4wd front diff

M

motorhead

New member
Yea,new syclone owner here so Im ready for the abuse. I found some info on converting the front diff to selectable four wheel drive.seems pretty simple.change the right tube and a few misc parts,I was just going to use a factory servo and put a vacuum solenoid inline with a nice little switch in the cab. An indicator lite would be easy to do just so there is conformation that this thing is either in our out before I romp on it.
My question is has anyone done it? with the awd t-case always being in does it leave to much tension on the front shaft for the servo to slide the gear in the diff? or do you have to put the truck in neutral or back up a bit relieve the tension?
And how much abuse can the awd viscous clutch with stand in 2wd mode?
Forgive me if this topic has been covered but my eyes feel like they are gonna bleed from searching.
 
B

big gear head

axle builder
Re: 4wd front diff

It's been done. When you disconnect the right axle with the cable the front shaft still turns, but the differential spins inside so the wheels don't pull. This is good for doing burnouts with the rear wheels. I built a front and rear differential for some guys in Poland with a Typhoon and that is how I set it up. They like it very well. You can also get one if the manual cable kits that works like a choke cable. I wouldn't try to engage it at more than a slow roll.
 
InvisiBill

InvisiBill

Active member
Re: 4wd front diff

Use http://store.summitracing.com/default.asp?target=partdetail.asp&part=POS-500&autoview=sku rather than trying to copy the crappy vacuum system.

As you'll see in any previous thread about using a 4x4 diff instead, the only real advantage is for burnouts. The transfer case will still be turning the propshaft, so you won't gain any efficiency (unless you also go to a switchable transfer case, and then it's only the propshaft that's not being spun). This will also put more stress on the viscous coupler, though there aren't really any hard numbers on exactly how bad RWD is for it. The stock 4x4 system won't engage or disengage under load - you may be able to switch it while going down the road, but I frequently had to put my S-10 in reverse to get the front diff to actually switch, so don't count on it engaging or disengaging as soon as you flip the switch.
 
M

motorhead

New member
Re: 4wd front diff

Yea,I wasnt after efficiency. Just for burn-out and play in a controlled enviorment. I think that visous clutch would cook after a few miles in 2wd mode.Im going to get with the parts dept.today and order up all the ingredients. Probably use a light duty switch which will control a vac. solenoid for the stock servo thats usually mounted under the batt on a 4wd.maybe I willl put an led on the A pillar by the boost gauge for axle confirmation status.I will post up how it all works out and give a write up on how to and parts needed.give me bout a week
 
M

motorhead

New member
Re: 4wd front diff

big gear head said:
Do you think the vacuum system will work on a turbo truck? Do they have a vacuum pump on them?
Click to expand...
Wow,good point. I guess I may be stuck with the old cable set up. There must be a vac reservour somewhere though cause when Im boosting I never have a problem with my hvac swithing and start dumping out of defrost??? all the hvac actuators seem to hang on for the ride,I need to research this better.
 
QUICK STORM

QUICK STORM

B.A.M.F. BMW Tech
Re: 4wd front diff

motorhead said:
Wow,good point. I guess I may be stuck with the old cable set up. There must be a vac reservour somewhere though cause when Im boosting I never have a problem with my hvac swithing and start dumping out of defrost??? all the hvac actuators seem to hang on for the ride,I need to research this better.
Click to expand...

vacuum resivior is under the battery
 
InvisiBill

InvisiBill

Active member
Re: 4wd front diff

Yeah, right where the vacuum actuator is normally mounted on a regular 4x4 S-10.

Having replaced the actuator and the transfer case switch, my advice is to avoid the vacuum system on a regular S-10, even moreso on a truck that doesn't have any 4WD vac system to begin with.
 
M

motorhead

New member
Re: 4wd front diff

The majority of the time the engine produces enough vacuum so If a check valve is used inline before the solenoid it should hold back any pressure above 0psi from back feeding into the servo. The solenoid has to be equipt with a vent so when its off (2wd selected) the vac will bleed off and let the vacuum out of the servo,or atmosperic psi in for that matter.Will this work???
Oh and parts needed to convert the AWD axle to selectable are like $350 my cost (gm employee) screw that,Im gonna just dig up a bone yard diff and canabolize it.
 
B

big gear head

axle builder
Re: 4wd front diff

You should be able to get one from the junk yard for around $100. They are not much fun to pull out when the engine is still installed.
 
M

motorhead

New member
Re: 4wd front diff

big gear head said:
You should be able to get one from the junk yard for around $100. They are not much fun to pull out when the engine is still installed.
Click to expand...
I was at the bone yard today,$150.00 for the diff. The junk yard dog is going to pull it for me so I dont have to crawl around in the mud. Ive done quite a few T-truck diffs and they arent fun. Im just gonna change out the right tube and the parts inside that make it selectable. I saw the posi loc cable kit,seems pricey for what it is??? $126.00 Found one on ebay for $109.
I think Im going to scrap the vacuum idea.Im thinking it will suck because everytime I shut the truck off the servo will creep back to 2wd and when I start it I will have to wait for it to engage.
Do these cables hook right up to the diff or do they link up to the servo end on the factory cable?
 
Last edited:
InvisiBill

InvisiBill

Active member
Re: 4wd front diff

motorhead said:
I saw the posi loc cable kit,seems pricey for what it is??? $126.00 Found one on ebay for $109.
I think Im going to scrap the vacuum idea.Im thinking it will suck because everytime I shut the truck off the servo will creep back to 2wd and when I start it I will have to wait for it to engage.
Do these cables hook right up to the diff or do they link up to the servo end on the factory cable?
Click to expand...

I haven't actually installed one, but the picture they show doesn't look like it mates up with the stock cable that hooks to the actuator. Then again, there's a little pin that looks sort of like the clip on the stock actuator, so maybe all those little parts are used to connect it to the stock cable (which would probably be easier to hook up, rather than having to get into the diff to hook this up inside). Maybe give Summit a call and see if they can tell you?
 
You must log in or register to reply here.
Top