Dana35 vs Dana35-IFS & DIY LS

[mitchx3]

I have a 1998 sport (4x4, manual, ohv) and want a front diff that's other-than-open.

Was waiting for Torsen to make another run (Torsen® Traction) but they've pushed the date out now from summer 2023, to fall 2023, and finally to "maybe in 2025".

I had seen suggestions that normal Dana35's would fit in the Dana35IFS case but also saw some indications it wouldn't work (some mentioning axle-retention mechanism (c-clip vs circlip)). I decided to give it a shot since I couldn't find good documentation either way. I was hoping the case would be right and I could modify the axle stuff to work.

So I bought:
A front diff/carrier from a 2002 ranger (4.10 gears)
A set of CV axles
A Dana Model 35 - M35 Trac-Lok Posi Unit (M35TL-27-354UP or 74210X)
A case spreader (the common case spreader listed as for Dana30-80 has really big nubs that don't fit the Dana35IFS case (small nubs), but it's probably possible to drill/tap for a 2nd set of smaller nubs )


Dana35IFS on the left, Dana35 on the right:

As you can see, the Dana35IFS is about 3/4" smaller from bearing to bearing.

 

[mitchx3]

Here is the empty Dana35IFS case, you can see the bearing locations:

And here is the non-IFS Dana35 sitting in the Dana35IFS case (you can see its width would put the bearings into the gasket area of the case):

 

[mitchx3]

Here are some dimensions, in case you're like me and want to explore options:

(Ring Gear mounts at C and D and N is the crosspin holding the spiders gears in, if that helps you orient)

I measured in inches or MM depending on what was convenient. Numbers are likely imperfect (my measurement setups were imperfect) but should give a decent idea(within 1mm I think):

Location: A-G	Dana35IFS: 6.625"	Dana35: 7.25"
(A-B) = (F-G)	21.3mm	same as IFS
K=L	41.3mm	same as IFS
B-C	9mm	same as IFS
D	120mm	same as IFS
A-E	85mm	100mm
M	111mm	110mm
N	18mm	same as IFS

Drill pattern for the ring gear is 8 holes, 146mm center-to-center across opposite holes. Hole diameter about 3/8. The ring gear appears to fit both diffs.

 

[Josh P]

Detroit Truetrac 912A569 fits and works. It will work in reverse rotation with less bias. If you need more bias you can open the unit and rotate the internal assembly.

 

[mitchx3]

And some measurements of the output gears/splined areas (the spine count/size seemed to match (27)):
H and I represent locations on the non-ring-gear-side output gear.
H' and I' represent locations on the ring-gear-side output gear.

Location: I-J (this is where the c-clip would sit)	Dana35IFS: ~4mm	Dana35: same
G-H (how far in from the outside edge of the bearing the splines start)	37mm	same as IFS
G-I (how far in from the outside edge of the bearing the splines end)	66mm	same as IFS
A-H' (how far in from the outside edge of the bearing the splines start)	37mm	54mm
A-I' (how far in from the outside edge of the bearing the splines end)	67mm	78mm

 

[mitchx3]

So that said:

If anyone wants to sell me a Torsen for a normalish price, that'd be cool.
If anyone has a known-to-work (first hand info, please!) front LSD model, please post up!

I have ordered some carbon fiber sheet (.5mm and 1mm) and am going to replace steel washer between each output gear and the case (of the factory open diff) with a CF washer and see if I get a ghetto LSD out of it. In theory, I should get about 1/6th the locking power of normal clutch based LSD (1 sliding surface vs 6 per side, where both are about the same area). This based on CF having a higher coefficient of friction than steel and being used in some LSDs. Ideas on how to measure the effect (with the diff out of the car) would be helpful.

 

[mitchx3]

Detroit Truetrac 912A569 fits and works. It will work in reverse rotation with less bias. If you need more bias you can open the unit and rotate the internal assembly.

Are you certain that's the case for 2nd gen explorers? That part as listed for Jeep Rears which is what the too-big diff I have is listed to fit. And typically when people talk about reverse-rotation stuff they're talking about 1st gen explorers with TTB suspension.

 

[Josh P]

Are you certain that's the case for 2nd gen explorers? Is that part as listed for Jeep Rears which is what the too-big diff I have is listed to fit. And typically when people talk about reverse-rotation stuff they're talking about 1st gen explorers with TTB suspension.

My bad, I was thinking the ranger and explorer were the same but 97 down is the same as a 1st gen explorer. Retaining the axle shafts with the IFS Dana 35 seems to be an issue and that case is too big.

 

[mitchx3]

I just ordered this: Quaife Ford Explorer 4WD front ATB Differential
I called quaife directly and they didn't know what model years of explorers that fits. But I've seen a Jeremy Clarkson review of a 2nd gen and the technical drawing (https://shop.quaife.co.uk/wp-content/uploads/2014/03/QDF37Z.pdf) has a date a of 2005 and seems to line up perfectly with the original diff, so I ordered one (~$700 shipped).

 

[mitchx3]

Ok, I have the Quaife QDF37Z. Measurements against the original diff match, it sits in the case about right, the ring gear mounted up correctly.

I did have one annoyance: the clearance around the ring-gear-bolt-holes was small and I had to find a thin socket to tighten them.

I'm using 4.1 gears - I don't know if the Dana35SLA has any carrier breaks. If it does, I would expect 4.1 to be on the high side of that break, and a spacer might make lower ratios work with this diff. Most people adding traction aids probably have/want the higher ratios anyway.

I'll post again when I have the gears setup(gotta pound on some bearings first) and maybe after I've tried it in the truck.
There is less mystery in 'does it work' than 'does it fit'.

Also considering printing mounting bushings for the axle-case out of TPU (95a). In theory I should be able to drop the case like 3/8" in the process.

 

[410Fortune]

I Love this! Nice work

 

[mitchx3]

Initial test drive worked. Mostly just wrapping up/confirming this diff fits. I'll post back if it explodes or something. When I received it, it had dried out oil on it so maybe it had been sitting on a shelf for a while, suggesting buy one now if you want one.