Rebuilding an NG3 (hopefully useful info for other trannies as well)

[BDA]

I've been working on this over several weeks and it occurred to me that rebuilding the tranny may be more common than I thought, but if you've never done it before and you're thinking your tranny needs some help, this may be helpful. Before you dive into your tranny (unless you want to rebuild it to have new parts rather than fix something about it), you should make sure that your clutch and linkage are in good shape as your problems may lie in either of those.

If you've decided to take the dive, be brave. I did not find it as difficult as I thought I would. Note that I didn't refresh EVERYTHING in the box. Some specific parts are NLA or difficult to find. I figured discretion is the better part of valor so I kept it simple and didn't get into the diff or the shift forks.

I didn't delve into any of the 3xx series trannies but the NG3 appears to be very similar to them so I suspect that there are enough similarities that my experience might be helpful to you if you're working on a 3xx series box.

I can't attach a .doc or .docx file and it's too long to include in a single post so I'll break it up into smaller bits.

[BDA]

I have recently finished rebuilding my NG3 transaxle which was my first attempt at rebuilding a transaxle or transmission. This is my attempt at filling in some of the details that may not be explained fully in the manuals and to help a neophyte get the courage to attempt their own transaxle rebuild.

Rebuilding a transaxle really isn't as daunting as it might appear. It isn't over simplifying it too much to say that a transaxle or transmission is two stacks of gears. The object is to put them back in the same order and orientation as you took them out only this time with the new parts you've sourced. It isn't that difficult. Keep in mind that my experience only relates to the NG3 transaxle. I won't address the end cover except to provide the seal number for the cross shaft seals. There are a few ways the end cover is built dependent on the type of linkage and I would only be able to address the end cover as Richard Winter provided on his NG3s. They are simple enough that most shouldn't have a problem with them.

To my surprise, dealing with suppliers was more difficult than rebuilding a transaxle for the first time. I suspect that some of my frustrations would be less likely with the 3xx series transaxle that most of us have but some of my experiences might still be useful to you if you embark on rebuilding a 3xx series tranny.

There are two NG manuals available from the Lotus Europa Central Documentation page (http://lotus-europa.com/manuals/). The information is essentially the same but there are some differences so it would be useful to familiarize yourself with both. One, which I'll refer to as manual #1 in this post, (http://lotus-europa.com/manuals/misc/ng.pdf) is I think a scan of a manual translated for American Motors when they were selling Renaults. The other one, which I'll refer to as manual #2, looks even rougher (http://lotus-europa.com/manuals/misc/MRBVNG.pdf) and seems like it could be a section from the Fuego manual since part of it is concerned with taking the tranny out of the car, fitting the clutch, etc. but it is still very useful to have as there are details spelled out in it that are not in manual #1. Unfortunately neither of these manuals are searchable for text.

Different types of NG3 transaxles

There are two different types or series of NG3 transaxle. The manual #I referred to them as "1st Assembly" and "2nd  Assembly.” Manual #2 refers to them as 1st type and 2nd type. I'll refer to them as 1st type and 2nd type.

There are several differences between the two types. One spelled out in both manuals is the difference in the distance between 2nd gear on the secondary shaft and the next snap ring groove in the shaft.
1st type: 49.5mm
2nd type: 33.5mm

Another difference (noted in manual #2) is the thickness of the snap rings and splined washers.

1st type: 1.9mm snap rings; 1.5mm splined washers
2nd type: 2.8mm snap rings; 2.2mm splined washers

Another difference (noted in manual #2) is that the 1st type secondary shaft has straight splines where the 2nd type has helical splines. The picture of the helical splines in manual #2 doesn't help me understand the difference so I'm of no help with this difference but I would expect the difference to be obvious.

Yet another difference noted in manual #2 is that the 2nd type has an oilway that apparently supplies more oil to the differential carrier bearings and includes a deflector between the finned adjusting nut and the bearing as well as a different seal design. It appeared to me that my case had that oilway even though I had a 1st type transaxle.

Note that none of the information on the aluminum identification tag (with serial number and suffix number) that your transaxle hopefully still has will tell you which type (1st type or 2nd type) of NG3 transaxle you have but it will help you learn your gear ratios and final drive ratio. Both manuals give details about gear and final drive ratios for the different suffix numbers).

As I previously stated, my NG3 was of the 1st type and this entire document pertains to that type of NG3. I will not address the 2nd type at all but much of what I will address is applicable to both types.

One of the effects of having one type or the other is the order in which reverse gear (with hub), a splined washer, and a snap ring are assembled on the secondary shaft. It turns out that those components only fit one way so that should alleviate any concern that you could assemble those parts in the wrong order.

Lastly, there are two different sets of synchros. Actually, the 1 and 2 synchros are Renault parts and are the the parts that vary between the two different sets and the 3, 4, and 5 synchros are the same for all NG3 boxes and, as noted in manual #2, are Borg-Warner units. (I don't know if these synchros can be sourced from Borg-Warner directly.). I suspect strongly that the 1 and 2 synchros are different between the 1st and 2nd type boxes. I don't know that for sure. If true, the 1st type box is the most common according to Michel at Alpine-America.

Tools

There aren't a lot of special tools required but there are a couple that will make life a lot easier.

In order to take the tranny apart, a 32mm crow foot wrench is almost essential in taking the speedo gear/nut off the secondary shaft. It's also very handy to ensure that the speedo gear/nut is torqued properly. You will almost certainly have to grind the thickness of the crow foot wrench to fit the flats of the speedo gear/nut.

The second tool which is very useful is a pair of “backward” pliers. By this I mean pliers with knurled surfaces on the outside rather than the inside. They are usually sprung and when you squeeze the handle, the jaws open. These are pretty much required for spreading the snap rings as the snap rings are not the ones you generally see with holes in them. Snap ring pliers you normally see will not work. Speedwox, Lisle, and Proto make several sizes of pliers designed for the job and are available at Amazon and Ebay. Search for “lock ring pliers”.

Of course a wrench to adjust the finned adjusting nuts is required. r.d. enterprises sells one foe the 3xx transaxles and it may work on the NG3 but I can't be sure as that nut is a bit different from those found on 3xx transaxles. I used a motorcycle clutch tool. They are inexpensive and can be had from ebay, Amazon, and I'm sure many other places.

A long piece of angle iron or flat bar drilled to be bolted to the bell housing or the transaxle-to-bell housing interface to resist the torque when tightening up the primary shaft nut and secondary shaft speedo gear/nut is very helpful.

[BDA]

Reading the manual

I won't go through either manual step by step, I will emphasize points and add some hints that will hopefully be useful. Here is a list of things that should be replaced regardless. For example, roll pins, planet wheel shaft retaining collar, clutch housing bearing, all snap rings, and primary shaft nut. Unfortunately, some maybe all, of those items are made of unobtanium such as the snap rings, planet wheel shaft retaining collar, and clutch housing bearing. I didn't get into the differential so I didn't have to worry about the retaining collar. I would suggest not going into the differential unless you know you need to.

Some terminology
LOCTITE SCELBLOC = blue Loctite
LOCTITE FRENBLOC = red Loctite

Disassembly

Years ago, Richard Winter told me to lock the transaxle by selecting two gears at one time on two different gates (1 or 2 and 3 or 4) to loosen the nuts on the primary and secondary shafts. I have done this in the past but for whatever reason, I was unable to do that when I rebuilt my transaxle. This time I used an inexpensive screwdriver (the gears will chew up your screwdriver) to lock the gears on the two shafts.The nut on the primary shaft and the speedo gear/nut were assembled with red Loctite so heat may be needed to disassemble them. If so, this will of course destroy the nylon speedo gear. I don't know if replacements are available, I doubt it, so it would be time for either an electronic or GPS speedo. In addition to the Loctite, the nut on the primary shaft was likely peened to give added assurance that the nut won't back off. If so, that will obviously have to be straightened so the nut can be loosened.

Take the speedo gear/nut, washer, 5th gear, and spacer off the secondary shaft and what I'll call the 5th gear assembly (nut, washer, hub and sliding gear, spring, synchro, gear, bearing and bushing) off the primary shaft. Take note of how the spring seats with the synchro. Also note that inside the 5th gear, there is a needle bearing with a plastic cage that runs on a bush. You can now open up the case.

Once the case is opened up (I advise taking several pictures of the opened box. Take more than you think necessary and from more different angles than you think necessary. Having these will likely give you added confidence when you reassemble the box.) and the 5th gear from the secondary shaft and hub and sliding gear and synchro has being taken off the primary and secondary shafts, the main task is to disassemble and then assemble the secondary shaft. Since this is really just a stack of gears (with snap rings, splined washers) with synchro mechanisms. So, the order and orientation of these parts is your main concern. Taking pictures often during disassembly (more than you think necessary and from more angles than  you think necessary) will pay dividends. Taking pictures from several angles may seem redundant but I advise it anyway since you really don't know which angles you'll need till you find you don't have it!

Be very careful spreading the snap rings. Don't expand them any more than is needed to get them off or back on the secondary shaft. They are not made of spring steel as I expected. Manual #1 suggests using pliers to hold the other side of the snap ring when spreading the ends of the ring to stabilize the ring. This is a very good practice. After getting the snap ring out of the groove using the side rather than the tip of some needle nose pliers was helpful to keep the snap ring stabilized. They aren't particularly fragile but they can be bent beyond the yield point and they can be bent back but since new ones are not available, it's better not to take a chance in breaking one. If you do break one, it's not the end of the world as there appear to be reasonable substitutions (see below).

I recommend that as you take gears off the secondary shaft, that you keep them together in some logical grouping.  Loosely zip tying each of these groups will help preserver their order and orientation. Keeping them in the zip tie when you wash the parts will eliminate any anxiety about the orientation of the parts but relax because there are only a few parts whose orientation is not easily determined. However, I think it would make a good practice and it will give you peace of mind when you reassemble the transaxle.

There are spring loaded rollers in the reverse hub which could possibly fly out after you take off the 4th gear and synchro. It's more likely to happen when taking the reverse hub and sliding gear off. Be ready to catch them in either event should that happen. Manual #2 has some good illustrations to help you orient the rollers and springs correctly.

I was rebuilding my transaxle because I was grinding going into 1st gear. I expected to see noticeable wear on the 1st gear syncho at least but there was no noticeable wear on any of the synchros. When I compared appearance of the old synchro in the hub to the new, the old synchro actually sat a very small amount more proud in the hub than the new! That was unexpected since if it was worn, it should sit deeper in the hub! On the other had, the new synchro did seem to grip the hub (both dry) a little better than the old one when I moved them by hand which was expected. My point is that visual examination of the synchros may not tell you anything. My advice is to change them all regardless what the old ones look like.

hub & sliding gears
Hubs and sliding gears are lapped together and it is best to replace them in the same orientation to each other as when they were taken out. Make note of marks on the edges of the hubs and sliding gears, make small scratches, or put paint marks on them so that the orientation can be reproduced. You want your reference marks not to be washed off when you clean your parts.

The outer races of the differential carrier bearings can be gently tapped out with a punch and a small mallet. The seals in the differential ring nuts can be pressed on a vice with an appropriately sized socket to push the seal out and something to space the ring nut from the vice jaw so the seal can come out (two pieces of scrap steel or aluminum that are the same thickness for example).

[BDA]

Reassembly

Gently tap the outer races of new differential carrier bearings into the case halves. The dimensions of the outer races of the differential carrier bearings should be the same but it's best to keep the outer race together with its bearing. I don't remember which side of the differential carrier has which bearing but with the case half containing the gear selector shafts sitting on a bench, the differential carrier is installed such that the ring gear teeth are pointing down or into the case half. But you already took a picture of this so you'll know, right?

Assemble the two cases with the differential carrier torquing all the case bolts properly. Adjust the differential ring nuts so that the proper drag is felt and the bearing preload is correct. Then split the case again.

Assembling the secondary and primary shafts are pretty much the reverse of taking them apart. Before assembling the parts that live in the end cover (5th gear assembly on the primary shaft and the 5th gear, spacer, washer, and speedo gear/nut on the secondary shaft), fit both shafts in the case half with the gear selector shafts and make sure all the gears mesh and all the available gears (R - 4) can be selected using the shift forks.

Apply the sealant to the edges of the case, install the differential, the primary and secondary shafts and then torque the case bolts. Adjust the ring/pinion backlash by loosening one finned adjusting nut and loosening the other the same amount till the prescribed backlash is achieved. Again check that you can select all available gears (R – 4) using the shift forks.

After assembling the rest of the primary and secondary shafts and torquing the primary shaft nut and the secondary shaft speedo gear/nut, bolt the bell housing and end covers on with your choice of sealant. And check that all gears (R – 5) are selectable one final time before the transaxle is installed into the car. Before bolting on the end cover, put the transaxle in neutral, cock the end cover and the cross shaft so that the shift finger on the cross shaft is in the shift forks and the box is still in neutral. After the end cover bolts are torqued, check again to make sure that all gears (R – 5) are selectable.

Parts

I've tried to use “generic” part numbers but because I got most of the parts from 123Bearing.com, their numbers are used below except where noted.
Bearings
Secondary shaft pinion roller bearing   RNU10552S01-SNR
Secondary shaft double roller bearing  FC10893-SNR
Primary shaft roller bearing                 RNU10868S01 SNR
Primary shaft double ball bearing         GB10890S01-SNR
Differential carrier bearing                   30207-TIMKEN
Differential carrier bearing                   30207-37F-ASFERSA (123Bearing) or
                           7703090179 (Renault 16 Shop)

Seals
Seals are standard. The designations below are from 123Bearing. They would likely be available from a local bearing supply house. 123Bearing also sells O-rings. I measured the OD of the groove in the finned adjusting nut and used that dimension to order an O-ring. The ring I got was way too big so I won't include the part number for it. Since my O-rings were not leaking, I just reused them and I smeared Hylomar on the threads of the finned adjusting nuts when I installed them.
Output shaft   OAS-26X42X10-NBR
Cross shaft   CB-16x22.75x4.20-NBR

Suppliers
As I stated at the beginning, I had much more trouble finding parts than actually putting the transaxle together. I got most of the bearings and seals from 123Bearing. Their service is excellent. 123Bearing did not have the larger of the differential carrier bearings so I got it from Renault 16 Shop. Their service was also excellent and very personal. There was still one bearing that I couldn't find at either of those places. I looked all over. I found several places that listed it but they did not have it. Some of the places did not return my email or phone calls. One place that did was in Ukraine but they didn't have it. I finally found a guy, Olivier, in Canada who had contacts in Europe (Olivier runs a shop called Atelier MAHOA) who was able to get it for me. I was his first US customer and everything went off without a hitch. I bought my synchros from Michel at Alpine-America. I bought them before I opened up my transaxle so I had no idea which type I had. Michel said he sent me synchros for the most common type of NG3 and they turned out to be the correct synchros. I asked him to get me some bearings that neither 123Bearing nor Renault 16 Shop had and I never got them so I found his service to be mixed to say the least. If you decide to use him as a supplier or for technical assistance, I recommend sending him emails in both English and French (translate.google.com is your friend). He will answer his phone and he will return phone messages, but somewhat inconsistently. His English (really Frenglish) was difficult for me to understand so I tended to use email more often.

I included McMaster-Carr because they list heavy duty external retaining rings that would appear to make a good substitute for a Renault snap ring in the event you break one. Search for “metric snap rings.” They are listed in the sizes needed (30mm and 32mm) and they are a 2mm thick. You'll have to sand them down 0.1mm.

123Bearings              https://www.123bearing.com   (646) 712-9672
Renault 16 Shop        https://www.renault16shop.com
Atelier MAHOA           https://www.facebook.com/ateliermahoa/   olivier@ateliermahoa.com
McMaster-Carr           https://www.mcmaster.com
Apline-America          https://www.alpine-america.qc.ca/

Sealing compound
I have some Permatex gasket maker formulated for synthetic oil and some gasket maker formulated for gear oil. Since I planned on using synthetic gear oil, I consulted them and they recommended Permatex  #81182 Gear Oil gasket maker. I previously had a friend of mine look at the innards of my transaxle and he used a Porsche sealant when he bolted it back together. Unfortunately, I don't know the name of that stuff but a Porsche dealer should be able to help you with it. It is very thin and dries hard. I have to say I was impressed with both the Permatex and the Porsche sealant.

[SwiftDB4]

Thanks a lot for posting everything. Rebuilding an NG3 is a learning experience for sure. Especially thanks for the parts numbers including McMaster Carr snap rings!

[BDA]

Thanks for chiming in, Swift! I know you’ve been down this road and I was hoping you’d find this and if I forgot something or got something wrong, you’d catch it so I guess I did alright with the parts I covered.

I invite any corrections or additions everyone.