Don't like my tall 1st Gear - Do my larger tires make the difference?

[Yamariv]

Hey Guys, I've mentioned before on another post that I don't like how tall my 1st gear is in my truck. It seems like I have to slip it forever before getting going.

The truck came with 265/70R15 winter tires on it which even by looks appear much bigger than stock. I did the tire comparison chart with stock (225/70R15) and it says the circumference difference is 88.3 vs 93.0 inches = +4.6% difference.

In your opinions, do you think if I went back to stock with summer tires that the 4.6% difference would make a big difference on how my first gear feels or would this be negligible?

[72SB]

your larger winter tire diameter would have more an impact if your rear gears were high like 2.xx. vs. 3.42 and lower (3.73) rear gear not much of a difference

what rear gear do you have?

[Yamariv]

Originally Posted by 72SB

your larger winter tire diameter would have more an impact if your rear gears were high like 2.xx. vs. 3.42 and lower (3.73) rear gear not much of a difference

what rear gear do you have?

I'm not sure what my rear end is, I was assuming 3.73 but the way 1st gear is tall it can't be.

I plan on changing the rear end fluid and gasket soon so I'll have to check when I'm in there. It will be stamped on the gear correct?

[LockDoc]

Originally Posted by Yamariv

Hey Guys, I've mentioned before on another post that I don't like how tall my 1st gear is in my truck. It seems like I have to slip it forever before getting going.

The truck came with 265/70R15 winter tires on it which even by looks appear much bigger than stock. I did the tire comparison chart with stock (225/70R15) and it says the circumference difference is 88.3 vs 93.0 inches = +4.6% difference.

In your opinions, do you think if I went back to stock with summer tires that the 4.6% difference would make a big difference on how my first gear feels or would this be negligible?

I deleted your duplicate post in the "Projects and Builds" forum. This would be the correct forum for your question....

LockDoc, Moderator
.

[HO455]

Originally Posted by Yamariv

I'm not sure what my rear end is, I was assuming 3.73 but the way 1st gear is tall it can't be.

I plan on changing the rear end fluid and gasket soon so I'll have to check when I'm in there. It will be stamped on the gear correct?

Yes. Like below.

[jimijam00]

I'll just leave this here...

https://www.youtube.com/watch?v=uU6WJXjZf4Y

[Yamariv]

Originally Posted by LockDoc

I deleted your duplicate post in the "Projects and Builds" forum. This would be the correct forum for your question....

LockDoc, Moderator
.

Thanks, I wondered where my first post went.. Must have hit the wrong sub forum, sorry

[Yamariv]

[quote=jimijam00;9163432]I'll just leave this here...

https://www.youtube.com/watch?v=uU6WJXjZf4Y[/quote

Sweet, that's supper easy to calculate that way! Thanks for the video link

[Yamariv]

Originally Posted by HO455

Yes. Like below.

So how do those #'s decipher into the gearing code?

[Steeveedee]

Pinion 13 teeth, ring 40 teeth, 40/13 ~ 3.077, usually called 3.08.

[72SB]

OP

My ring gear had the ratio # stamped on it 11:41 (3:73). divide the larger # (ring gear) by smaller # pinon gear)...original gear.

The spin tire one revolution and count the turns of DS is easy

post 5 ring gear is 13x40=3:08

[Yamariv]

Originally Posted by Steeveedee

Pinion 13 teeth, ring 40 teeth, 40/13 ~ 3.077, usually called 3.08.

Ahh, makes perfect sense!

[Yamariv]

Originally Posted by 72SB

OP

My ring gear had the ratio # stamped on it 11:41 (3:73). divide the larger # (ring gear) by smaller # pinon gear)...original gear.

The spin tire one revolution and count the turns of DS is easy

post 5 ring gear is 13x40=3:08

Perfect! I'll check it in the next few days and report back!

Thanks for everyones help with this!

[Steeveedee]

Make sure to get the right lube when you do this. Some lubes are not appropriate for the old gears like we run.

[Yamariv]

Originally Posted by Steeveedee

Make sure to get the right lube when you do this. Some lubes are not appropriate for the old gears like we run.

Uh oh, what's the wrong lube? I've already bought some Royal Purple full synthetic for it :S

I had read that some of the old standard transmissions don't like full synthetic because of the sycros so I went dino oil for that but had no idea there were wrong oils for the rear diff

[Steeveedee]

You'll just have to look at the labels and the requirements. Hopefully someone will chime in with the proper info. I just know that the wrong lube can trash things.

[Yamariv]

Originally Posted by Steeveedee

You'll just have to look at the labels and the requirements. Hopefully someone will chime in with the proper info. I just know that the wrong lube can trash things.

Are you sure, maybe you're referring to putting in limited slip lube into an non limited slip diff? I'm not sure why any good gear oil could wreck these diffs

[RichardJ]

My understanding and what I have read and use.

These older manual transmissions should have GL-4 oil. The GL-5 is bad for the brass synchro rings. GL-4, synthetic or not will work. If the container says GL-4 & GL-5, don't use it in the transmission. If the container says GL-5 anywhere on the label, don't use it in the transmission.

If the rear end has an open differential, you can use limited slip lube or not, synthetic or not. If the diff is limited slip, then the oil should say that or there are limited slip additives.

[72SB]

OP, if you have a clutch pack type limited slip differential, you do not want to use synthetic gear oil. You use standard gear oil and GM "friction modifier" additive 4 oz bottle

I don't think synthetic otherwise will hurt a rear gear otherwise, but I always use just conventional gear oil

[Yamariv]

That makes sense! It's just a regular 12 bolt rear end (no limited slip) so I can't see a regular or full synthetic oil hurting anything.

Thanks guys!

[Steeveedee]

OK, it must have been transmissions that one had to be careful with. Just trying to help.

[Richard]

A comment on a fairly recent experience. My new front custom fabricated D60 for my K10 had a tag on it that said not to use synthetic fluid. Open diff as I did not want to spring for a locker at this time. From what I understand synthetic is not recommended for the ARB air locker or from Yukon the gears I am putting the rear as well.

Assuming your gears are 3.73. By my calculations your suggested tire size change would be the approximately same as switching to 4.10 gears. Raise rpm about 90.

[mrein3]

Originally Posted by Yamariv

Hey Guys, I've mentioned before on another post that I don't like how tall my 1st gear is in my truck. It seems like I have to slip it forever before getting going.

The truck came with 265/70R15 winter tires on it which even by looks appear much bigger than stock. I did the tire comparison chart with stock (225/70R15) and it says the circumference difference is 88.3 vs 93.0 inches = +4.6% difference.

In your opinions, do you think if I went back to stock with summer tires that the 4.6% difference would make a big difference on how my first gear feels or would this be negligible?

Have you tried starting out in 2nd gear? Back in the day when you had a super low 1st, and you weren't pulling a house off its foundation, you just started in 2nd.

[Yamariv]

Originally Posted by mrein3

Have you tried starting out in 2nd gear? Back in the day when you had a super low 1st, and you weren't pulling a house off its foundation, you just started in 2nd.

My first gear is the other way around, maybe tall is the wrong word but it takes in my opinion way more clutch slippage to get it going and I'm doing 5-6 mph before I can let the clutch fully out. It's not a granny gear at all, the other way around which is pretty annoying for me

[Yamariv]

Originally Posted by Richard

A comment on a fairly recent experience. My new front custom fabricated D60 for my K10 had a tag on it that said not to use synthetic fluid. Open diff as I did not want to spring for a locker at this time. From what I understand synthetic is not recommended for the ARB air locker or from Yukon the gears I am putting the rear as well.

Assuming your gears are 3.73. By my calculations your suggested tire size change would be the approximately same as switching to 4.10 gears. Raise rpm about 90.

I'm probably wrong but wouldn't it be the other way around? More closer to 3.20 something gears?