Rear diff and tranny arn't same final drive

[Karma]

Long story short I bought and installed what I was told was a "Galant" transmission. Now, after running the car while up on jackstands, ive realized the final drive ratio's are different.

1) I need to know if I can take the ring and pinion from the corresponding Galant rear diff, and swap them into my Talon's rear diff. Becuase swapping rear diff's completly require's more work. IE axles and the works.

2) If I can do that, what make/model of car will I need to get a rear diff from?

All I know about the tranny is as follows:
(under the barcode) *BHC8384_PH_J?_* The two _'s are worn off the bellhousing, and im not sure if the 2nd l;ast digit is a J

(nearest to the engine) C51PH & HC8384

This is also on a 1990 TSI AWD talon. 22 spline transfercase.

 

[brandonzero0]

Did you swap the t case from the galant trans or are you still using te talon t case?

 

[twinturbo3k]

The rear ends are the same in a Galant as a Talon/Eclipse/Laser. The only difference was a taller/weaker first gear. Also, I dont think you installed a galant trans, because I just put an early 91 TSi trans into my Galant and it will not bolt to my Galant transfer case because it is a 23 spline while early 91s still had the 22spline. I have to put in my 90 TCase for it to work. Im not sure what is going on with your car but you should not have been able to put that transmission onto a 90 transfer case if it was indeed a Galant transmission. Im speaking for the VR4, if it came from a Galant GSX I honestly dont know; that could be your problem, but im not even sure if a GSX trans will bolt up. Good luck and let us know how this turns out, im confizzled.

 

[Karma]

I used the transfer case from my Talon, becuase the "galant" tranny, and my transfer case were both 22 spline.


As for it not bolting up, I was quote "told" that it was from a 1990 Galant, therefore it had the 22 spline transfer case. As for it bolting up, everything lines up good. The shifter fork things on the tranny was a tiny bit different (1/4 inch), so I just put the one from the Talon's tranny onto the Galant. Everything seems to work, I got into all 5 gears when it was on jackstands.
Im just as confused as the next person, is the best way to find out final drive to just spin the input shaft one revolution, and see what the output shaft spins. Then do the same for the rear diff, then compare?

Any info on this subject would help.

 

[toybreaker]

I was hoping a wiseman would come along and answer this.

Simple questions like this drive me nuts. I've been driving along, finding myself thinking about how the wheel speeds on stands could be so visibally different. It's one of those really simple questions that has to have a good, technically correct answer.

That said, I'm not sure that running the car on stands is a good test for determining final drive compatability. With three differentials, there's all kinds of possibilities for a front wheel to be appear to be going mach 5, while the rears appear to be going much slower.

With an open front diff, one front wheel could spin full speed, and the other front may turn slower.

The center diff located in the transmission is an open diff, and it is the viscous coupler in the trans that ties the front and rear drivelines together thru the center diff. The coupler is hella stiff, but it will slip some. Depending on the health of the v.c, you might get substantial front/rear speed differences flying thru the air on stands.

And then there's the rear diff. It could be an open diff, or an lsd, depending on how the car was originally optioned. Look for an orange safety sticker in the drivers door jamb. There is also a sticker on the rear diff cover with the ratio, (hopefully 3.545) and lsd fitment. An open rear diff will allow the rears to spins at drastically different speeds side to side.

So, anyway, with all those differentials errr, ummm differentiating p ), there will be some speed differences.

I know, because your question made me curious, so I threw my 92 tsi up on the lift at work, and spun it up. The wheel speeds were visibally different. I drive this car every day, so I know the ratios match.

Anyway, I couldn't really come up with a definative answer, but I did play with it enough to make a few observations.

If you have open front and rear diffs, it's as easy as putting one side of the car up, so both wheels on that side are clear of the ground, mark the tires at tdc for a reference, and then spin the rear wheel, (by hand, engine off, in neutral) and watch the front. They should turn together, at the same speed, and the same number of turns. I checked my galant vr4 this way, (open front and rear diffs) and it was so simple and easy it was anti-climatic. I was visualising all kinds of math, and ratio calculations, etc, and just raising half the car told the tale in 30 seconds.

A rear lsd will make it a bit more challenging but, we were able to check my 92tsi, (With four bolt lsd) fairly easily with just a little help from my friends. With all four wheels up, (engine off, and the gearbox in neutral), you can try and sychronise the wheel speeds manually. If you get four people to each turn a wheel, you should be able to feel the driveline bind, (if the ratios are indeed different.) We used a 21mm socket on a breaker bar, on a lugnut at each wheel, marked the tire, and we turned them all together calling out when we went past tdc. We then tried to simulate a different rear drive ratio by slowing down the rear, and it binds up fast. It takes a bunch of force to slip the viscous coupler, and any difference in front to rear driveline speed will definately be felt at the wheels.

With all four of you turning the same speed for twenty turns or so, you should be able to determine a mismatch. The unloaded driveline is pretty easy to turn, and if you're fighting each other to turn the same speed, I would think it would be obvious

I would verify that the v.c. in the tranny is healthy by setting the handbrake, and trying to turn both the fronts counter-clockwise together. It should be very hard to slip the fronts, but if the coupler is healthy, you can sloooowly rotate the fronts relative to the rear. (please, use a torque wrench, set to ~80 ftlbs, or due caution to not strip the lugnut on the r/f) If the fronts rotate easily, the viscous coupler may be toasted, if they don't rotate at all, the center diff may be hashed.

As a final test, have your buddies hand push you once or twice around the parking lot. If it doesn't bind up/get really hard to push in a couple of hundred feet, you might just have gotten lucky.

Any mismatch in font/rear final drive ratios would definately heat the v.c up, so as a last check, I would feel the outside cover on the trans, (where the v.c lives), after a few hot laps around the block.

Remember, in addition to this being a jdm unit, this is a used trans. There's really no way to know if it's healthy. It could have been towed to the boneyard on the rear wheels, and the viscous coupling or center diff may have been damaged, for all we know. Or someone could have "modified" the internals, to match their set-up. Like we discussed in the other threads, it's a bit of a pig in a poke to buy a tranny sight unseen, so taking your time to verify what you got is definately a good plan.

Good luck, and please, update this thread. There's a couple of C51PH compatabilty threads open here and on the intraweb that just....... kind......... of..................... trail...................... off.............

It would be helpfull for future searchers to have a thread that shows the end result of putting a C51PH in a us market T/E/L.

 

[Karma]

I know it wasn't all for me, but thanks for taking the time to mess around with the car. Ive already done a few of those tests just by working on my car this winter. The day I got it running I was quite happy so I decided to take it around the block. I drove it about 1km in total, it definitly felt smooth, no binding thats for sure. I have also had it up off the floor(with e brake applied) and spun the front wheels. They spin, but it does require a fair amount of effort. The opposite wheels spins the opposite wheels as per usual. I haven't got enough willing hands to move all 4 wheels at once though, nor have I tried moving just one side of wheels like you said. Thats on the list for tomorrow.

Also! I searched on my rear diff yesterday for a sticker of sorts. Nothing to be found(although ill go back tomorrow and clean off the rear cover to see if it hides beneath the dirt). As for a LSD sticker on the door jamb, the previous owner repainted the car. So all stickers are gonzo.(finding a color match is near impossible. Its black with a purple flake) I was almost going to pull off the rear cover and count ring and pinion teeth. But my poor work ethic got the best of me.

Quote:
Originally Posted by Karma
Went today and checked the numbers, the one with the barcode above it reads:

*BHC8384_PHJ?_* I couldnt read the two _'s , and im not 100% sure if the 2nd last digit is a J.

As for the two other numbers scribed into the bellhousing:
C51PH & HC8384


I was thinking that instead of ripping out the transmission I have, I could just try and find a rear diff that will be compatable with the transmission. Do I have the right idea here?

Again, thanks for your help, not too many guys go out of their way for these kinds of questions.

Sean

That's a JDM 88-89 VR4 tranny. It has the same differential gear ratio as a U.S. VR4 and 1g awd dsm's, it should work just fine. See if there's a tag on the rear differential with the gear ratio printed on it. It should say 3.545

.

 

[talontd92tsi]

So this thread intrigued me, i know i remembered seeing something about GVR4 trannies not being compatible with t/e/l somewhere along the line. So, i go to vfaq.com and find this

http://www.vfaq.com/mods/Trannies.html

and this is what ive come up with

1g MT GVR-4
1-3.083 1-2.571
2-1.684 2-1.600
3-1.115 3-1.160
4-.833 4-.862
5-.666 5-.617
R-3.166 R-3.166

Now, none of that would really matter, now would it seeing that we regularly replace our first gear with a gvr-4 first to get us a few more mph in first for those 60' times.

heres where it gets interesting

Transfer case ratios

1g MT GVR-4
Primary gear 1.275 1.275
Secondary gear 3.866 <b>4.260</b>
Transfer gear 1.090 1.090

Final 4.929 <b>5.435</b>

Rear End 3.545 3.545

So it appears that the difference is in the final drive of the front diff, and the secondary gear in the transfer case, which im sure when combined together will work fine with the rear end in the car (seeing that its the same ratio) BUT if they arent matched you WILL break something, most likely the viscous coupling or the center diff.

 

[Karma]

When I opened up the transfer case, I counted both gears. I can't remember the numbers exactly, but after looking at the vfaq site, I can now recall that it was 24/22. IE. The ratio from my transfer case, is the same as what comes on the Galant, which is what I have in the car now. Same goes for the rear diff.

Hopefully..

PS: I was about to be able to rest easy tonight knowing that it was going to jive! But its good that you found that info. I didnt think to look on vfaq.

 

[talontd92tsi]

Well, from what i can tell its actually the final drive in the transmission that is different as well as one of the ratios in the transfer case, so when you combine those two parts, it meshes with the rear end ratio. So until you get a galant xfer case i wouldnt drive the car.

 

[boostnbuds]

uhh i didnt read this entire post and i dont have anything helpfull to say but driving your car while on jackstands is pretty wreckless and is bad for your axles/cv's

 

[JackM]

Maybe you should read the entire post, because there is some excellent info in here. Toybreakers post was really good, I have never tried it with 4 people, but we will have to You wouldn't believe how many people are driving on wrong front diff, rear diff, or t-case gear ratios. We had a customer come in with a rear end that caught on fire because of incorrect front and rear wheel ratios. He was running an early t-case in a late 98' trans. The VCU got really hot in the rear end and did some pretty nasty stuff! We run cars on the lift here all the time and it never bothered anything.

An easier way to check the t-case gear ratio is to:

1) mark the coupler (input) side of the t-cases location with the housing and mark the output end.

2) turn the input side 12 full revolutions. Did the output side mark line back up to where it was? If so, you have an 89-97ish t-case gear ratio. If not, try going another 2 revolutions for a total of 14 turns. If it lines up in 14 turns then you have the 97ish-99 t-case.

Jack
www.jackstransmissions.com

 

[Karma]

The car is driving fine, no lurching or anything. And after I drive for a while, I feel the transmission, and it is still cool. If the VC was spinning inside, it would be hot as hell.

 

[Nors]

Maybe you should read the entire post, because there is some excellent info in here. Toybreakers post was really good, I have never tried it with 4 people, but we will have to You wouldn't believe how many people are driving on wrong front diff, rear diff, or t-case gear ratios. We had a customer come in with a rear end that caught on fire because of incorrect front and rear wheel ratios. He was running an early t-case in a late 98' trans. The VCU got really hot in the rear end and did some pretty nasty stuff! We run cars on the lift here all the time and it never bothered anything.

An easier way to check the t-case gear ratio is to:

1) mark the coupler (input) side of the t-cases location with the housing and mark the output end.

2) turn the input side 12 full revolutions. Did the output side mark line back up to where it was? If so, you have an 89-97ish t-case gear ratio. If not, try going another 2 revolutions for a total of 14 turns. If it lines up in 14 turns then you have the 97ish-99 t-case.

Jack
www.jackstransmissions.com

Thanks for this post. Little tricks like that make shit way easier.

 

[JackM]

Yeah, I have a lot more info on tranny stuff I'd like to share, but I can't post in the drivetrain area because of this 'new member' thing that just won't go away for some reason... I thought I would have been a regular member by now

Jack

Thanks for this post. Little tricks like that make shit way easier.

 

[GVR4592]

Jack, I think the new system is based on the amount of posts you have and amount of time you have been a registered member. You probably just need more posts. You know if you become a supporting vendor, you get the "DSMtuners Supporting Vendor" title under your name. Just something to think about

 

[JackM]

Cool! I think we might do that. Thanks!

Jack
www.jackstransmissions.com

 

[cbassgsx]

I can verify that in a 90 with a 90 t case the c51ph is a good tranny. I put mine in at 180k and at 225k miles it still works great. no vc issues or differential issues to speak of.

 

[WatchItExplode]

1) I need to know if I can take the ring and pinion from the corresponding Galant rear diff, and swap them into my Talon's rear diff.

Can anybody answer the question from the original poster?

I've been searching through various threads to find out if I can take the gear out of my 3 bolt rear and put it in a 4-bolt rear from an automatic, that I just so happen to have. Can't find any answer.