Blooze Own: An F355 Six Speed N* Build Thread (Page 100/126)
fieroguru MAR 18, 10:44 AM

quote
Originally posted by Bloozberry:
Bear in mind that the Cobalt SS uses the F35 five speed transmission, but it has the same tripots as the G6 F40 six speed transmission.



The F40 and F35 both use 27 spline for the differential to tripod interface, but the design of the actual tripod housings are indeed different. The F40 one is kinda fiero shaped where it is a formed housing, but the real differnece is in the diameter of the rollers within the tripod housing - they are much larger on the F40 one. The F40 also uses 1 male and 1 female tripod. Here is a picture of the female one:


It looks like the F35 tripods are of a similar design as the Equinox and other GM 5 speed auto tripods.

Where the ability to interchange axles for an F40 hits a road block is normally on the tripod side. If the housing uses larger rollers (F40) and the roller housing has a unique spline count, then it becomes difficult to either find a tripod roller setup that fits the housing, or a longer (or shorter) axle shaft with the same splines for the roller housing. As far as I know, there is no other compatible roller housing for the G6 tripods so you have to find an axle that will slide into the G6 roller housing. The G6 axles switched splines on the actual axle shafts from 33 to 34 or 34 to 33 and the 33 is a no-go as far as finding other GM axles. The 34 was a possibility, but when my G6 axles showed up, they were both 33 so I never got a chance to play with a 34 spline version.

I am hoping that the tripod rollers on the Cobalt axles are the same as some other GM applications.
kennn MAR 18, 02:21 PM
Thank you Blooze, Guru and all for this discussion. My combo is Gen 1 ZZ3 to F40., shifted so far toward the driver's side that the F40 interferes with both the chassis and cradle on the driver's side. That issue, resolved and set aside, I find it curious that the Cobalt axle has 24 splines. I have a Cobalt SS axle, a Saab 9-3 axle and a G6 (male end) axle. All have 27 splines and all fit my F40. What am I missing? Can both 24 and 27 splines engage in the same trannie?

Somewhat confused in Arizona,

Ken

------------------
'88 Formula V6
'88 GT TPI V8

[This message has been edited by kennn (edited 03-18-2014).]

Bloozberry MAR 18, 02:37 PM

quote
Originally posted by Danyel:
I am REALLY reading this carefully



Thanks Danyel for following along. Hopefully a few of us can pool our information together and de-mystify what parts can be used. As I mentioned, I'll summarize my findings soon.


quote
Originally posted by Will:
The new ones may be made out of the finest Chinese lead...



Yeah... these were in fact made in China, but it's hard to know the origin of the part in advance. I guess I'll have to wait to see how well they hold up.


quote
Originally posted by Will:
Who does the spline work? I have a BMW application that will require some custom splines.



I got more information about this today. I doubt it would be worth your while to send your axles up North, but the local shop that can do the work is called Scotia Machine Service Ltd in Kentville, Nova Scotia (902) 678-1100 (about 15 mins from my place). He estimated it would cost between $60 - $70 per end.


quote
Originally posted by Will:
What's the OD of [the Cobalt axle rod] shaft?



The spline major diameter is 1.075", which is only 12 thousandths larger than the Fiero manual transmission axles. The machine shop believed the difference to be insignificant for the purposes of re-splining the Fiero shaft.


quote
Originally posted by Will:
What's the OD of [the Cobalt tripot stub] shaft?



I didn't check and the tripots are now rather tightly seated in my transmission. Those snap rings really hold on!


quote
Originally posted by Fieroguru:
The F40 and F35 both use 27 spline for the differential to tripod interface, but the design of the actual tripod housings are indeed different.



I stand corrected. I remember now why I wanted to use the Cobalt tripots instead of the larger G6 ones. I wanted to avoid any potential clearance issues between the engine block and the passenger side tripot. I recall this was a problem area in your LS4 thread... to the point that you needed to hammer down the boot clamp nib on your G6 tripot to be certain it wouldn't hit the block. The Northstar has a similar clearance issue when using a jack shaft. You sent me the exterior dimensions of the G6 tripot a while back and I remember thinking that the clearances would be too close for comfort so I went with the smaller (albeit weaker) Cobalt tripots.


quote
Originally posted by Fieroguru:
Where the ability to interchange axles for an F40 hits a road block is normally on the tripod side. If the housing uses larger rollers (F40) and the roller housing has a unique spline count, then it becomes difficult to either find a tripod roller setup that fits the housing, or a longer (or shorter) axle shaft with the same splines for the roller housing.



You hit the nail on the head. There are many different parts that can be cobbled together to make any number of (outer) CV joints and axle rods mate up with the Fiero bearing. The problem is mating one of those axle rods to a tripot spider from the g6 or Cobalt/Equinox. We should start a new thread called "F40 Axle Compatibility in a Fiero" where the different combinations and permutations of parts that will match up to make a single axle assembly are listed in tabular format. The written format is just too complex. Perhaps I'll start such a thread once I get a few more measurements from the Cobalt axles... but at the moment I'm having a hard time removing the Cobalt CV joints off the axle rods. They use a blind snap ring but the shoulders of ring groove were likely cut too sharp or too deep to pull them off. Grrrr...
Bloozberry MAR 18, 02:49 PM

quote
Originally posted by kennn:
...I find it curious that the Cobalt axle has 24 splines.



Where did you read that? I hope it's not one of my typos... I'm trying to be as careful as possible about this info because there are too many threads that have been ruined by this type of confusion. To clarify, the 2005-2008(?) Cobalt SS with supercharged 2.0L engine (not the later turbocharged engine) has a tripot joint stub axle with 27 splines. The bare axle rod that mates with the tripot joint spider and the CV joint spider has 25 splines on a 1.075" diameter shaft. Finally, the CV joint spindle shaft (that mates with the wheel bearing) has 32 splines and is 1.063" in diameter.
fieroguru MAR 18, 05:46 PM

quote
Originally posted by Bloozberry:
but at the moment I'm having a hard time removing the Cobalt CV joints off the axle rods. They use a blind snap ring but the shoulders of ring groove were likely cut too sharp or too deep to pull them off. Grrrr...



Remember our different approaches of removing the decklid hinge boxes? This is another time where crude/brute force can be the quicker/easier method. Take the boot off the shaft, so all that is left is the axle shaft and outer cv. Find a stout surface with a hole or slot large enough to pass the axle through, but not the CV housing. Get some gloves, pass the axle shaft through, grab it with your strong hand, then yank it down as quick and has hard as possible (and watch for flying CV housing). Repeat as necessary.

You could clamp the CV end in a vice (or pass the stub shaft through a hole in the wall) and then use some U-bolts around the shaft to attach a hook that could be used with a slide hammer.

[This message has been edited by fieroguru (edited 03-18-2014).]

Austrian Import MAR 18, 05:54 PM
Do you have a few moments to address what would be different in using a 'pre '88 as a source, as those bodies are far more common to potential builders?

If you haven't addressed this yet, how would this interact with a 'pre '88 front end, which some may want to use to avoid the pitfalls of harder to get '88 wheel bearings (or just because they started with a 'pre '88 body).
Bloozberry MAR 18, 06:22 PM

quote
Originally posted by fieroguru:
This is another time where crude/brute force can be the quicker/easier method.



I already tried that method and a slightly different one with the slide hammer. Then I took the axles to the transmission shop where they tried with a weird combination of bearing pullers and even they couldn't get them apart. I then took them to the machine shop that's going to do the re-splining and left instructions that it didn't matter if either the Cobalt axle groove, snap ring, or the spider broke since I'm not using any of those parts.

[This message has been edited by Bloozberry (edited 03-19-2014).]

Bloozberry MAR 18, 06:25 PM

quote
Originally posted by Austrian Import:
Do you have a few moments to address what would be different in using a 'pre '88 as a source, as those bodies are far more common to potential builders?



Max, would you mind if we took this up in your "redesign" thread? I'd like to try to keep my thread on topic since axles are confusing enough!
Austrian Import MAR 19, 07:09 PM

quote
Originally posted by Bloozberry:
Max, would you mind if we took this up in your "redesign" thread? I'd like to try to keep my thread on topic since axles are confusing enough!


Yes, of course, much better idea.
Bloozberry MAR 21, 09:29 PM
To get back on track, here's how I figured out how much longer my axles rods needed to be:

I started with the Driver's side so first, I picked a convenient reference point on the outer CV joint. I chose the nice line formed where the tapered portion meets the flat portion. Next, I chose another convenient point on the back side of the knuckle; the large flat area next to the bearing hole. Then I made sure the CV joint was fully seated in the knuckle and measured the distance between the two points: 25 mm (red arrow)



Next, I pulled the CV joint out of the bearing and slid the axle assembly towards the transmission until the tripot spider assembly bottomed out into the tripot cup. Then I measured the distance between my two reference points once again. This time I got 107 mm:



Finally, I took the same measurement after pulling the axle back towards the wheel until the tripot rollers were close to the edge of the tripot cup and almost ready to fall out. I got 65 mm this time. Here's a summary of the measurements:



To find out how much longer my new driver's side axle needs to be compared to the Cobalt SS axle, I went through the following simple calculation:

((107 mm - 25 mm) + (65 mm - 25 mm)) / 2 = Additional Length

(82 + 40) / 2 = 61 mm Additional Length

I repeated the same exercise for the passenger side and found that the passenger axle needed to be 140 mm longer than the Cobalt SS axle. I didn't photograph me holding the ruler since I figured it would be overkill, but for interest's sake, here's how deep the tripot joint seats into the jack shaft. You can see why I was a bit concerned that the larger G6 tripots might not have enough clearance to the side of the engine block:



So, the only piece of the puzzle that is missing is the length of the Cobalt axle rods, so that I can add 60 mm to one and 140 mm to the other. Unfortunately I couldn't measure the Cobalt axle rods since I couldn't get the CV joints off them. I know it's a bad idea to give the machine shop too many instructions, but I dropped off the Cobalt axles and the Fiero axles with instructions to remove the CV joints, measure the Cobalt axle lengths, add 60 and 140 mm to that length, then cut and re-spline the correct ends of the Fiero axles to those new lengths. I made sure to give the shop diagrams, simple step-by-step instructions, and my phone number so that I could watch (and take pictures) when they modify them. They're back logged with work right now so it will be about two weeks before they're done.