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Discussion Starter · #21 ·
There is no other support between the mount brackets.
The standard full size tires are 215/75/15, the spare 145/70/16. Here is a comparison:
Tire Wheel Automotive tire Synthetic rubber Tread

(do your own here! Tire Size Comparison )
Mine is in the same boat with original air. One can imagine how much cleaner it is in there. My rim could use a good wire brushing and paint as well. I wonder how rusty inside the tire might be. I carry plugs and compressors, so I only use spares when something happens that can't be plugged.
The hitches I found are designed to go around smaller spares on all models, but only go around the full size spares on extended body. Model specific ones are "no drilling necessary". I'm not certain about multi-fits.
As I have a smaller spare, door mount for me is moot.
They make steps for hitch receivers, in several functions too.
I may have access to a welder, and in theory all it would take is to weld a piece of 2 inch stock between the bumper brackets and then attach the 5k cap hitch to the stock and viola', but the cost/effort/effectiveness vs. say a used hitch for $100, doesn't add up to worth it, so far.
 

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1998 LS AWD Forest Green metallic
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I picked up a 'spare' rust-free heavy duty frame mount hitch from a Pickn\'Pull for $40. I thought it might be useful for modification at some point to do a receiver location flip, so the receiver comes out through the bumper, instead of from underneath (more rear end overhang clearance).
Rod J
Issaquah, WA
 

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Discussion Starter · #23 ·
I picked up a 'spare' rust-free heavy duty frame mount hitch from a Pickn\'Pull for $40. I thought it might be useful for modification at some point to do a receiver location flip, so the receiver comes out through the bumper, instead of from underneath (more rear end overhang clearance).
Rod J
Issaquah, WA
I was thinking of something like that where I could cut out an opening in the face of the bumper for the bumper mounted hitch, but between the bolts still coming out the top and the work involved (not much really) for the return, I decided to just look for a frame hitch. It would look better as it wouldn't necessarily be visible, and would definitely hold / pull the weight.
It's nothing urgent, just as a matter of convenience mostly, so I too, am looking for used.
 

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2004 Astro V6
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Mine IS AWD so therefore the temporary spare has to be the same sizebasic diameter as the 215s....but how long does one really want to run the temporary spare..say if you have a flat on a long trip? That unused spare maybe a bit taller than a used 215.
The local Pick-n-Pull junkyard( a mile from me) does list their "trailer hitch" price on their website at $30.99 "without the ball"..the ball at $5.99(with the 2" extension bar?)..but add the 10% local tax..is where the $40 winds up here in WA..what Rod's price was.. That's a good deal!I don't know if you have Pick-n-Pulls in your area..but the local JYs might give you a similar price for one already off a vehicle.Personally,I'd rather pull my own to make sure it came off an Astro or Safari of similar year,,and you get the correct bolts to go with it!.But I don't need one right now.
My 18" wheeled temporary spare below.. Isn't that a pretty thing?(same diameter as a 215.
Of course since I'm running a smaller set of 205s at the moment..I couldn't use it anyway,one of the reasons I set up a full size spare of the correct size/style for the AWD van.The 205s I have on now came with another Astro steel rim set(basically I ended up with the new rims for close to free..$50 for the caps.. if I had bought the slightly used tires new.)that I am using now,bought for a good "barely used" price..all season radials with good tread.Once they get close to their "end of life",I'll probably switch back to 215s.I'm not seeing too many long hauls this year..mostly just staying within WA state..maybe 200 mile trips max.I need to take at least one of those trips a month during the summer+ months for "house/yard maintenance"...and maybe sneak in some ONP ocean beach hiking while I'm up out there...
Tire Wheel Synthetic rubber Automotive tire Motor vehicle
 

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Discussion Starter · #25 ·
Mine IS AWD so therefore the temporary spare has to be the same sizebasic diameter as the 215s....but how long does one really want to run the temporary spare..say if you have a flat on a long trip? That unused spare maybe a bit taller than a used 215.
The local Pick-n-Pull junkyard( a mile from me) does list their "trailer hitch" price on their website at $30.99 "without the ball"..the ball at $5.99(with the 2" extension bar?)..but add the 10% local tax..is where the $40 winds up here in WA..what Rod's price was.. That's a good deal!I don't know if you have Pick-n-Pulls in your area..but the local JYs might give you a similar price for one already off a vehicle.Personally,I'd rather pull my own to make sure it came off an Astro or Safari of similar year,,and you get the correct bolts to go with it!.But I don't need one right now.
My 18" wheeled temporary spare below.. Isn't that a pretty thing?(same diameter as a 215.
Of course since I'm running a smaller set of 205s at the moment..I couldn't use it anyway,one of the reasons I set up a full size spare of the correct size/style for the AWD van.The 205s I have on now came with another Astro steel rim set(basically I ended up with the new rims for close to free..$50 for the caps.. if I had bought the slightly used tires new.)that I am using now,bought for a good "barely used" price..all season radials with good tread.Once they get close to their "end of life",I'll probably switch back to 215s.I'm not seeing too many long hauls this year..mostly just staying within WA state..maybe 200 mile trips max.I need to take at least one of those trips a month during the summer+ months for "house/yard maintenance"...and maybe sneak in some ONP ocean beach hiking while I'm up out there...
View attachment 285377
Now that rim looks like it came from the front of a farm tractor!:ROFLMAO: It's probably how mine will look if I take it off and clean it.
I try not to use the smaller spares for several reasons. The difference in size and tread pattern makes for differences in stability & control. Then they are only rated for 50mph. You are playing with your life going that slow in these parts.
I look on craigslist. I got my outback's hitch from there. Went to my closest u pull it today. They only had 3 Astros, none with a hitch. I don't think anyone lists them in inventory. I'll just have to use it as an excuse for small road trips when bored.🏍
 

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2004 Astro V6
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You should remove your spare and at least check out the cable/drop assembly and grease it up,make sure the cable is in good shape and not frayed or worn.My cross piece on the bottom of the cable is barely big enough to get across the gap of the center hole and it was hanging funny..but it was still there!
I bolted about a 6" piece of unistrut to make SURE my full sized one stays in place and solid there...
I think if that big ugly ol' spare fell off of there on the freeway it could of totaled out a Prius!:eek:
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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I'll assume it's understood by all that a matching spare is essential with an AWD.
(by the way, any size even oversize will fit underneath with a tow hitch)

I'll admit I've driven my AWD with a mismatched spare.. had no choice at the time.
Blowout on the road.. and just a short drive back home.
Better than nothing.. short term damage should be minimal... but no way to verify that.
With the 233 transfer-case upgrade.. it's no longer an issue.

For long out-of-state trips I now carry two spares... one 30" matching, and one standard size (that I carry underneath). But I can say many years ago I've driven on a "donut spare" for over 100 miles in a previous 2WD Astro at highway speed.. with no issues whatsoever, other than looking silly.

Here's what looking silly looks like with a 27" full sized spare on a lifted van... lol
Good enough till I get home and fix and replace tire
Wheel Tire Automotive parking light Car Vehicle


Not my first time either.. I think I've had all 4 sides eventually go on me.
The last two oddly were sudden failing cracked valves with steady leak-down while driving..
Tire Wheel Automotive parking light Land vehicle Vehicle
 

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Discussion Starter · #29 ·
@Mmusicman

If you look at the pics I finally took, you can see my spare already sticks out under the bumper a bit. The sellers state "may not fit" not "does not fit". If it would fit, I'd like to see it, but again, it isn't really an issue as I have rwd only and a smaller spare.
Good point on all diameters being the same on AWD. It's not something that ever crossed my mind before. I would think with the slip diffs, the worst that could happen is tires being worn out faster as something is going to drag a bit. If you are in slippery weather, you may have a difference in control, (probably in dry too) but nothing is really going to drag with any friction.
Of course it could buck the diff too.😬
 

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I would think with the slip diffs, the worst that could happen is tires being worn out faster as something is going to drag a bit..
No, the "drag issue" is that the AWD transfer case senses the difference between front and rear driveshaft speeds. If it engages, you will have internal damaging results. Minimal differences may cause partial engagement.. but still damage is occurring. In a pinch, the ATC fuse could be pulled to prevent engagement.

The other issue is that the AWD transfer case utilizes "pre-load" on the internal clutches.. and even when not engaged there is STILL pre-load. Any variation between front and rear speeds WILL cause damaging clutch wear and eventually ultimate failure. Most people don't even know they have clutch failure until they find themselves wondering why their front wheels aren't pulling when engaged and needed.

BUT... zero issue with mis-matched sizes on RWD van.
 

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Discussion Starter · #31 ·
No, the "drag issue" is that the AWD transfer case senses the difference between front and rear driveshaft speeds. If it engages, you will have internal damaging results. Minimal differences may cause partial engagement.. but still damage is occurring. In a pinch, the ATC fuse could be pulled to prevent engagement.

The other issue is that the AWD transfer case utilizes "pre-load" on the internal clutches.. and even when not engaged there is STILL pre-load. Any variation between front and rear speeds WILL cause damaging clutch wear and eventually ultimate failure. Most people don't even know they have clutch failure until they find themselves wondering why their front wheels aren't pulling when engaged and needed.

BUT... zero issue with mis-matched sizes on RWD van.
My subi is AWD. It does have a full size diameter spare (not width). This is probably why. I'm going to look into all that more as it never crossed my mind before.
I don't remember what size my s-15 had on it when I caught a slate topped planter with my sidewall in a snow storm....I'm going to look that up just because, if I can find out. It was probably full diameter. At any rate, I still made it to a shop to get the full sized replacement done in 4x4 with it. If it was smaller, I would think it's because it didn't have the traction on dry ground to cause a difference in speed.
I can see a transfer case having an issue with difference in speed, but I imagine that the slip diffs wouldn't let the transfer case feel it. The point being when cornering, one wheel is traveling faster than the other, and most likely all 4 wheels are traveling at different speeds.
If there were 2 different ratios, on the two diffs, or 2 different sized pairs between front and rear, that would definitely wreak havoc.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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I can see a transfer case having an issue with difference in speed, but I imagine that the slip diffs wouldn't let the transfer case feel it.
I don't know where your "imagination" came up with that, but it's wrong.

PS Sidenote: Not all AWD's operate the same. The Astro AWD however, is full-time utilizing pre-loaded clutches (even when not engaged). Most 4x4's do NOT have this issue, since they don't utilize clutch-packs.
 

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Yes cornering will not be perfect.
It's incremental wear that can't be avoided over a long period of time.
But a long-term mismatch of steady full-time highway speed will destroy.
Not sure why we are debating this.

Ironically (in case you didn't know).. the AWD has a common issue of actually locking up in tight turns causing bind. This is part of the reason for the special AutoTrac II fluid, that allows for some slow speed slippage, while still being able to grab when needed. But the pre-loaded clutches are always engaged, and different sized tires (even on one side) will cause drive-shaft speed variations between front and rear.

Now if you had same mismatched tires both front and rear (one front, one rear, each one side only).. the prop-shaft (drive-shaft) speeds would match, and in this hypothetical situation, there would be no damaging wear to the transfer case. And yes, in this case the differential spider-gears would do their thing... but with both front and rear doing the same thing at the same time being equal.

With differentials, when one side spins slower, the other side is spinning faster.. and the net result is the average of the two. Nothing slips here. If front and rear averages (drive-shaft speeds) don't match... you'll have trouble.

Let's talk about bumper hitches... you can be the expert
 

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Discussion Starter · #35 ·
Yes cornering will not be perfect.
It's incremental wear that can't be avoided over a long period of time.
But a long-term mismatch of steady full-time highway speed will destroy.
Not sure why we are debating this.

Ironically (in case you didn't know).. the AWD has a common issue of actually locking up in tight turns causing bind. This is part of the reason for the special AutoTrac II fluid, that allows for some slow speed slippage, while still being able to grab when needed. But the pre-loaded clutches are always engaged, and different sized tires (even on one side) will cause drive-shaft speed variations between front and rear.

Now if you had same mismatched tires both front and rear (one front, one rear, each one side only).. the prop-shaft (drive-shaft) speeds would match, and in this hypothetical situation, there would be no damaging wear to the transfer case. And yes, in this case the differential spider-gears would do their thing... but with both front and rear doing the same thing at the same time being equal.

With differentials, when one side spins slower, the other side is spinning faster.. and the net result is the average of the two. Nothing slips here. If front and rear averages (drive-shaft speeds) don't match... you'll have trouble.

Let's talk about bumper hitches... you can be the expert
I wasn't debating anything. Just let you know where I got the thought about how a transfer case wouldn't be bothered by a smaller spare.
Otherwise, it's all pretty informative. As I said, I never put much thought into how an AWD system works and it's quirks. (yes, done on purpose. I'm cracking myself up here.:LOL:)
I haven't driven a GM AWD, but I have felt binding in 4X4 modes in my S-15 and Sonoma. I haven't felt it in my Outback, but I did do a tight u-turn today faster than I usually did, and I did hear a whole lot of clicking. I just had them axles replaced in the past 2 years and maybe put 20k miles on them. That better be the last I hear that for a while.
As far as the informative discussion goes, yes, I'm sure there are other threads to read all about it, and the information I originally was looking for seems to have been found to the best of anyone's knowledge, and I concluded my original idea of putting a bumper mount receiver wasn't in my best interest, at least not with what's available or modifying my bumper to the point of not being worth the cost in time and money. I guess we can all move along now. Nothing more to see here.😎
Thanks everyone and until next time!
 

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Just a short note..Yes I understand the matching diameter AWD idea,why I added a matching wheel and spare tire(same diameter/size,not brand but close) for the AWD one...When I change the "set" for the other set I have,I'll add another spare of the correct size for the other tires also.The second set has studs..so they will be pulled or another studded one to match..
On my 2004(AWD)..I can add bigger tires on the back only..if I want that look...and keep a somewhat similar single spare to both.
Personally..nothing can outdrive an AWD Astro/Safari in snow..Well,maybe a military tank!😁
Okay..off topic closed here..
 

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I had a similar problem were my tires on my 2002 AWD were smaller than the ugly big 215 spare.
I had a flat out in the country and only had that spare tire with me.
When I placed on the truck and started driving, the drive train would fight with me if I got to speeds over 15 to 20 mph.
Even though I drove half on the payment and the other have on the gravel edge it was still fitting the mismatch.
After 10 miles or so the it stopped doing that and I was able to drive to normal speeds.
I thought for sure I ripped the gears apart in the transfer case when it stopped fitting.
After I got back home and fixed the tire it still drove normally in 2wd. In AWD it wasn't there anymore in the snow.
Only at the end of winter I read that the ATC fuse in the engine fuse block controlled the AWD.
I looked into mine and it was blown. I replaced the fuse and low and behold I got my AWD back.
I didn't have much snow left to try it out properly but the little that was left in driveway told my that the AWD was still working.
How well it will work and how much damage had been done to it? I will find out this coming winter.
 

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Discussion Starter · #38 ·
... A month and three weeks later...
If anyone is still paying attention to this,
I got a proper hitch today. It's a Reese multifit, with a 5k lb tow 500 lb tongue cap (6&6 in W.D., but in theory that's more than I'll ever need).
I would have preferred a direct fit, but seeing how likely that was, and the fact that in the future I can move to another vehicle, if by then needed and I'm around to do it, I went with it. $75 got me the receiver assembly, hitch bar, and 2"ball out of a salvage yard. I still need a pin and some replacement mounting hardware, as what was originally used had been cut for removal. I probably already have half of that since I never returned the hardware I bought when I thought the bumper mounted equipment might work.
 
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