Transmission question.

whooley · 03-25-2008, 06:20 PM

I'm hoping someone knows an answer to this.
I have a 92 Chevy 2500 4x2 with the 4 speed automatic. The tranny is shot.
What I want to do is use a TH400 like I have in my 89 GMC 2500 4x4.
I'm just not sure how the speedometer set up works.
Is it possible to use any Chevy TH400 and use the speedometer sending unit out of my 89 4x4?

Thanks in advance.

gmctrucks · 03-25-2008, 07:01 PM

Try Lucas trans addivtive do a goggle on it and see how many people have used it and how many people saved money by using it.

junior3382 · 03-27-2008, 12:46 PM

Quote:

Originally Posted by gmctrucks

Try Lucas trans addivtive do a goggle on it and see how many people have used it and how many people saved money by using it.

Are you saying this lucus oil will revive a dead tranny? That seems hard to believe.

o3shortbed · 03-27-2008, 02:03 PM

Quote:

Originally Posted by junior3382

Are you saying this lucus oil will revive a dead tranny? That seems hard to believe.

it wont. i tried it and it fried the 2 gears i had. as far as the th400 you will need to do some drive shaft mods. some 88 or 89 trucks came with a th400 so a speed sender and shafts shouldnt be too hard to find

tonyvt · 03-28-2008, 01:15 PM

there is no majic potion.....for anything.... especially trannys and engines..

If there only was!!!

gmctrucks · 03-29-2008, 08:27 PM

Well on a MPV that we still have but hardly use it because we up-dated to a newer model the trans was slipping bad I changed the fluid and added a bottle of Lucas and it stopped slipping if you do a goggle on it you can see comments that people have left that this stuff really works. Now if it's super messed up I doubt if it will fix it but it did me right. Good luck!

PAPA BEAR · 03-30-2008, 04:34 AM

if you swap to a 400 you will lose gas mileage 3spd verses 4spd why not rebuild

75K30 · 03-30-2008, 09:18 AM

A 92 2500 truck uses a Th700R4 right? This has a cable operated speedo just like the Th400, so there is no issue here. Calibration is the only thing that might be a problem.
Driveshaft length, slip yoke differences, shifter detents (your column has multiple points, and the three speed has one less, so the indicator will never be correct), the fact that that kickdown is cable oprerated, and the TH400 is done electrically, the Th 400 uses a vacuum modulator and the 700 does not.
You give up a real nice first gear (2.48 vs 3.06), and you give up OD, and the lock up feature.
If giving up all of this is worth it, then have at it, and good luck, but in my opinion, this is not worth the effort.
How many miles of operation did the 700 provide? If this thing lasted since 92, count your blessings and have it re-built. This way you minimize the fabrication time trying to get an older less desireable unit in there, and you can look foward to many additional years of use.
The 700 is not bad.

whooley · 04-01-2008, 05:37 PM

Thanks guys.
But I went a different route, I decided it wasn't worth the effort to make the swap. Instead I picked up a very nice 91 Chevy 1500 4x4 with the 5 speed manual. The 700R4 is the biggest piece of scrap I've ever seen. The 92 that I mention has 112,000 miles and has had the tranny rebuilt 2 times already and needs another. If I wanted to spend $1200 then I would use my TH400 and get an add on overdrive unit. The 89 with the TH400 has 254,000 miles and the tranny has never been touched other than maybe 2 filter changes, it outlasted the original engine and i'm sure would oulast the replacement crate engine as well. It's a matter of fuel savings over reliability no different than buying a truck with a large V8 vs a V6 because you need the power.

Both the 89 and 92 have electric speedometers, no cable. My reason for asking is because I can find no reference to the 400 ever being electric only, even when named 3L80.
Also the shift detents are in the tranny not the steering column so that wasn't an issue, neither was the correctness of the indicator although it is easily swapped. Driveshaft work doesn't bother me, it's fairly cheap.

As far as fuel milage, I was perfectly happy driving my 89 Sierra 4x4 with no overdrive(10 mpg average, not bad cost wise for a 19 year old truck considering what most newer trucks with OD get..) while my friend who owns the 92 Chevy had it in the shop for tranny work, then a tranny rebuild, then more tranny work. It's now ready for another tranny rebuild or atleast more work and my 89 is only parked because it's body is rotten away(it spent most of it's life with a snow plow and salt spreader) and it needs new tires, 31x10.5x16.5's are nearly impossible to find do to wheel size...She was a great dependable truck and it payed for itself 100 times over but it needed too much work. I just hope the new truck will do the same.

I realize that some/very few people have had good luck with the 700R4 and it's variants but I've had alot of experience with cars, trucks and vans that use them and I don't care for them and will not own another vehicle with it. The TH400 is just a dependable tranny, if GM would have used it as a base for their overdrive tranny they wouldn't have had problems. They were just too worried about saving weight.

03-25-2008, 06:20 PM	#1
whooley Junior Member Join Date: Mar 2008 Posts: 9	Transmission question. I'm hoping someone knows an answer to this. I have a 92 Chevy 2500 4x2 with the 4 speed automatic. The tranny is shot. What I want to do is use a TH400 like I have in my 89 GMC 2500 4x4. I'm just not sure how the speedometer set up works. Is it possible to use any Chevy TH400 and use the speedometer sending unit out of my 89 4x4? Thanks in advance.

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03-25-2008, 07:01 PM	#2
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 1,959	Try Lucas trans addivtive do a goggle on it and see how many people have used it and how many people saved money by using it.

03-28-2008, 01:15 PM	#5
tonyvt Full Member Join Date: Dec 2007 Posts: 12	there is no majic potion.....for anything.... especially trannys and engines.. If there only was!!!

03-29-2008, 08:27 PM	#6
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 1,959	Well on a MPV that we still have but hardly use it because we up-dated to a newer model the trans was slipping bad I changed the fluid and added a bottle of Lucas and it stopped slipping if you do a goggle on it you can see comments that people have left that this stuff really works. Now if it's super messed up I doubt if it will fix it but it did me right. Good luck!

03-30-2008, 04:34 AM	#7
PAPA BEAR Senior Member Join Date: Mar 2008 Location: North Carolina Posts: 112	if you swap to a 400 you will lose gas mileage 3spd verses 4spd why not rebuild

03-30-2008, 09:18 AM	#8
75K30 Senior Member Join Date: Jul 2006 Posts: 2,627	A 92 2500 truck uses a Th700R4 right? This has a cable operated speedo just like the Th400, so there is no issue here. Calibration is the only thing that might be a problem. Driveshaft length, slip yoke differences, shifter detents (your column has multiple points, and the three speed has one less, so the indicator will never be correct), the fact that that kickdown is cable oprerated, and the TH400 is done electrically, the Th 400 uses a vacuum modulator and the 700 does not. You give up a real nice first gear (2.48 vs 3.06), and you give up OD, and the lock up feature. If giving up all of this is worth it, then have at it, and good luck, but in my opinion, this is not worth the effort. How many miles of operation did the 700 provide? If this thing lasted since 92, count your blessings and have it re-built. This way you minimize the fabrication time trying to get an older less desireable unit in there, and you can look foward to many additional years of use. The 700 is not bad.

04-01-2008, 05:37 PM	#9
whooley Junior Member Join Date: Mar 2008 Posts: 9	Thanks guys. But I went a different route, I decided it wasn't worth the effort to make the swap. Instead I picked up a very nice 91 Chevy 1500 4x4 with the 5 speed manual. The 700R4 is the biggest piece of scrap I've ever seen. The 92 that I mention has 112,000 miles and has had the tranny rebuilt 2 times already and needs another. If I wanted to spend $1200 then I would use my TH400 and get an add on overdrive unit. The 89 with the TH400 has 254,000 miles and the tranny has never been touched other than maybe 2 filter changes, it outlasted the original engine and i'm sure would oulast the replacement crate engine as well. It's a matter of fuel savings over reliability no different than buying a truck with a large V8 vs a V6 because you need the power. Both the 89 and 92 have electric speedometers, no cable. My reason for asking is because I can find no reference to the 400 ever being electric only, even when named 3L80. Also the shift detents are in the tranny not the steering column so that wasn't an issue, neither was the correctness of the indicator although it is easily swapped. Driveshaft work doesn't bother me, it's fairly cheap. As far as fuel milage, I was perfectly happy driving my 89 Sierra 4x4 with no overdrive(10 mpg average, not bad cost wise for a 19 year old truck considering what most newer trucks with OD get..) while my friend who owns the 92 Chevy had it in the shop for tranny work, then a tranny rebuild, then more tranny work. It's now ready for another tranny rebuild or atleast more work and my 89 is only parked because it's body is rotten away(it spent most of it's life with a snow plow and salt spreader) and it needs new tires, 31x10.5x16.5's are nearly impossible to find do to wheel size...She was a great dependable truck and it payed for itself 100 times over but it needed too much work. I just hope the new truck will do the same. I realize that some/very few people have had good luck with the 700R4 and it's variants but I've had alot of experience with cars, trucks and vans that use them and I don't care for them and will not own another vehicle with it. The TH400 is just a dependable tranny, if GM would have used it as a base for their overdrive tranny they wouldn't have had problems. They were just too worried about saving weight.