Gripper Limited Slip Technical Thread

[Geoff]

is there any way to adjust the preload? Extra stack from a clutch pack?

[Geoff]

Last night I re-fitted the stock diff into the 4spd I was using to test fit the gripper. The gap between the ring gear bolts and the gear selector shaft is pretty tight.


I stuck some feeler gauges in and measured the gap at 0.070"


The ring gear mounting flange on the Gripper diffs are 0.100" thicker than the stock ones. So on this box there is 0.030" of interference and something would have to be done to make it fit. The backlash on the R&P seemed a little big and I approximated it at about 0.010" more than it should be, so in reality there may only be 0.020" interference. But still there is interference and some distance should be regained, preferably more than the minimum required to fit so that if the backlash is adjusted there is some room to move. Jennifer told me yesterday that the gear shift selector shafts are actually hollow and just have a welded solid plug on the end, so trying to grind that down wouldn't really be an option. I think 0.050" could be taken off of the ring gear flange just under the bolt heads without there being a problem. I'll need to call Tom and talk to him, I may be able to get to that tomorrow. It may be that this isn't a problem on all boxes...

I think the portion of the aluminum case that needs to be removed is maybe around 0.030" of the corner where the gear shift selector shaft goes through and is visible in the pictures above. That won't really be a problem, the interference with the selector shaft is the problem.

[allessence]

One question to ask would be what kind of gear lube should we be using.

Any synthetic is what Tom said.

[allessence]

is there any way to adjust the preload? Extra stack from a clutch pack?

You can move a clutch disk next to another clutch disk for less grip. Changing the stack arrangement will change the amount of grip.

I wish Tom would fab up some quick notes for us newbies.

[allessence]

Hi Jennifer, it is perfectly ok to replace it, and make sure you locate it properly. item 1 for more or less grip, stack the plates in a different order. ie;- more or less friction faces. item 2 preloaded adjusted by thick or thin clutch plates. item 3 preload has been set by me approx 80 ft/lbs and will settle to about 40. DO NOT GET WORKED UP ABOUT PRELOAD. Regards Tom

I don't really have a clue as to what he is saying here.

We only recieved one thickness of clutch plate.

Maybe you guys can understand this.

[allessence]

This is a sheet I made up a few years ago for ordering and assembling 89-94 trans.

TRANSMISSION: Spec’s & setting up.

Input shaft Nut: (large nut) 74 ft lbs +/- 7.4 ft lbs
Output shaft nut / 5th gear nut (small nut) 37 ft lbs +/- 7 ft lbs
All case bolts 20 ft lbs
Trans to engine 22 ft lbs

Differential Bearing pre load setting/ shimming:

Left hand bearing housing (no shims) torque to 17-21Ftlbs
Right hand bearing housing use 3 bolts spaced evenly and equally tighten to 1.6Ftlbs
Measure around with feeler gauge and select shims based on median feeler gauge measurements + .008 in for preload

Rolling resistance value New bearings (1.33 – 2.07 ft lbs) used ( .59-.95 ft lbs)

Crown wheel back lash Used 0.17+/- 0.05MM (0.007” +/- 0.002”)

Input Shaft Bearings: No play/ No load on bearings. Shim to appropriate value. Torque nut to 74ft lbs +/-7.4 ft lbs.

Primary chain case: Ball bearing, Needle bearing
Ball bearing retaining plate (Torx screws) 6-10ft lbs with blue loctite

Pinion Nut preload: Fit nut and using torque wrench on nut 1.8 ftlbs , 15lbs spring scale.

Syncro: (balk rings) 11 teeth between spring ends
(89)
91-94 900 5Speed

7496003 Trans gasket set 1

8726333 Lay shaft 1

8712853 Counter shaft needle bearing 1

8726887 Lay shaft inner bearing 1

8728461 1&4 ,2&3 Syncro 4

8729105 Front Pinion Bearing 1

8729113 Rear Pinion Bearing 1

8700767 Roller Bearing 1

8344772 5th gear syncro 1

8712838 Roller bearing 1

8726168 Crush collar 1

8718371 Pinion End shaft Nut 1

[Geoff]

Hi Jennifer, it is perfectly ok to replace it, and make sure you locate it properly. item 1 for more or less grip, stack the plates in a different order. ie;- more or less friction faces. item 2 preloaded adjusted by thick or thin clutch plates. item 3 preload has been set by me approx 80 ft/lbs and will settle to about 40. DO NOT GET WORKED UP ABOUT PRELOAD. Regards Tom

I don't really have a clue as to what he is saying here.

We only recieved one thickness of clutch plate.

Maybe you guys can understand this.

I think I can help interpret, plus I talked to Tom earlier about some similar stuff.
What he is saying is you can adjust the grip by changing the order of your clutch packs. I think they are set up at maximum grip right now (inside splined then outside splined then inside splined) as shown in this photo

I'm not sure if we could put another inside splined clutch plate between the two outside splined plates at the top of that stack. There might not be enough room in the diff, plus it would also give the diff more pre-load. The pre-load is adjusted simply by having more stuff crushing against the clutch plates. This can be accomplished by putting in thicker clutch plates (which we don't have any with different thicknesses to chose from, maybe Tom makes some?), or by replacing the large Belleville washer at the ends of the clutch plate stacks with a thicker (or thinner if you want to lower pre-load) one. The Belleville washer is the dark one just inside the diff housing on top of the clutch plate stack in this picture


Tom told me that the method of using the Belleville washer and thus having an adjustable pre-load was first implemented by companies like ZF when they were first designing these diffs. It was their solution to getting some pre-load due to manufacturing tolerances.

We have a lot of clutch plates in this diff so I think it should work well. I am going to look into the diff and take some measurements of the Belleville washer to see if there are any standard ones we can buy with differing thicknesses if anyone wants to adjust their pre-load. Tom didn't seem to say that pre-load was something to be too concerned with, but he also said that I'd change it if I were to thin the inside of the ring gear flange on the main case and that all of the dimensions would get messed up (which I knew but I was trying to figure out what would happen if I made a new top cap for the case and modified the case to thin out the ring gear mounting flange).

I also talked to him about the fit issue I was having with the bolts interfering with the gear selector shaft. I asked him if I could take some material off the face of the ring gear mounting flange on the top cap of the diff on the surface just under the bolt heads (the surface the blue arrow on the right points to)

I told him I would want to try to take 0.040" to 0.050" off since I have around 0.030" of interference. He said I could do that but to take off as little as possible. He suggested taking some off the bolt heads too but then took a look at them and figured that the bolt heads weren't all that tall to begin with and it wouldn't be wise. He suggested taking some off the gear selector rod too but I told him that I have been informed that they are hollow so he said the face of the diff top cap would be best. I'm not planning on using the diff in this 4spd so it may be possible that there won't be interference in a different box but I doubt manufacturing tolerances in these boxes would be off by 0.030"

Tom said a few people in the UK have installed theirs already and haven't reported any problems with fitting at the gear selector shaft. Maybe Sonett will chime in?

[allessence]

Hi Geoff,

Thanks for the translation.

While you still have your unit apart would you mind measuring the wavey end spring. I'm going to buy some new ones.

I looked at McMaster but didn't have any measurements to go by.

Thanks

[allessence]

Does anyone have a bearing house they use for Trans bearings on a regular basis?

I've been buying all mine from SAAB but they are a little pricey. Also, has anyone tried to fit a tighter tolerance 5th gear cover/ pinion end bearing?

The current one has a rating of 3 and is pretty loose. The ratings are 1 tightest, 2 looser, and 3 the loosest. I have the bearing number here somewhere.

[Geoff]

I measured the Belleville washer last night but forgot the measurements at home so I'll have to look it up later. I'll measure the wave spring this weekend and I'll bring it to work with me on Monday and put it in the UTM and measure the load and deflection so we can properly source the right ones.

I've used Eastern Bearing in Fitchburg, MA for a bearing once (B engine water pump bearing, standard R-10 bearing...) http://www.ebearings.com
I also saw this place when I was looking for the Eastern contact info http://www.futurebearings.com/main.htm

[sonett]

Does anyone have a bearing house they use for Trans bearings on a regular basis?

I've been buying all mine from SAAB but they are a little pricey. Also, has anyone tried to fit a tighter tolerance 5th gear cover/ pinion end bearing?

The current one has a rating of 3 and is pretty loose. The ratings are 1 tightest, 2 looser, and 3 the loosest. I have the bearing number here somewhere.

I never buy my bearings from Saab, you can get the same bearings much cheaper from a bearing stockist.

Jen, be carefull fitting a tighter spec bearing, i think the bearing you are describing is a C3, it is at this tolerance for a good reason (13-28 microns), when cold it will feel loose, but when it has warmed up the tolerance will reduce, the standard spec in this bearing will be CN (5-20 microns) If anything you may need to go to C4(23-41 microns) but i don't think it's needed with this box, the V4/stroker boxes however benefit from certain C4 bearings.
I only use Timken when using a taper roller bearing, such as the front pinion bearings or the inner drive shaft, these are the best you can buy, i use SKF for the roller bearings or RHP, SNR, i never use Jap/Chinese bearings.

[sonett]

I've used Eastern Bearing in Fitchburg, MA for a bearing once (B engine water pump bearing, standard R-10 bearing...) http://www.ebearings.com
I also saw this place when I was looking for the Eastern contact info http://www.futurebearings.com/main.htm

The B series water pump bearing is a bit of an oddball because it's an imperial size and is therefore usually quite expensive compared to similar sized bearings, i am just rebuilding a 99T engine and box for someone, the engine was running fine when removed, when i removed the water pump over half of the bearings and part of the race were missing, but the pump was some how still working, the bearing was a jap bearing, only use SKF for this bearing, every journal on the crankshaft is scored, some quite deeply.

[sonett]

Hi Jennifer, it is perfectly ok to replace it, and make sure you locate it properly. item 1 for more or less grip, stack the plates in a different order. ie;- more or less friction faces. item 2 preloaded adjusted by thick or thin clutch plates. item 3 preload has been set by me approx 80 ft/lbs and will settle to about 40. DO NOT GET WORKED UP ABOUT PRELOAD. Regards Tom

I don't really have a clue as to what he is saying here.

We only recieved one thickness of clutch plate.

Maybe you guys can understand this.

I think I can help interpret, plus I talked to Tom earlier about some similar stuff.
What he is saying is you can adjust the grip by changing the order of your clutch packs. I think they are set up at maximum grip right now (inside splined then outside splined then inside splined) as shown in this photo

I'm not sure if we could put another inside splined clutch plate between the two outside splined plates at the top of that stack. There might not be enough room in the diff, plus it would also give the diff more pre-load. The pre-load is adjusted simply by having more stuff crushing against the clutch plates. This can be accomplished by putting in thicker clutch plates (which we don't have any with different thicknesses to chose from, maybe Tom makes some?), or by replacing the large Belleville washer at the ends of the clutch plate stacks with a thicker (or thinner if you want to lower pre-load) one. The Belleville washer is the dark one just inside the diff housing on top of the clutch plate stack in this picture


Tom told me that the method of using the Belleville washer and thus having an adjustable pre-load was first implemented by companies like ZF when they were first designing these diffs. It was their solution to getting some pre-load due to manufacturing tolerances.

We have a lot of clutch plates in this diff so I think it should work well. I am going to look into the diff and take some measurements of the Belleville washer to see if there are any standard ones we can buy with differing thicknesses if anyone wants to adjust their pre-load. Tom didn't seem to say that pre-load was something to be too concerned with, but he also said that I'd change it if I were to thin the inside of the ring gear flange on the main case and that all of the dimensions would get messed up (which I knew but I was trying to figure out what would happen if I made a new top cap for the case and modified the case to thin out the ring gear mounting flange).

I also talked to him about the fit issue I was having with the bolts interfering with the gear selector shaft. I asked him if I could take some material off the face of the ring gear mounting flange on the top cap of the diff on the surface just under the bolt heads (the surface the blue arrow on the right points to)

I told him I would want to try to take 0.040" to 0.050" off since I have around 0.030" of interference. He said I could do that but to take off as little as possible. He suggested taking some off the bolt heads too but then took a look at them and figured that the bolt heads weren't all that tall to begin with and it wouldn't be wise. He suggested taking some off the gear selector rod too but I told him that I have been informed that they are hollow so he said the face of the diff top cap would be best. I'm not planning on using the diff in this 4spd so it may be possible that there won't be interference in a different box but I doubt manufacturing tolerances in these boxes would be off by 0.030"

Tom said a few people in the UK have installed theirs already and haven't reported any problems with fitting at the gear selector shaft. Maybe Sonett will chime in?

Geoff, found some time today to trial fit the gripper diff, i only fitted a few ring gear bolts so i could rotate the diff to see if there was a clearance problem with the selector shaft, there is a clearance problem. I fitted the inner drivers with bearings etc and the bolts catch on the selector shaft. The Saab flange is 11mm wide, the gripper flange is 13mm. From what i can see there are three solutions, different bolts, make the flange as per original, grind some material from the selector shaft, the selector shaft is not hollow, at least not on a five speed, i have just cut one up! I am not cutting up my selector shaft, it's a special shaft from Jorgen.
I will call Tom on Monday asking for him to machine the flange.

[Geoff]

Any idea on how much interference you have? I've got about 0.75mm of interference. I don't know what Tom would think about taking a full 2mm off of the flange by removing it from the top plate, it would leave the plate pretty thin. I think removing 1mm should be sufficient. Tom said that should be OK but to take off as little as possible.

I did suggest to him that some of the extra 2mm thickness should be taken from the main diff case on the inside of the ring gear flange (the side that contacts the top cap). That would of course throw all the dimensions off necessitating a new top cap be built.

Interesting to know about the selector shaft. I always thought they were solid too. Jennifer, are you sure they're hollow?

[Luke]

So uh where does that leave those who got these things but don't have access to a lathe. I still don't understand why he split the case there when every other saab diff splits at the other end and can be installed just fine, and we sent him CAD drawings and stuff with dimensions and pictures. I don't personally care because I know I can fix the thing and get it to work for free but if I couldnt and I just dropped $1000 on it i'd be a little peeved.