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Toyota C-5X Transaxle Myths and Mysteries
I have done extensive work on rebuilding and modifying the C-5X series of transaxles. I have very little experience with the E-51 as used in the AW11 Supercharged MR2s. I have heard that there are LSDs and other gear sets for the E series, but I have no direct experience with them and no additional information on them, so I'll concentrate on what I do know, the C-5X series. Also, my experience has been with North American Distribution, so there may be variances overseas that I'm not aware of.
The C-50 transmission first came out in the early 1980s in some of the FWD Toyotas. It is very similar to the C-40 transaxle (4-speed) and shares some components. The C-50 was shipped with two different final drive ratios (that I know of): 3.722 and 4.311. It was also made in two different shifter configurations: one for the FWD cars (Corollas) and another for the RWD cars (MR2). The RWD units all had the 4.311 final drive. The C-50 has evolved through the years and has had spin-offs like the C-150. The C-52 is a slightly newer C-50, still sharing many components. The C-56 is one of the latest variants, again sharing parts, but having several upgrades and changes along the way. Even the C-60 (6-speed) used in the Celica is of the same family.FWD vs. RWD
The two transaxles are almost identical except for the shifter linkage. The FWD units have the shift selector shaft exiting on the rear (differential side) of the case because in a FWD car it would be closer to the firewall. (The firewall is in the rear of the engine compartment in a Corolla, Tercel, and Paseo.)
The RWD units (MR2) have the shift selector shaft exiting on the front of the case, again, closer to the firewall. (The firewall is in the front of the engine compartment in an MR2.)
Both of these configurations allow the shortest distance from the shift selector shaft to a cable connection, through the firewall, and to the shifter.Identifying C-5X Transaxles
When you are shopping for a used transaxle for your car, look closely at the shift selector shaft. When looking at the transmission from the "left side" (small case end towards you, bell housing away from you, differential/axle stubs to your right), a FWD transaxle will have the selector shaft exiting the case on the right, just above the differential. A RWD transaxle will have the shaft exiting on your left. (This only applies to a C-50/C-52.)
A C-50 and a C-52 look very similar and they are very similar. They share many parts. The key factor is that a C-50 has a boss or hump for the starter motor on the front side of the transmission case. (The front side is away from the differential, or if looking at one on a car, the exhaust side of the engine.) On the other hand, the C-52 has two starter bosses, one in the front and one in the back. The normal 1.0 kW or 1.4 kW starter can be bolted in place on the front position under the exhaust manifold. The 1.4 kW starter from a supercharged MR2 can be bolted to the rear boss. I have seen C-52s that have the bolt holes already drilled and tapped for the starter in the rear position and I have seen others that need to be drilled and tapped but the mounting points are there.
A key advantage to the rear position is that if you bolt the starter to the rear side (or intake side) of the engine, it opens up a large space to add a turbo. You can still fit a turbo with the starter in the front position but the starter will only last about 3000-5000 miles until the varnish has melted off of the windings and then you get a no start condition. (Guess how I know?)C-50/C-52 Differences
Every C-50 and C-52 that I have seen that came from an AW11 MR2 had the 4:311 final gearing. I have seen FWD units with both the 4:311 and the 3:722 final gearing. The C-52s have some stronger parts. The 1-2 shift fork was upgraded and is interchangeable. The C-52 has a larger diameter input shaft where fourth gear rides on its bearing and hence has a different bearing and gear. Syncros have been upgraded over the years and the later ones are much better. The later 1-2 syncros can be directly dropped in to an early C-50, but third and fourth require some additional parts to make the swap. I don't think the fifth gear has ever changed.The C-150 Transaxle
Be wary of the C-150. At first glance it appears very similar to a C-50 and to the untrained eye, it could be passed off as one. Other than a few small bolts, this cousin to the C-5X series shares few parts. This transaxle is slightly shorter than a C-5X and has a smooth finish to the case and bell housing. (The real C-5Xs have strengthening ribs down the bell housing.) The C-150 is smaller and lighter weight, all the gears are a little narrower than the C-5X so the input and output shafts are shorter, and the differential is a puny little paper weight.Using a FWD Transaxle in a RWD Car
Or, better stated, "converting a FWD transaxle to RWD setup by moving the shift selector shaft."
First, if you can locate the correct transmission, do it! If you cannot, the process can be done, but you are better off just rebuilding your transmission.
In order to do this, you will need the Genuine Toyota "Big Green Book." You will also need some gear pullers, some bearing drivers, and a very good 0-15 in-oz dial-type torque wrench. (Read "expensive 0-15 in-oz torque wrench" and, yes, that does say inch-ounces.) You will need pretty much all the tools that are stated in the BGB about rebuilding a transmission, along with a selection of differential pre-load adjusting shims.
Let's presume that you have a good C-50 FWD transmission. You will also need a RWD C-50 transmission to get the case center section, shifter selector shaft, and housing cover. You will disassemble the FWD transmission and the RWD transmission. I could go through all the details but it's all in the BGB. When you get the first transmission apart and the center section off, you may think that you're almost done. Tear down the second transmission, swap cases and you're finished, right? There is a slight catch.
It's not that simple. The center section and bell housing section also make up the differential housing and each half has a bearing race for the differential. Because you are going to be using parts of two cases that weren't originally used together, you must re-set the pre-load of the differential. (If you chose to skip this step, I hope you have alternate transportation because your "new" transmission won't last long.) The pre-load is adjusted by selecting shims that sit under the outer bearing race of the differential. This is normally done by hand at the factory and now because we are using different case halves, we will have to adjust it again.
The procedure is given in the BGB, but I'll outline it here. First, tear down the entire shifter mechanism from the gears, then remove the shifters, then remove the input shaft and output shaft as a set. Now you just have a differential sitting on the bearing in the bell housing case. You would now assemble the new case center section with no gears, just an empty shell. You put the case all together, bolts and all, and check the pre-load with the torque wrench and a special adapter. If the torque is too low, or too high, you tear it all back down and change the bearing shim. You continue to assemble, measure, tear down, assemble, measure, etc. until you get the correct pre-load. It still takes me at least three to four cycles to get it "spot on." Once you have it adjusted correctly, you can tear it down again, install the input and output shafts, shifter rails, shifter forks and such, then assemble the center section. Finish up with the rest of the parts and you're done... finally. Now you can put it in your car.
There are several ratios available, from 3.56:1 to 5.166:1. Toyota used the 4.312:1 and the 3.722:1 in production vehicles for the US and I'm told that the 3.56:1 was used in production somewhere, but I have yet to see one in a 5-speed transmission. I have seen it in a C-40, but due to the output shaft differences, it won't fit a C-5X. TRD also makes some gear sets for the C-5X transaxles but they are cost prohibitive.
The addition of an LSD is excellent for the track and street. I personally don't like clutch-type units and am biased towards the Quaife or TRD helical gear units. They both give phenomenal performance.
Installation of an LSD is not an easy task and requires complete tear down of the transmission as outlined above and it is detailed in Toyota's BGB. This is not a task for a newcomer and only the most experienced shops can perform this type of work. If you would like a quote on the installation of an LSD in your Toyota transmission, contact us.
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