The Ultimate Syncro Big Tire/Gearing-is going big worth it?

[crazyvwvanman]

I have 215/65R16 in the spare well of a couple of my 2wd vans. For Syncros I would like to use 215/70R16 but only if I can make the spare fit where it belongs. I have been carrying 215/75R15 in there in my Syncros for 20 years and it is a very tight squeeze. I don't mind a little cutting and welding in non-vital locations if that will get 215/70R16 in there.

Mark

[Waldi]

[MarkWard]

The pinion crown would have more teeth sharing the load with a higher number. In other words, more teeth meshed at one time as it turns the ring gear. I get what you are saying though.
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[clift_d]

[crazyvwvanman]

That info shows the tire to be slightly larger in all dimensions, not just diameter. As I said the 215/75R15 is a very tight squeeze so larger in all dimensions isn't going to fit the same in the front spare well. In any case I see that BFG is going to be making the new T/A KO2 in a strong 215/65R16 size soon so that should solve my spare well issues.

http://www.tirerack.com/tires/tires.jsp?tireMake=B...p;i1_Qty=5

Mark

[Jon_slider]

[Syncroweekender]

I have a Bridgestone Dueler A/T Revo 225/70R15 in my clamshell. According to the specs I found it is a bit smaller in diameter than the 215/75R15 BFG (27.4” vs 27.8”) but it is wider (9.1” vs 8.4”). I cut the clamshell pivot brackets off the top of the cross-member and had them welded on the bottom side. Then I pounded down the top of the box section (in front of the big tube) that the brackets are welded to in order to make room for the tire, cut the back edge of the clamshell off so it would pivot and ground a bit off the lower flange of the frame rails. I also had to use a spacer and a longer bolt in the front to close the clamshell. My tire fits pretty close to the frame and the steering shaft. It takes some trial and error to get the tire in the right spot. I strap the tire to the clamshell once it is in the right place so it doesn’t move on me and hit the steering shaft.

I could do a bit bigger diameter tire but I think it would probably have to be skinnier than my tire. I could take more off the lower flange of the frame rails but I think the back edge of a bigger tire would sit higher on the cross-member which reduces the clearance to the steering shaft.

Here a couple of pictures. Note that the clamshell pivot brackets sit lower than the cross-member.

[tjet]

[Steve Arndt]

[tjet]

Yeah there's that. I'm gonna try to recoup some costs by selling my matching 4.86 cores.

[dkoesyncro]

I'd like to add "crawling" to this subject!

Im currently going through the syncro, we've got the gears figured out. The R/P are the next, I've been trying to locate 6.17. I've spanned far and wide. Weddle is an option but....this large investment of running gear and personal opinions of the respected say that the metallurgy of the Weddle is just not the same as the OEM. I have located a good used set in the UK but they are tentatively spoken for.

The respected is now looking to see if he has any 5.83, I have not scoured the Earth for these but, most of those I've spoke with far and wide also say this is difficult to find in good condition too! Yes, Weddle has this ratio but large investment...let's not leave things to chance.

The next thought, if a 4.86 and 5.43 are readily available with reputable quality, do these ratios produce the same amount of swarf backed to a diesel to provide the crawl-ability?

[Steve Arndt]

There is more sliding vs rolling contact with the lower ratio r/p (higher number). So it is weaker because of smaller gear teeth, and has more wear due to the contact.
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Steve
Steve's 87 Syncro project

[Sodo]

[tjet]

Wouldn't a lower R&P gearset (higher numerically) not be as stressed as a taller stock gear?

Also, I didn't think the ring and pinion was the main failure issue with these transmissions.

I'm wondering if a cryo treatment would help these gears...

[Sodo]

[Steve Arndt]

My experience is with T1 and 091 boxes mainly. The rule of thumb (ish) is smaller number lower ratio is stronger.

It depends on the tooth cut profile as well.
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Steve
Steve's 87 Syncro project

[tjet]

I've also read about a process that bakes and the part before the Cryo treatment. They do this before final machining.

[Steve Arndt]

[esmukarlis]

Didn't want to make a new topic and this seemed as good one to put my question.
I am building Syncro for overlanding around North and South Americas and currently going through trans rebuild.

I plan to go with 1z TDI engine (around 90hp), 215/75/R15 tyres (27,7"). I have gearbox with 4,83 R&P ratio. My question form personal experience of some of you - should I go with 0.7 or 0.74 4th gear. I know its not a big difference, but maybe someone used one of them and now are 100% sure, that other one would be best fit for them!

[FrankenSubySyncro]