
172. 7:21old.
173. 7:23really old and they're getting tired.
174. 7:25And I know people try to solve all the
175. 7:27problems by, you know, adjusting the
176. 7:29modulator back and forth and thinking
177. 7:31they can change the pressure and get rid
178. 7:33of the flaring. What happens is if you
179. 7:35have flaring in just one gear, you play
180. 7:38around with the modulator, you may
181. 7:40affect that one, but another one might
182. 7:41be slipping or jerking. And when it gets
183. 7:44to the situation where you've got a
184. 7:46pronounced flare between second and
185. 7:48third only, it's probably not modulation
186. 7:51pressure. So, if you've completed this
187. 7:54upgrade and it's still flaring between
188. 7:55second and third, my humble opinion,
189. 7:58it's going to be a problem with this.
190. 8:00Okay, this is your K1
191. 8:03and it has clutch discs in there. Now,
192. 8:05if the clutch discs are worn, well, you
193. 8:09can put every upgrade in the book in
194. 8:11there and it's still going to flare.
195. 8:12Also, people don't mention this very
196. 8:14often, but there are two lip seals in
197. 8:17here. And if these lip seals are worn or
198. 8:21even cracked, you're going to be losing
199. 8:24pressure in the K1 and it won't fully
200. 8:27engage
201. 8:29the clutches. So, what you're looking at
202. 8:32here is a cutaway. And I'm going to
203. 8:34briefly explain where this K1 is
204. 8:37located, what happens when it shifts
205. 8:39between second and third.
206. 8:41So, a quick overview of what's going on
207. 8:43here. This is the B2 piston. This is the
208. 8:48B1 piston.
209. 8:50This is the B2 brake band.
210. 8:54This in here is the B1 brake band. And
211. 8:58the drum down in there is the K1.
212. 9:02This was the K1. Okay? And the drum down
213. 9:04here is the K2. So when you're going
214. 9:08along in second gear, watch this.
215. 9:12Both of the brake bands lock onto the K1
216. 9:16and K2 drum. Now, when you shift between
217. 9:20second and third, this stays engaged,
218. 9:24but this piston comes out, releases the
219. 9:27brake band, and at the same time,
220. 9:31pressure builds and closes the clutches
221. 9:34together. So imagine what happens if
222. 9:38you're losing pressure in the drum or
223. 9:41your clutch packs are worn. You're going
224. 9:43to get the delay between second and
225. 9:46third. So don't always assume that doing
226. 9:50this K1 accumul upgrade is going to
227. 9:52solve your problem.
228. 9:54[Music]