researching diff ratios

[SgtRauksauff]

Greetings!

First, the background:

This isn't particularly Chevy related, but there seems to be much more traffic here than in the Buick section, and chevy parts are more common to find anyway.

I've got an 88 Electra Estate wagon, with the Olds 307, 4bbl, and I believe a 700R4. Well, actually it's my uncle's, but it's not going to be used on the road anymore. Before it gets parted and junked out, I've been rallycrossing it. Pictures Here.

We know the 307 isn't really the torquiest engine around, and it would be easy enough to swap engines, but since it's going to the junk heap soon, that's just too much work.

I've got some awesome tires on the back for rallycrossing with, ~30-year-old bias plies, with 9.50/16.5 Hawkinson treads recapped on. The thing is, these suckers are somewhere around 34+ inches tall, and the torqueless engine combined with the really low diff ratio makes for a VERY long time getting up to speed.

So, I'd like to just find either a good Ring and Pinion, or a whole carrier, or even a whole axle and just slap it in and go, from another car at a junkyard or one of the ones sitting around at various friends and families.

I'm not 100% sure, but I think it's the 8.5" 10-bolt, with like a 2.41 or 2.56 or the like.

So basically, what I'm asking for, is what other vehicles would I be able to find a better ratio in?

So far, on the list to look at are some other b-bodies, oldsmobile delta 88's and 98s, a half-ton pickup/suburban or three. From what I understand, the Astro has the correct bolt pattern and width, but was only a 7.5" ring, so I'd have to yank the entire axle, and re-weld the brackets, and probably mess with the driveshaft.

If it comes down to it, I'll just drive it as is, since it's still a load of fun. But, i think with some shorter gears, and a welded diff, this thing will be a MUCH more fun beast in the dirt. If I don't find a high ratio, then I'm not going to weld the diff, because I think that would make the engine dog even more than it already is....

Thanks for your time!!

--sarge
(no military affiliation, just a nickname I've had for years...)

[silicon212]

A 9C1 Caprice donor car is your best bet. These have 3.08 or 3.42 ratios, plus have 8.5" ring gears and will directly bolt into your car (and have the proper 5 on 5 bolt pattern).

Also, your car has a TH2004R transmission in it - the TH700R4 was only available for Chevrolet engines.

[SgtRauksauff]

Thanks!

I'd rather have something even higher, like a 3:7x or 3:9x, or even a 4.x or 5.x if possible, but I'm betting the higher the ratio, the lower the chances of finding one in this lifetime will be. I'll start looking for 9C1's asap.

I miss my caprice. I had an 83 classic, with a 305 that ended up with a siezed water pump and overheating, so i threw in a 350 4-bolt main from a '77 suburban. No cat, one glasspack, and a rather bald right rear tire was what that ended up to be... some extra HD springs from a 78 delta88, and some regular caprice HD springs in the back, with some S10 15x7 rims completed the mods to the car. Drove it solid for about 6 years, then I sold it to a buddy who needed a car badly, who promptly ditched it, wrecking the immaculate lines, then cracked the flexplate. he gave it to another buddy, who fixed the flexplate, then proceeded to wreck all of the forward gears. lol! I'm glad I got rid of it when I did.


--sarge

[GreyGoose006]

you might be better to look for rear ends from newer gm pickups in junkyards.
they mostly all have some kind of limited slip, and higher ratios and are pretty bullet proof.

[SgtRauksauff]

with a truck axle, though, I'd just have to pull the carrier and pinion, right, since the axles are a few inches wider than would be found in my wagon?

I need to take a tape measure and get off to the junkyards in the area....



--sarge

[GreyGoose006]

use the entire axle.
who cares if it sticks out a bit.
extra track will be good for you in the dirt

[silicon212]

Originally Posted by GreyGoose006

use the entire axle.
who cares if it sticks out a bit.
extra track will be good for you in the dirt

You can't do that. The truck axle is set up for leaf springs, and as such, there's no mounts for the upper control arms. You need to stick with the car housing.

Also, the rear tires on the wagons are covered - you can't stick the tires outboard of them without cutting a lot of metal from the body. Sedans had the covered wheel wells in '91-'92 whereas the wagons had them from '91 through '96.

Sarge -

As far as the carrier assembly, you can use a truck carrier in your car axle, provided they're both 8.5" and you get one from an '89 or later. The earlier axles have less splines on them than the '89-up ones do.

[SEVILLEMAN601]

hi, silicon. I have a 95 9c1 caprice with 5.7L V8 LT1. The car is really fast, but I know it could be faster. What all would you suggest to make it perform better? Also, can you tell me should I go with true duals or just get tips and mufflers since I already have factory dual exhausts? Do you know a good website to buy parts also? I just noticed that you have a 9c1 and I'm quite sure that you have upgraded some things under the hood. BTW... That chevy is clean!!! I wanted a 9c1 box chevy but all of the ones I saw were beat up so I decided to settle with my 3rd 9c1 bubble caprice. I had 2 93s and the 93s are nothing compared to this 95! Please let me know what you think.

[silicon212]

Originally Posted by SEVILLEMAN601

hi, silicon. I have a 95 9c1 caprice with 5.7L V8 LT1. The car is really fast, but I know it could be faster. What all would you suggest to make it perform better? Also, can you tell me should I go with true duals or just get tips and mufflers since I already have factory dual exhausts? Do you know a good website to buy parts also? I just noticed that you have a 9c1 and I'm quite sure that you have upgraded some things under the hood. BTW... That chevy is clean!!! I wanted a 9c1 box chevy but all of the ones I saw were beat up so I decided to settle with my 3rd 9c1 bubble caprice. I had 2 93s and the 93s are nothing compared to this 95! Please let me know what you think.

As for your car, I'd ask either Blue Bowtie or 96capricemgr as they are more experienced with the LT1 than I am. Having said that, I'd go with a catback exhaust system as the ones that come on the LT1 cars are kind of small. Tips are for show only - they do nothing for performance (despite what you may have heard). A reprogram of the PCM should wake it up a little, too. Again, Blue Bowtie would have the lowdown on that.

PS thanks for the compliment on the car. I've put a lot of work into it, perhaps more than its worth - but it's my car and I love it just the same.

[SgtRauksauff]

Originally Posted by silicon212

As far as the carrier assembly, you can use a truck carrier in your car axle, provided they're both 8.5" and you get one from an '89 or later. The earlier axles have less splines on them than the '89-up ones do.

Awesome, that's what I needed to know, thank you! I'm pretty sure I've got access to a couple different truck rears that have nice short ratios. I could weld on whatever I need to, and cut the fenders, but again, that would be just way to much work for a just-for-fun bomber.

by "covered tires" did you mean skirts, or the inner fenders?

here's a pic of how it sits right now; with the suburban rims, the offset (or backspacing, depending on what you want to call it) puts the track out about as far as it can go without having to massage the wheel arches...


--sarge

[silicon212]

Never mind the comment about the wheel wells - I for some reason, spaced out and figured you had a '95. I had you confused with the other guy.

[SgtRauksauff]

Ah, no problem. It's the internets. If they weren't so many pipes, it would be a lot easier...


--sarge